Elecraft

Re: K3 AF knob..

Classic

List

Threaded

40 messages Options

K9MA

Re: Field Day rig experience

I think the LO phase noise should be pretty close.

----------

Scott Ellington. K9MA

--- via iPhone

> On Jun 10, 2018, at 1:17 PM, Jim Brown <[hidden email]> wrote:
>
>> On 6/9/2018 12:54 PM, K9MA wrote:
>>> On 6/9/2018 14:52, David Gilbert wrote:
>>> I think another major concern for closely positioned rigs would be transmitted phase noise, and of course that doesn't show up in the Sherwood charts.
>>
>> Yes, it does!
>
> All I've ever seen from Rob is RX phase noise. Can you provide a link to TX phase noise? The TX phase noise data I've published came from ARRL Labs.
>
> 73, Jim K9YC
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

David Gilbert

Re: Field Day rig experience

In reply to this post by Jim Brown-10

I couldn't find any data on transmit phase noise on the Sherwood web
site either, and I searched all over for it.

Dave AB7E

On 6/10/2018 11:17 AM, Jim Brown wrote:

> On 6/9/2018 12:54 PM, K9MA wrote:
>> On 6/9/2018 14:52, David Gilbert wrote:
>>> I think another major concern for closely positioned rigs would be
>>> transmitted phase noise, and of course that doesn't show up in the
>>> Sherwood charts.
>>
>> Yes, it does!
>
> All I've ever seen from Rob is RX phase noise. Can you provide a link
> to TX phase noise? The TX phase noise data I've published came from
> ARRL Labs.
>
> 73, Jim K9YC

gm3sek

Re: Field Day rig experience

In reply to this post by K9MA

>I think the LO phase noise should be pretty close.

Perhaps it *should* be... but some of the worst examples of wideband
transmitted noise are caused by additional amplitude noise in the TX
chain, or by poorly filtered DAC noise in SDR-based transceivers
[1]. These noise sources are additional to the LO noise, and are
present whenever the rig is in TX mode (even without modulation).

That unfounded *belief* that "the LO phase noise should be pretty
close" was precisely the reason why none of the designers paid any
attention to the excess transmitter noise. But the equipment reviews
were equally at fault for failing to draw attention to the problem.

[1] Band Pollution from Amateur Transmitters - SM5BSZ
http://sm5bsz.com/dynrange/dubus313.pdf

73 from Ian GM3SEK

>-----Original Message-----
>From: [hidden email] [mailto:elecraft-
>[hidden email]] On Behalf Of K9MA
>Sent: 10 June 2018 20:14
>To: [hidden email]
>Cc: [hidden email]
>Subject: Re: [Elecraft] Field Day rig experience
>
>I think the LO phase noise should be pretty close.
>
>----------
>
>Scott Ellington. K9MA
>
> --- via iPhone
>
>> On Jun 10, 2018, at 1:17 PM, Jim Brown
><[hidden email]> wrote:
>>
>>> On 6/9/2018 12:54 PM, K9MA wrote:
>>>> On 6/9/2018 14:52, David Gilbert wrote:
>>>> I think another major concern for closely positioned rigs would

be
>transmitted phase noise, and of course that doesn't show up in the
>Sherwood charts.
>>>
>>> Yes, it does!
>>
>> All I've ever seen from Rob is RX phase noise. Can you provide a
link
>to TX phase noise? The TX phase noise data I've published came
from

>ARRL Labs.
>>
>> 73, Jim K9YC
>>
>>
>__________________________________________________________
>____
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list:

http://www.qsl.net/donate.html

>> Message delivered to [hidden email]
>
>__________________________________________________________
>____
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:[hidden email]
>
>This list hosted by: http://www.qsl.net
>Please help support this email list: http://www.qsl.net/donate.html
>Message delivered to [hidden email]

wayne burdick

Re: Field Day rig experience

Administrator

In reply to this post by David Gilbert

The K3S has exceptionally low TX phase noise and high RMDR. Both are due to the new synth. The rest of the signal chain is also very clean.

You have to get this right on both RX and TX to optimize for close-proximity, multi-transmitter operation (e.g. Field Day, DXpeditions, and big contest stations).

73,
Wayne
N6KR

----
http://www.elecraft.com

> On Jun 10, 2018, at 12:55 PM, David Gilbert <[hidden email]> wrote:
>
>
> I couldn't find any data on transmit phase noise on the Sherwood web site either, and I searched all over for it.
>
> Dave AB7E
>
>
>
>> On 6/10/2018 11:17 AM, Jim Brown wrote:
>>> On 6/9/2018 12:54 PM, K9MA wrote:
>>>> On 6/9/2018 14:52, David Gilbert wrote:
>>>> I think another major concern for closely positioned rigs would be transmitted phase noise, and of course that doesn't show up in the Sherwood charts.
>>>
>>> Yes, it does!
>>
>> All I've ever seen from Rob is RX phase noise. Can you provide a link to TX phase noise? The TX phase noise data I've published came from ARRL Labs.
>>
>> 73, Jim K9YC
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

alorona

Re: Field Day rig experience

In reply to this post by Paul Antos

If you do take the icom, at 3.5A receive current drain you'd better take two extra batteries, too.

Al W6LX

>> Take the K3 , leave the IC-7610 at home. It’s to darn heavy to lug around. (19 lbs )

>>NS2N
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

wayne burdick

Re: Field Day rig experience

Administrator

Yes. The K3 is intended to be operable from a battery or solar panel, and it’s receive-mode current drain is about 1 amp (a little higher with the sub receiver turned on).

73,
Wayne
N6KR

> On Jun 10, 2018, at 3:46 PM, Al Lorona <[hidden email]> wrote:
>
> If you do take the icom, at 3.5A receive current drain you'd better take two extra batteries, too.
>
> Al W6LX
>
>
>
>>> Take the K3 , leave the IC-7610 at home. It’s to darn heavy to lug around. (19 lbs )
>
>
>>> NS2N
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

Jim Brown-10

Re: Field Day rig experience

In reply to this post by alorona

On 6/10/2018 3:46 PM, Al Lorona wrote:
> If you do take the icom, at 3.5A receive current drain you'd better take two extra batteries, too.

And don't overlook the HUGE KX2 and KX3 advantage of only 150 mA battery
drain on receive, as compared to about 1A for a single RX K3/K3S.

73, Jim K9YC

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

WILLIE BABER

Re: Field Day rig experience

In reply to this post by Bill-4

More then one so2r operator has noted that the 7300 will overload in an so2r situation so that you cannot clearly hear on 7300 when the other radio is transmitting (yes, on a different band). Since the 7610 doesn't have a front-end either, I imagine that it will do the same. Sherwood himself notes that using the SDR radio (i.e, without a superhet front-end) means reducing gain to limit ADC overload, but he has also suggested that blocking dynamic range is over-rated. Generally this is true, dynamic range is over-rated if you are using one radio. However, blocking isn't over-rated in a field day situation (more than one radio) or if you have a neighboring op running high power, or in legal-limit multi-op situations (with antennas relatively close to each other), or in legal-limit so2r.

Reducing sensitivity works to prevent ADC overload on the lower bands where sensitivity is not needed in the first place but on 15m through 6m one can use the sensitivity. While SDR radios have their advantages, some of the advantages of superhet radios still exist today, namely, that a so-called roofing filter front-end (which is just a mode-specific filter ahead of the first mixer) will deliver outstanding blocking AND as much sensitivity as required (compared to SDR).

I don't see any way around this fact (at least not yet) and you can see the difference in the Sherwood numbers.

73, Will, wj9b

CWops #1085
CWA Advisor levels II and III
http://cwops.org/

--------------------------------------------
On Sat, 6/9/18, Wayne Burdick <[hidden email]> wrote:

Subject: Re: [Elecraft] Field Day rig experience
To: "Bill" <[hidden email]>
Cc: "Elecraft Reflector" <[hidden email]>
Date: Saturday, June 9, 2018, 10:34 AM

> On Jun 9,
2018, at 5:24 AM, Bill <[hidden email]>
wrote:
>
> Along the
line (lightly discussed under "K3- AF Knob") of
what rigs are used for dxpeditions and Field Day...... How
do the new technology ICOMs (7300 and 7610) do under the
"several rigs on the same band" conditions? The
size, weight, and cost factor is inviting for the 7300 -
BUT!!! Is it up to the job? Close to up to the job? Or,
better left home during these events?

Hi Bill,

Hopefully you’ll get some responses to this
question from those with direct experience. But looking at
it theoretically: both the 7300 and 7610 are direct-sampling
radios with about 25-30 dB less blocking dynamic range than
the K3 or K3S. On Field Day this could have a definite
impact when using multiple transmitters on the same band, or
even on different bands, depending on antenna spacing and
power level used.

Dynamic
range of all of these radios is quantified in the receiver
performance table at www.sherweng.com, specifically the
fifth column (“100 kHz Blocking”).

Wayne

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

RobertG

Re: Field Day rig experience

Will...

A small nit... perhaps my ignorance... but, I think that the roofing
filter [by whatever name] comes after the first mixer, at the so-called
IF frequency. Your points are well made. I think the far out SDR's speak
more to what can conceivably be done versus what's the design approach
that best meets a broad range of desirable receiver parameters. Elecraft
seems to have found the sweet spot in the battle of trade offs.

...robert

On 6/12/2018 15:49, WILLIE BABER wrote:

> More then one so2r operator has noted that the 7300 will overload in an so2r situation so that you cannot clearly hear on 7300 when the other radio is transmitting (yes, on a different band). Since the 7610 doesn't have a front-end either, I imagine that it will do the same. Sherwood himself notes that using the SDR radio (i.e, without a superhet front-end) means reducing gain to limit ADC overload, but he has also suggested that blocking dynamic range is over-rated. Generally this is true, dynamic range is over-rated if you are using one radio. However, blocking isn't over-rated in a field day situation (more than one radio) or if you have a neighboring op running high power, or in legal-limit multi-op situations (with antennas relatively close to each other), or in legal-limit so2r.
>
> Reducing sensitivity works to prevent ADC overload on the lower bands where sensitivity is not needed in the first place but on 15m through 6m one can use the sensitivity. While SDR radios have their advantages, some of the advantages of superhet radios still exist today, namely, that a so-called roofing filter front-end (which is just a mode-specific filter ahead of the first mixer) will deliver outstanding blocking AND as much sensitivity as required (compared to SDR).
>
> I don't see any way around this fact (at least not yet) and you can see the difference in the Sherwood numbers.
>
> 73, Will, wj9b
>
> CWops #1085
> CWA Advisor levels II and III
> http://cwops.org/
>
> --------------------------------------------
> On Sat, 6/9/18, Wayne Burdick <[hidden email]> wrote:
>
> Subject: Re: [Elecraft] Field Day rig experience
> To: "Bill" <[hidden email]>
> Cc: "Elecraft Reflector" <[hidden email]>
> Date: Saturday, June 9, 2018, 10:34 AM
>
>
> > On Jun 9,
> 2018, at 5:24 AM, Bill <[hidden email]>
> wrote:
> >
> > Along the
> line (lightly discussed under "K3- AF Knob") of
> what rigs are used for dxpeditions and Field Day...... How
> do the new technology ICOMs (7300 and 7610) do under the
> "several rigs on the same band" conditions? The
> size, weight, and cost factor is inviting for the 7300 -
> BUT!!! Is it up to the job? Close to up to the job? Or,
> better left home during these events?
>
>
> Hi Bill,
>
> Hopefully you’ll get some responses to this
> question from those with direct experience. But looking at
> it theoretically: both the 7300 and 7610 are direct-sampling
> radios with about 25-30 dB less blocking dynamic range than
> the K3 or K3S. On Field Day this could have a definite
> impact when using multiple transmitters on the same band, or
> even on different bands, depending on antenna spacing and
> power level used.
>
> Dynamic
> range of all of these radios is quantified in the receiver
> performance table at www.sherweng.com, specifically the
> fifth column (“100 kHz Blocking”).
>
> Wayne
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

--
Robert G Strickland, PhD ABPH - KE2WY
[hidden email]
Syracuse, New York, USA
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Jim Brown-10

Re: Field Day rig experience

On 6/12/2018 4:50 PM, Robert G Strickland wrote:
> A small nit... perhaps my ignorance... but, I think that the roofing
> filter [by whatever name] comes after the first mixer, at the
> so-called IF frequency.

A month or so ago, as part of a project to measure input Z of receivers
and preamps, I measured the 2nd RX of my K3 as 50 ohms and with a
bandpass filter between the antenna input and the 50 ohm load. Clearly,
in the K3, there is a "per band" bandpass filter ahead of the first RF
stage.

73, Jim K9YC

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

WILLIE BABER

Re: Field Day rig experience

In reply to this post by Bill-4

Robert is talking about the crystal filters, also known as roofing filters now-days, that are typically placed after the first mixer (I mistakenly typed "ahead" but I meant "after" as Robert notes), though there is a post amp and NB before these filters in K2 and K3.

The idea is that a crystal filter right after the first mixer gives high dynamic range because high selectivity comes before the receiver has developed stages of gain that otherwise could cause blocking or IMD, especially when selectivity is postponed to the second mixer while ignoring gain distribution in prior stages of the receiver. This basic idea was popularized in Solid State Design for the Radio Amateur, and it was applied to Ten-Tec radios for decades (at a 9 mhz I-F).

Roofing filter gets defined in relationship to Japanese radios that had up conversion 15 khz filters at the first I-F, and generally lower dynamic range as a result, (but you got all modes, general coverage, and optional crystal filters at the second I-F).

Good for everyone radios.... but with lower dynamic range and phase noise from the early synthesizers. This is why Ten-Tec radios were so popular among contesters, especially Omni V and VI (modified with a narrow cw filter at the first I-F).

73, Will, wj9b

CWops #1085
CWA Advisor levels II and III
http://cwops.org/

--------------------------------------------
On Wed, 6/13/18, Jim Brown <[hidden email]> wrote:

Subject: Re: [Elecraft] Field Day rig experience
To: [hidden email]
Date: Wednesday, June 13, 2018, 10:36 AM

On 6/12/2018 4:50 PM, Robert G
Strickland wrote:
> A small nit...
perhaps my ignorance... but, I think that the roofing
> filter [by whatever name] comes after the
first mixer, at the
> so-called IF
frequency.

A month or so
ago, as part of a project to measure input Z of receivers

and preamps, I measured the 2nd RX of my K3
as 50 ohms and with a
bandpass filter
between the antenna input and the 50 ohm load. Clearly,
in the K3, there is a "per band"
bandpass filter ahead of the first RF
stage.

73, Jim
K9YC

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

wayne burdick

Re: Field Day rig experience

Administrator

Exactly right, Will. In the K3/K3S, we have a very strong mixer and post amp followed by crystal filters at the first I.F., 8.215 MHz. Since the IF and ADC are down-stream from these filters, they are very well protected from out-of-band signals.

Our crystal filters are manufactured to very tight tolerances and as a result, provide consistently high dynamic range.

The P3 panadapter gets its signal ahead of the crystal filters so it can display a wide spectrum. It is in effect a direct-sampling SDR in its own right.

The beauty of having the panadapter’s receiver chain (P3) fully separate from the demodulation receive chain (K3) is that demodulation remains unaffected (up to very signal levels) even if the panadapter has to separately reduce its own gain. “Pure” SDRs (IC7300, IC7610, Flex) don’t have this luxury; everything runs from the same wideband ADC, without narrowband protection via crystal filters.

Another K3/K3S advantage is in its very narrow ham-band RF filters. These are positioned ahead of the P3 pickoff point, benefitting both the panadapter and demodulation channels.

73,
Wayne
N6KR

> On Jun 13, 2018, at 11:38 AM, WILLIE BABER <[hidden email]> wrote:
>
> Robert is talking about the crystal filters, also known as roofing filters now-days, that are typically placed after the first mixer (I mistakenly typed "ahead" but I meant "after" as Robert notes), though there is a post amp and NB before these filters in K2 and K3.
>
> The idea is that a crystal filter right after the first mixer gives high dynamic range because high selectivity comes before the receiver has developed stages of gain that otherwise could cause blocking or IMD, especially when selectivity is postponed to the second mixer while ignoring gain distribution in prior stages of the receiver. This basic idea was popularized in Solid State Design for the Radio Amateur, and it was applied to Ten-Tec radios for decades (at a 9 mhz I-F).
>
> Roofing filter gets defined in relationship to Japanese radios that had up conversion 15 khz filters at the first I-F, and generally lower dynamic range as a result, (but you got all modes, general coverage, and optional crystal filters at the second I-F).
>
> Good for everyone radios.... but with lower dynamic range and phase noise from the early synthesizers. This is why Ten-Tec radios were so popular among contesters, especially Omni V and VI (modified with a narrow cw filter at the first I-F).
>
> 73, Will, wj9b
>
>
>
> CWops #1085
> CWA Advisor levels II and III
> http://cwops.org/
>
> --------------------------------------------
> On Wed, 6/13/18, Jim Brown <[hidden email]> wrote:
>
> Subject: Re: [Elecraft] Field Day rig experience
> To: [hidden email]
> Date: Wednesday, June 13, 2018, 10:36 AM
>
> On 6/12/2018 4:50 PM, Robert G
> Strickland wrote:
>> A small nit...
> perhaps my ignorance... but, I think that the roofing
>> filter [by whatever name] comes after the
> first mixer, at the
>> so-called IF
> frequency.
>
> A month or so
> ago, as part of a project to measure input Z of receivers
>
> and preamps, I measured the 2nd RX of my K3
> as 50 ohms and with a
> bandpass filter
> between the antenna input and the 50 ohm load. Clearly,
> in the K3, there is a "per band"
> bandpass filter ahead of the first RF
> stage.
>
> 73, Jim
> K9YC
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

Wes Stewart-2

Re: Field Day rig experience

In reply to this post by WILLIE BABER

Certainly not to disparage the K3(S) architecture (I have two of them) there is
nothing inherently wrong with an up-conversion receiver, if modern hardware is used.

See: https://martein.home.xs4all.nl/pa3ake/hmode/g3sbi_intro.html

and my friend Cornell's, Star-10 transceiver.
https://pdfs.semanticscholar.org/eb33/5c12858779a653d9b9b93ca20120aebb7616.pdf

Wes N7WS

On 6/13/2018 11:38 AM, WILLIE BABER wrote:

> Robert is talking about the crystal filters, also known as roofing filters now-days, that are typically placed after the first mixer (I mistakenly typed "ahead" but I meant "after" as Robert notes), though there is a post amp and NB before these filters in K2 and K3.
>
> The idea is that a crystal filter right after the first mixer gives high dynamic range because high selectivity comes before the receiver has developed stages of gain that otherwise could cause blocking or IMD, especially when selectivity is postponed to the second mixer while ignoring gain distribution in prior stages of the receiver. This basic idea was popularized in Solid State Design for the Radio Amateur, and it was applied to Ten-Tec radios for decades (at a 9 mhz I-F).
>
> Roofing filter gets defined in relationship to Japanese radios that had up conversion 15 khz filters at the first I-F, and generally lower dynamic range as a result, (but you got all modes, general coverage, and optional crystal filters at the second I-F).
>
> Good for everyone radios.... but with lower dynamic range and phase noise from the early synthesizers. This is why Ten-Tec radios were so popular among contesters, especially Omni V and VI (modified with a narrow cw filter at the first I-F).
>
> 73, Will, wj9b
>

WILLIE BABER

Re: Field Day rig experience

In reply to this post by Bill-4

Hello Wes,

I took a look. Both designs are using the idea of "roofing filter" to refer to up-conversion radios similar to the use of up-conversion 3khz filters as roofing filters in Icom radios.

"Roofing filter" (a mode specific filter after the first mixer including narrow cw filters) only makes sense in the context of the history of superhet design and in particular the use of one broad 15 khz first I-F (so that all modes may pass through it) typical of all Japanese radios until recently. Calling a 45 mhz filter at the first I-F a "roofing filter" as noted in the info you sent entirely misses the point of what roofing filter means. Or, to put it another way, all Ten-Tec radios had roofing filters in them (and were ssb and cw only) well before the term roofing filter was coined! Which is why an Omni C will out perform any wide (15 khz) first I-F Japanese radio, even those built well after the 1980 vintage Omni C.

Unless mode specific up-conversion crystal filters can be made and as narrow as 200 hz (this is possible with down-conversion) then "roofing filter" and up conversion doesn't make sense historically or in reality.

Actually, Icom says that did it with 1.2khz filter at 64 mhz in the Icom 7851, though I'm not convinced the filter is that narrow, and 1.2khz is far from the 200hz filter that my K3 has in it (however, the placement of this filter is why the 7851 is among the best radios in Sherwood's chart, on cw).

It is possible to make very narrow and precise crystal filters as narrow as the 200 hz inexpensively, and this is the point of having multiple roofing filters at the first I-F. So, this is the origin of the term roofing filter---in comparison to the barn-door up conversion first I-F.

73, Will, wj9b

CWops #1085
CWA Advisor levels II and III
http://cwops.org/

--------------------------------------------
On Wed, 6/13/18, Wes Stewart <[hidden email]> wrote:

Subject: Re: [Elecraft] Field Day rig experience
To: [hidden email]
Date: Wednesday, June 13, 2018, 3:08 PM

Certainly not to disparage the
K3(S) architecture (I have two of them) there is
nothing inherently wrong with an up-conversion
receiver, if modern hardware is used.

See: https://martein.home.xs4all.nl/pa3ake/hmode/g3sbi_intro.html

and my friend Cornell's,
Star-10 transceiver.
https://pdfs.semanticscholar.org/eb33/5c12858779a653d9b9b93ca20120aebb7616.pdf

Wes N7WS

On 6/13/2018 11:38 AM, WILLIE BABER
wrote:
> Robert is talking about the
crystal filters, also known as roofing filters now-days,
that are typically placed after the first mixer (I
mistakenly typed "ahead" but I meant
"after" as Robert notes), though there is a post
amp and NB before these filters in K2 and K3.
>
> The idea is that a
crystal filter right after the first mixer gives high
dynamic range because high selectivity comes before the
receiver has developed stages of gain that otherwise could
cause blocking or IMD, especially when selectivity is
postponed to the second mixer while ignoring gain
distribution in prior stages of the receiver. This basic
idea was popularized in Solid State Design for the Radio
Amateur, and it was applied to Ten-Tec radios for decades
(at a 9 mhz I-F).
>
>
Roofing filter gets defined in relationship to Japanese
radios that had up conversion 15 khz filters at the first
I-F, and generally lower dynamic range as a result, (but you
got all modes, general coverage, and optional crystal
filters at the second I-F).
>
> Good for everyone radios.... but with
lower dynamic range and phase noise from the early
synthesizers. This is why Ten-Tec radios were so popular
among contesters, especially Omni V and VI (modified with a
narrow cw filter at the first I-F).
>
> 73, Will, wj9b
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Elecraft mailing list

Re: Field Day rig experience

Hi Guys.

For what it's worth, I find it interesting how the term "Roofing filter" has changed a bit over time and with different 'ownership'.

Personally, I first came across the term in around 1966 as a junior design engineer working on the Redifon R550 series of HF receivers. I understood then that the term "roof" referred to the "top of the house" filter used to provide the first measure of protection against adjacent unwanted signals.

These and other similar HF receivers used an up-conversion architecture, and the R550/551 employed a first IF at 38 MHz with the local oscillator running 38 to 68 MHz. The bandwidth of this filter, which followed the first mixer, was around 15 KHz as I recall. The second IF was at 1.4 MHz (or 1.6 MHz in other similar designs) and featured a number of selectable crystal filters typically providing close-in band-widths from around 200Hz to 12 KHz. Employing a first IF above 30 MHz shifts the first image into the VHF spectrum and allows the use of a 30 MHz low pass filter in the front end, with sub-octave band pass filters to provide a measure of front-end selectivity. We would have loved to provide close-in selectivity at the first IF frequency and so avoid a down-conversion to the second IF, but achieving the required passband /stopband characteristics just was (is) not possible at 38 MHz. However, decent close in selectivity (passband and stopband) can be provided with cr
ystal filters at around 9 MHz or thereabouts, and many of the earlier purely analogue designs of amateur equipment took advantage of this, including TenTec. I do not personally view this particular application as a roofing filter as is not protecting further stages of selectivity.t it All now ancient history...things have moved on a bit since then! Can anyone trace the term further back in time?

However, It seems to me that the term "roofing filter" still makes perfectly good sense in the context of the K3 design, with the selectable crystal filters providing the maximum possible (mode dependent) selectivity protection in front of the final IF, even if that is now implemented using DSP techniques!

Terry
G3VFO
-----Original Message-----
From: [hidden email] <[hidden email]> On Behalf Of WILLIE BABER
Sent: 14 June 2018 16:02
To: [hidden email]; Wes Stewart <[hidden email]>
Subject: Re: [Elecraft] Field Day rig experience

Hello Wes,

I took a look. Both designs are using the idea of "roofing filter" to refer to up-conversion radios similar to the use of up-conversion 3khz filters as roofing filters in Icom radios.

"Roofing filter" (a mode specific filter after the first mixer including narrow cw filters) only makes sense in the context of the history of superhet design and in particular the use of one broad 15 khz first I-F (so that all modes may pass through it) typical of all Japanese radios until recently. Calling a 45 mhz filter at the first I-F a "roofing filter" as noted in the info you sent entirely misses the point of what roofing filter means. Or, to put it another way, all Ten-Tec radios had roofing filters in them (and were ssb and cw only) well before the term roofing filter was coined! Which is why an Omni C will out perform any wide (15 khz) first I-F Japanese radio, even those built well after the 1980 vintage Omni C.

Unless mode specific up-conversion crystal filters can be made and as narrow as 200 hz (this is possible with down-conversion) then "roofing filter" and up conversion doesn't make sense historically or in reality.

Actually, Icom says that did it with 1.2khz filter at 64 mhz in the Icom 7851, though I'm not convinced the filter is that narrow, and 1.2khz is far from the 200hz filter that my K3 has in it (however, the placement of this filter is why the 7851 is among the best radios in Sherwood's chart, on cw).

It is possible to make very narrow and precise crystal filters as narrow as the 200 hz inexpensively, and this is the point of having multiple roofing filters at the first I-F. So, this is the origin of the term roofing filter---in comparison to the barn-door up conversion first I-F.

73, Will, wj9b

CWops #1085
CWA Advisor levels II and III
http://cwops.org/

--------------------------------------------
On Wed, 6/13/18, Wes Stewart <[hidden email]> wrote:

Subject: Re: [Elecraft] Field Day rig experience
To: [hidden email]
Date: Wednesday, June 13, 2018, 3:08 PM

Certainly not to disparage the
K3(S) architecture (I have two of them) there is nothing inherently wrong with an up-conversion receiver, if modern hardware is used.

See: https://martein.home.xs4all.nl/pa3ake/hmode/g3sbi_intro.html

and my friend Cornell's,
Star-10 transceiver.
https://pdfs.semanticscholar.org/eb33/5c12858779a653d9b9b93ca20120aebb7616.pdf

Wes N7WS

On 6/13/2018 11:38 AM, WILLIE BABER
wrote:
> Robert is talking about the
crystal filters, also known as roofing filters now-days, that are typically placed after the first mixer (I mistakenly typed "ahead" but I meant "after" as Robert notes), though there is a post amp and NB before these filters in K2 and K3.
>
> The idea is that a
crystal filter right after the first mixer gives high dynamic range because high selectivity comes before the receiver has developed stages of gain that otherwise could cause blocking or IMD, especially when selectivity is postponed to the second mixer while ignoring gain distribution in prior stages of the receiver. This basic idea was popularized in Solid State Design for the Radio Amateur, and it was applied to Ten-Tec radios for decades (at a 9 mhz I-F).
>
>
Roofing filter gets defined in relationship to Japanese radios that had up conversion 15 khz filters at the first I-F, and generally lower dynamic range as a result, (but you got all modes, general coverage, and optional crystal filters at the second I-F).
>
> Good for everyone radios.... but with lower dynamic range and phase noise from the early synthesizers. This is why Ten-Tec radios were so popular among contesters, especially Omni V and VI (modified with a narrow cw filter at the first I-F).
>
> 73, Will, wj9b
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] ______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email]

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Wes Stewart-2

Re: Field Day rig experience

In reply to this post by WILLIE BABER

Will,

First of all I have said before and will repeat it, I detest the term "roofing
filter." That said, by the generally accepted definition, you are wrong. See
Elecraft's take on this:

http://www.elecraft.com/K3/Roofing_Filters.htm

If you will think in Wayne's terms, the post-mixer filter is a "protective"
filter, not a mode-specific filter. So the question becomes, how much
protection is necessary? In Elecraft's case, quite a lot, IMHO. With its QRP
DNA, Elecraft uses post crystal filter circuitry that minimizes current
consumption. The trade off for this is the need for a bank of pricey crystal
filters to limit the frequencies that the circuitry is exposed to.

Now what if the subsequent circuitry doesn't require this much protection
because it is more robust? We now have direct-sampling radios that can digitize
a whole ham band with good performance. If the BW was limited to 10-15 kHz in an
up conversion configuration they should be even better. The limitation now
becomes LO phase noise, but newer synthesizer designs overcome that obstacle.
Another thing to note is that IMD in crystal filters is reported to be inversely
proportional to BW. So a wider filter might actually be better from that
perspective. Some Elecraft filters exhibit passive IMD BTW.

Wes N7WS

On 6/14/2018 8:01 AM, WILLIE BABER wrote:

> Hello Wes,
>
> I took a look. Both designs are using the idea of "roofing filter" to refer to up-conversion radios similar to the use of up-conversion 3khz filters as roofing filters in Icom radios.
>
> "Roofing filter" (a mode specific filter after the first mixer including narrow cw filters) only makes sense in the context of the history of superhet design and in particular the use of one broad 15 khz first I-F (so that all modes may pass through it) typical of all Japanese radios until recently. Calling a 45 mhz filter at the first I-F a "roofing filter" as noted in the info you sent entirely misses the point of what roofing filter means. Or, to put it another way, all Ten-Tec radios had roofing filters in them (and were ssb and cw only) well before the term roofing filter was coined! Which is why an Omni C will out perform any wide (15 khz) first I-F Japanese radio, even those built well after the 1980 vintage Omni C.
>
> Unless mode specific up-conversion crystal filters can be made and as narrow as 200 hz (this is possible with down-conversion) then "roofing filter" and up conversion doesn't make sense historically or in reality.
>
> Actually, Icom says that did it with 1.2khz filter at 64 mhz in the Icom 7851, though I'm not convinced the filter is that narrow, and 1.2khz is far from the 200hz filter that my K3 has in it (however, the placement of this filter is why the 7851 is among the best radios in Sherwood's chart, on cw).
>
> It is possible to make very narrow and precise crystal filters as narrow as the 200 hz inexpensively, and this is the point of having multiple roofing filters at the first I-F. So, this is the origin of the term roofing filter---in comparison to the barn-door up conversion first I-F.
>
> 73, Will, wj9b
>
> CWops #1085
> CWA Advisor levels II and III
> http://cwops.org/
>
> --------------------------------------------
> On Wed, 6/13/18, Wes Stewart<[hidden email]> wrote:
>
> Subject: Re: [Elecraft] Field Day rig experience
> To:[hidden email]
> Date: Wednesday, June 13, 2018, 3:08 PM
>
> Certainly not to disparage the
> K3(S) architecture (I have two of them) there is
> nothing inherently wrong with an up-conversion
> receiver, if modern hardware is used.
>
> See:https://martein.home.xs4all.nl/pa3ake/hmode/g3sbi_intro.html
>
> and my friend Cornell's,
> Star-10 transceiver.
> https://pdfs.semanticscholar.org/eb33/5c12858779a653d9b9b93ca20120aebb7616.pdf
>
> Wes N7WS
>
>
> On 6/13/2018 11:38 AM, WILLIE BABER
> wrote:
> > Robert is talking about the
> crystal filters, also known as roofing filters now-days,
> that are typically placed after the first mixer (I
> mistakenly typed "ahead" but I meant
> "after" as Robert notes), though there is a post
> amp and NB before these filters in K2 and K3.
> >
> > The idea is that a
> crystal filter right after the first mixer gives high
> dynamic range because high selectivity comes before the
> receiver has developed stages of gain that otherwise could
> cause blocking or IMD, especially when selectivity is
> postponed to the second mixer while ignoring gain
> distribution in prior stages of the receiver. This basic
> idea was popularized in Solid State Design for the Radio
> Amateur, and it was applied to Ten-Tec radios for decades
> (at a 9 mhz I-F).
> >
> >
> Roofing filter gets defined in relationship to Japanese
> radios that had up conversion 15 khz filters at the first
> I-F, and generally lower dynamic range as a result, (but you
> got all modes, general coverage, and optional crystal
> filters at the second I-F).
> >
> > Good for everyone radios.... but with
> lower dynamic range and phase noise from the early
> synthesizers. This is why Ten-Tec radios were so popular
> among contesters, especially Omni V and VI (modified with a
> narrow cw filter at the first I-F).
> >
> > 73, Will, wj9b
> >
>
> ______________________________________________________________
> Elecraft mailing list
> Home:http://mailman.qth.net/mailman/listinfo/elecraft
> Help:http://mailman.qth.net/mmfaq.htm
> Post:mailto:[hidden email]
>
> This list hosted by:http://www.qsl.net
> Please help support this email list:http://www.qsl.net/donate.html
> Message delivered [hidden email]
> ______________________________________________________________
> Elecraft mailing list
> Home:http://mailman.qth.net/mailman/listinfo/elecraft
> Help:http://mailman.qth.net/mmfaq.htm
> Post:mailto:[hidden email]
>
> This list hosted by:http://www.qsl.net
> Please help support this email list:http://www.qsl.net/donate.html
> Message delivered [hidden email]

WILLIE BABER

Re: Field Day rig experience

In reply to this post by Bill-4

Wes,

"A "Roofing filter" is simply a filter in the radio's first IF through which all signals must pass before they will be "seen" by later receiver stages. The narrower this filter is, the less exposure later stages will have. Thus a "narrow" roofing filter is desirable -- but "narrow" is relative, as I'll explain."

What Elecraft said (above) is exactly what I said. Moreover, Elecraft's explanation is required because the term roofing filter is now applied to up-conversion in multiple conversion radios (with relatively wide first I-F filters compared to what is achievable at a low first I-F) which is what the term initially sought to rebuff in the first place, also my point.

73, Will, wj9b

CWops #1085
CWA Advisor levels II and III
http://cwops.org/

--------------------------------------------
On Thu, 6/14/18, Wes Stewart <[hidden email]> wrote:

Subject: Re: [Elecraft] Field Day rig experience
To: [hidden email]
Date: Thursday, June 14, 2018, 4:47 PM

Will,

First of all I have said before and will repeat
it, I detest the term "roofing
filter." That said, by the generally
accepted definition, you are wrong. See
Elecraft's take on this:

http://www.elecraft.com/K3/Roofing_Filters.htm

If you will think in
Wayne's terms, the post-mixer filter is a
"protective"
filter, not a
mode-specific filter. So the question becomes, how much

protection is necessary? In
Elecraft's case, quite a lot, IMHO. With its QRP
DNA, Elecraft uses post crystal filter
circuitry that minimizes current
consumption. The trade off for this is the
need for a bank of pricey crystal
filters
to limit the frequencies that the circuitry is exposed
to.

Now what if the
subsequent circuitry doesn't require this much
protection
because it is more robust? We
now have direct-sampling radios that can digitize
a whole ham band with good performance. If the
BW was limited to 10-15 kHz in an
up
conversion configuration they should be even better. The
limitation now
becomes LO phase noise, but
newer synthesizer designs overcome that obstacle.
Another thing to note is that IMD in crystal
filters is reported to be inversely
proportional to BW. So a wider filter might
actually be better from that
perspective.
Some Elecraft filters exhibit passive IMD BTW.

Wes N7WS

On 6/14/2018 8:01 AM, WILLIE BABER wrote:
> Hello Wes,
>
> I took a look. Both designs are using
the idea of "roofing filter" to refer to
up-conversion radios similar to the use of up-conversion
3khz filters as roofing filters in Icom radios.
>
> "Roofing
filter" (a mode specific filter after the first mixer
including narrow cw filters) only makes sense in the
context of the history of superhet design and in
particular the use of one broad 15 khz first I-F (so that
all modes may pass through it) typical of all Japanese
radios until recently. Calling a 45 mhz filter at the
first I-F a "roofing filter" as noted in the info
you sent entirely misses the point of what roofing filter
means. Or, to put it another way, all Ten-Tec radios had
roofing filters in them (and were ssb and cw only) well
before the term roofing filter was coined! Which is why an
Omni C will out perform any wide (15 khz) first I-F Japanese
radio, even those built well after the 1980 vintage Omni
C.
>
> Unless mode
specific up-conversion crystal filters can be made and as
narrow as 200 hz (this is possible with down-conversion)
then "roofing filter" and up conversion
doesn't make sense historically or in reality.
>
> Actually, Icom says
that did it with 1.2khz filter at 64 mhz in the Icom 7851,
though I'm not convinced the filter is that narrow, and
1.2khz is far from the 200hz filter that my K3 has in it
(however, the placement of this filter is why the 7851 is
among the best radios in Sherwood's chart, on cw).
>
> It is possible to
make very narrow and precise crystal filters as narrow as
the 200 hz inexpensively, and this is the point of having
multiple roofing filters at the first I-F. So, this is the
origin of the term roofing filter---in comparison to the
barn-door up conversion first I-F.
>
> 73, Will, wj9b
>
> CWops #1085
> CWA
Advisor levels II and III
> http://cwops.org/
>
>
--------------------------------------------
> On Wed, 6/13/18, Wes Stewart<[hidden email]>
wrote:
>
>   Subject:
Re: [Elecraft] Field Day rig experience
>   To:[hidden email]
>   Date: Wednesday, June 13, 2018, 3:08
PM
>
>
Certainly not to disparage the
>   K3(S)
architecture (I have two of them) there is
>   nothing inherently wrong with an
up-conversion
>   receiver, if modern
hardware is used.
>
>   See:https://martein.home.xs4all.nl/pa3ake/hmode/g3sbi_intro.html
>
>   and my friend
Cornell's,
>   Star-10
transceiver.
>   https://pdfs.semanticscholar.org/eb33/5c12858779a653d9b9b93ca20120aebb7616.pdf
>
>   Wes N7WS
>
>
> On 6/13/2018 11:38 AM, WILLIE
BABER
>   wrote:
>
> Robert is talking about the
>
crystal filters, also known as roofing filters now-days,
>   that are typically placed after the
first mixer (I
>   mistakenly typed
"ahead" but I meant
>
"after" as Robert notes), though there is a
post
>   amp and NB before these filters
in K2 and K3.
>   >
>   > The idea is that a
>   crystal filter right after the first
mixer gives high
>   dynamic range
because high selectivity comes before the
>   receiver has developed stages of gain
that otherwise could
>   cause blocking
or IMD, especially when selectivity is
>   postponed to the second mixer while
ignoring gain
>   distribution in prior
stages of the receiver. This basic
>
idea was popularized in Solid State Design for the Radio
>   Amateur, and it was applied to Ten-Tec
radios for decades
>   (at a 9 mhz
I-F).
>   >
>
>
>   Roofing filter gets defined in
relationship to Japanese
>   radios that
had up conversion 15 khz filters at the first
>   I-F, and generally lower dynamic range
as a result, (but you
>   got all modes,
general coverage, and optional crystal
>   filters at the second I-F).
>   >
>   > Good
for everyone radios.... but with
>
lower dynamic range and phase noise from the early
>   synthesizers. This is why Ten-Tec
radios were so popular
>   among
contesters, especially Omni V and VI (modified with a
>   narrow cw filter at the first I-F).
>   >
>   > 73,
Will, wj9b
>   >
>
>
______________________________________________________________
>   Elecraft mailing list
>   Home:http://mailman.qth.net/mailman/listinfo/elecraft
>   Help:http://mailman.qth.net/mmfaq.htm
>   Post:mailto:[hidden email]
>
>   This list
hosted by:http://www.qsl.net
>   Please help support this email list:http://www.qsl.net/donate.html
>   Message delivered [hidden email]
>
______________________________________________________________
> Elecraft mailing list
>
Home:http://mailman.qth.net/mailman/listinfo/elecraft
> Help:http://mailman.qth.net/mmfaq.htm
> Post:mailto:[hidden email]
>
> This list hosted
by:http://www.qsl.net
>
Please help support this email list:http://www.qsl.net/donate.html
> Message delivered [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

K9MA

Re: Field Day rig experience

There are at least two excellent reasons for the narrow crystal filters
in the first IF of the K3(s). (Wayne can correct me if I'm wrong.)
One, of course, is to reject the image of the second IF. However, the
dynamic range of the ADC in the second IF, by itself, just isn't enough
to provide the 140 or so dB we need. The combination of the ADC/DSP and
the crystal filter does the trick, even though 8 MHz crystal filters
aren't all that great. As I recall, there were some earlier DSP only
receivers, but their dynamic range was poor. Crystal filters are
expensive, but until we have fast ADC's linear to at least 24 bits,
they're necessary to get that kind of dynamic range.

I've often wondered if any other communication system requires the close
in dynamic range we do. Why would anyone design a system that allowed
signals 2 kHz apart to differ in strength by 140 dB?

73,
Scott K9MA

On 6/14/2018 20:33, WILLIE BABER wrote:

> Wes,
>
> "A "Roofing filter" is simply a filter in the radio's first IF through which all signals must pass before they will be "seen" by later receiver stages. The narrower this filter is, the less exposure later stages will have. Thus a "narrow" roofing filter is desirable -- but "narrow" is relative, as I'll explain."
>
> What Elecraft said (above) is exactly what I said. Moreover, Elecraft's explanation is required because the term roofing filter is now applied to up-conversion in multiple conversion radios (with relatively wide first I-F filters compared to what is achievable at a low first I-F) which is what the term initially sought to rebuff in the first place, also my point.
>
> 73, Will, wj9b
>
> CWops #1085
> CWA Advisor levels II and III
> http://cwops.org/
>
> --------------------------------------------
> On Thu, 6/14/18, Wes Stewart <[hidden email]> wrote:
>
> Subject: Re: [Elecraft] Field Day rig experience
> To: [hidden email]
> Date: Thursday, June 14, 2018, 4:47 PM
>
> Will,
>
> First of all I have said before and will repeat
> it, I detest the term "roofing
> filter." That said, by the generally
> accepted definition, you are wrong. See
> Elecraft's take on this:
>
> http://www.elecraft.com/K3/Roofing_Filters.htm
>
> If you will think in
> Wayne's terms, the post-mixer filter is a
> "protective"
> filter, not a
> mode-specific filter. So the question becomes, how much
>
> protection is necessary? In
> Elecraft's case, quite a lot, IMHO. With its QRP
> DNA, Elecraft uses post crystal filter
> circuitry that minimizes current
> consumption. The trade off for this is the
> need for a bank of pricey crystal
> filters
> to limit the frequencies that the circuitry is exposed
> to.
>
> Now what if the
> subsequent circuitry doesn't require this much
> protection
> because it is more robust? We
> now have direct-sampling radios that can digitize
> a whole ham band with good performance. If the
> BW was limited to 10-15 kHz in an
> up
> conversion configuration they should be even better. The
> limitation now
> becomes LO phase noise, but
> newer synthesizer designs overcome that obstacle.
> Another thing to note is that IMD in crystal
> filters is reported to be inversely
> proportional to BW. So a wider filter might
> actually be better from that
> perspective.
> Some Elecraft filters exhibit passive IMD BTW.
>
> Wes N7WS
>
> On 6/14/2018 8:01 AM, WILLIE BABER wrote:
> > Hello Wes,
> >
> > I took a look. Both designs are using
> the idea of "roofing filter" to refer to
> up-conversion radios similar to the use of up-conversion
> 3khz filters as roofing filters in Icom radios.
> >
> > "Roofing
> filter" (a mode specific filter after the first mixer
> including narrow cw filters) only makes sense in the
> context of the history of superhet design and in
> particular the use of one broad 15 khz first I-F (so that
> all modes may pass through it) typical of all Japanese
> radios until recently. Calling a 45 mhz filter at the
> first I-F a "roofing filter" as noted in the info
> you sent entirely misses the point of what roofing filter
> means. Or, to put it another way, all Ten-Tec radios had
> roofing filters in them (and were ssb and cw only) well
> before the term roofing filter was coined! Which is why an
> Omni C will out perform any wide (15 khz) first I-F Japanese
> radio, even those built well after the 1980 vintage Omni
> C.
> >
> > Unless mode
> specific up-conversion crystal filters can be made and as
> narrow as 200 hz (this is possible with down-conversion)
> then "roofing filter" and up conversion
> doesn't make sense historically or in reality.
> >
> > Actually, Icom says
> that did it with 1.2khz filter at 64 mhz in the Icom 7851,
> though I'm not convinced the filter is that narrow, and
> 1.2khz is far from the 200hz filter that my K3 has in it
> (however, the placement of this filter is why the 7851 is
> among the best radios in Sherwood's chart, on cw).
> >
> > It is possible to
> make very narrow and precise crystal filters as narrow as
> the 200 hz inexpensively, and this is the point of having
> multiple roofing filters at the first I-F. So, this is the
> origin of the term roofing filter---in comparison to the
> barn-door up conversion first I-F.
> >
> > 73, Will, wj9b
> >
> > CWops #1085
> > CWA
> Advisor levels II and III
> > http://cwops.org/
> >
> >
> --------------------------------------------
> > On Wed, 6/13/18, Wes Stewart<[hidden email]>
> wrote:
> >
> >   Subject:
> Re: [Elecraft] Field Day rig experience
> >   To:[hidden email]
> >   Date: Wednesday, June 13, 2018, 3:08
> PM
> >
> >
> Certainly not to disparage the
> >   K3(S)
> architecture (I have two of them) there is
> >   nothing inherently wrong with an
> up-conversion
> >   receiver, if modern
> hardware is used.
> >
> >   See:https://martein.home.xs4all.nl/pa3ake/hmode/g3sbi_intro.html
> >
> >   and my friend
> Cornell's,
> >   Star-10
> transceiver.
> >   https://pdfs.semanticscholar.org/eb33/5c12858779a653d9b9b93ca20120aebb7616.pdf
> >
> >   Wes N7WS
> >
> >
> > On 6/13/2018 11:38 AM, WILLIE
> BABER
> >   wrote:
> >
> > Robert is talking about the
> >
> crystal filters, also known as roofing filters now-days,
> >   that are typically placed after the
> first mixer (I
> >   mistakenly typed
> "ahead" but I meant
> >
> "after" as Robert notes), though there is a
> post
> >   amp and NB before these filters
> in K2 and K3.
> >   >
> >   > The idea is that a
> >   crystal filter right after the first
> mixer gives high
> >   dynamic range
> because high selectivity comes before the
> >   receiver has developed stages of gain
> that otherwise could
> >   cause blocking
> or IMD, especially when selectivity is
> >   postponed to the second mixer while
> ignoring gain
> >   distribution in prior
> stages of the receiver. This basic
> >
> idea was popularized in Solid State Design for the Radio
> >   Amateur, and it was applied to Ten-Tec
> radios for decades
> >   (at a 9 mhz
> I-F).
> >   >
> >
> >
> >   Roofing filter gets defined in
> relationship to Japanese
> >   radios that
> had up conversion 15 khz filters at the first
> >   I-F, and generally lower dynamic range
> as a result, (but you
> >   got all modes,
> general coverage, and optional crystal
> >   filters at the second I-F).
> >   >
> >   > Good
> for everyone radios.... but with
> >
> lower dynamic range and phase noise from the early
> >   synthesizers. This is why Ten-Tec
> radios were so popular
> >   among
> contesters, especially Omni V and VI (modified with a
> >   narrow cw filter at the first I-F).
> >   >
> >   > 73,
> Will, wj9b
> >   >
> >
> >
> ______________________________________________________________
> >   Elecraft mailing list
> >   Home:http://mailman.qth.net/mailman/listinfo/elecraft
> >   Help:http://mailman.qth.net/mmfaq.htm
> >   Post:mailto:[hidden email]
> >
> >   This list
> hosted by:http://www.qsl.net
> >   Please help support this email list:http://www.qsl.net/donate.html
> >   Message delivered [hidden email]
> >
> ______________________________________________________________
> > Elecraft mailing list
> >
> Home:http://mailman.qth.net/mailman/listinfo/elecraft
> > Help:http://mailman.qth.net/mmfaq.htm
> > Post:mailto:[hidden email]
> >
> > This list hosted
> by:http://www.qsl.net
> >
> Please help support this email list:http://www.qsl.net/donate.html
> > Message delivered [hidden email]
>
>
> ______________________________________________________________

--
Scott K9MA

[hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Wes Stewart-2

Re: Field Day rig experience

In reply to this post by WILLIE BABER

Okay, I'll give up, we'll just have to agree to disagree.

On 6/14/2018 6:33 PM, WILLIE BABER wrote:

WILLIE BABER

Re: Field Day rig experience

In reply to this post by Bill-4

Since it is meant for public consumption, maybe Wayne won't mind that I reproduce this, that Wes also cited (from the Elecraft website), written by Wayne, N6KR: Maybe we can agree that Wayne and Elecraft ought to know. And so end of thread.
-----------------------------------

What "Roofing Filter" means to Elecraft

There's been so much discussion about this topic that I'd thought I'd better try to clarify why we used the term when discussing the K3S.
A "Roofing filter" is simply a filter in the radio's first IF through which all signals must pass before they will be "seen" by later receiver stages. The narrower this filter is, the less exposure later stages will have. Thus a "narrow" roofing filter is desirable -- but "narrow" is relative, as I'll explain.

The term "roofing filter" has most often been used in relation to triple- or quadruple-conversion receivers. Such receivers have an IF above the highest RF band covered; it's typically something in the range of 30 to 70 MHz or higher. But "roofing" as a term should be interpreted as "protective," not "high in frequency." A roofing filter protects later stages, including amplifiers, mixers, narrower filters, and DSP subsystems, just as the roof on your house keeps rain out of all of the rooms. But a roofing filter can be equally at home at a low first IF, if that is how the radio is designed. It still provides the same protective function.

When we released the K2 in 1999, we never described our 1st IF crystal filters as roofing filters. We had only one IF, so the receiver model was simpler; there were no narrow filters at later stages that required protection.

But now, we find that the term is in widespread use. Average hams now think of roofing filter bandwidths as the standard of comparison between receivers. This is why manufacturers have jumped through hoops to try to provide the narrowest possible roofing filters. Many operators have an understanding (justified) that a roofing filter that is wider than the communications bandwidth will not best protect the receiver's later stages. So the term now seems appropriate to use even in a radio such as the K2, K3S, or Orion, all of which use low-frequency IFs (5 to 9 MHz).

In recent years, the roofing filter has become the centerpiece of receiver redesign:
Suppose that manufacturer "A" initially designed their receiver to use a 15- or 20-kHz roofing filter. Yes, this allows the receiver to handle NBFM and other wide modulation modes; it may also be selected to constrain the signal bandwidth ahead of a noise blanker or spectrum scope. But it comes at a price. If you're using CW mode, you'll have much narrower filters selected at the radio's 2nd and 3rd IFs. Yet the 1st IF roofing filter allows a broad swath of signals into the earlier stages. You don't need this energy in your passband. It can cause trouble.

Manufacturer "A," realizing they have a problem with dynamic range at close spacing, then announces that they've had a breakthrough: they can now offer a 6-kHz, or more recently 3-kHz roofing filter. This will certainly improve the situation for SSB and AM operation, but it still opens the barn door in CW or DATA modes, because the bandwidth is a factor of 10 wider than needed for communications.

So why don't they offer much narrower roofing filters that can be switched in for CW and data modes, or at times when adjacent-channel SSB QRM is very high? It's because they can't make filters any narrower at such a high IF.

Enter the "down-conversion" rig (K2, K3S, Orion, etc.). By converting to a low first IF, the designer can easily create narrow filters that are compatible with the required communications bandwidth. This is why we are offering filters with bandwidths as low as 200 Hz.

And yes, these are still "roofing" filters, because they limit exposure (bandwidth), thus protecting later stages (in the K3S case, the IF amp, 2nd mixer, and DSP).

73,
Wayne
N6KR

CWops #1085
CWA Advisor levels II and III
http://cwops.org/

--------------------------------------------
On Thu, 6/14/18, K9MA <[hidden email]> wrote:

Subject: Re: [Elecraft] Field Day rig experience
To: [hidden email]
Date: Thursday, June 14, 2018, 8:28 PM

There are at least two excellent
reasons for the narrow crystal filters
in
the first IF of the K3(s). (Wayne can correct me if
I'm wrong.)
One, of course, is to
reject the image of the second IF. However, the
dynamic range of the ADC in the second IF, by
itself, just isn't enough
to provide
the 140 or so dB we need. The combination of the ADC/DSP
and
the crystal filter does the trick, even
though 8 MHz crystal filters
aren't all
that great. As I recall, there were some earlier DSP only

receivers, but their dynamic range was
poor. Crystal filters are
expensive, but
until we have fast ADC's linear to at least 24 bits,
they're necessary to get that kind of
dynamic range.

I've
often wondered if any other communication system requires
the close
in dynamic range we do. Why
would anyone design a system that allowed
signals 2 kHz apart to differ in strength by
140 dB?

73,
Scott K9MA

On 6/14/2018
20:33, WILLIE BABER wrote:
> Wes,
>
> "A "Roofing
filter" is simply a filter in the radio's first IF
through which all signals must pass before they will be
"seen" by later receiver stages. The narrower this
filter is, the less exposure later stages will have. Thus a
"narrow" roofing filter is desirable -- but
"narrow" is relative, as I'll
explain."
>
>
What Elecraft said (above) is exactly what I said.
Moreover, Elecraft's explanation is required because the
term roofing filter is now applied to up-conversion in
multiple conversion radios (with relatively wide first I-F
filters compared to what is achievable at a low first I-F)
which is what the term initially sought to rebuff in the
first place, also my point.
>
> 73, Will, wj9b
>
> CWops #1085
> CWA
Advisor levels II and III
> http://cwops.org/
>
>
--------------------------------------------
> On Thu, 6/14/18, Wes Stewart <[hidden email]>
wrote:
>
>   Subject:
Re: [Elecraft] Field Day rig experience
>   To: [hidden email]
>   Date: Thursday, June 14, 2018, 4:47
PM
>
>   Will,
>
>   First of all I
have said before and will repeat
>   it,
I detest the term "roofing
>
filter." That said, by the generally
>   accepted definition, you are wrong.
See
>   Elecraft's take on this:
>
>   http://www.elecraft.com/K3/Roofing_Filters.htm
>
>   If you will
think in
>   Wayne's terms, the
post-mixer filter is a
>
"protective"
>   filter, not
a
>   mode-specific filter. So the
question becomes, how much
>
>   protection is necessary? In
>   Elecraft's case, quite a lot,
IMHO. With its QRP
>   DNA, Elecraft
uses post crystal filter
>   circuitry
that minimizes current
>
consumption. The trade off for this is the
>   need for a bank of pricey crystal
>   filters
>   to
limit the frequencies that the circuitry is exposed
>   to.
>
>   Now what if the
>
subsequent circuitry doesn't require this much
>   protection
>
because it is more robust? We
>   now
have direct-sampling radios that can digitize
>   a whole ham band with good performance.
If the
>   BW was limited to 10-15 kHz
in an
>   up
>
conversion configuration they should be even better.
The
>   limitation now
>   becomes LO phase noise, but
>   newer synthesizer designs overcome that
obstacle.
>   Another thing to note is
that IMD in crystal
>   filters is
reported to be inversely
>
proportional to BW. So a wider filter might
>   actually be better from that
>   perspective.
>
Some Elecraft filters exhibit passive IMD BTW.
>
>   Wes N7WS
>
>   On 6/14/2018
8:01 AM, WILLIE BABER wrote:
>   >
Hello Wes,
>   >
>   > I took a look. Both designs are
using
>   the idea of "roofing
filter" to refer to
>
up-conversion radios similar to the use of up-conversion
>   3khz filters as roofing filters in Icom
radios.
>   >
>
> "Roofing
>   filter" (a
mode specific filter after the first mixer
>   including narrow cw filters) only makes
sense in the
>   context of the
history of superhet design and in
>
particular the use of one broad 15 khz first I-F (so that
>   all modes may pass through it) typical
of all Japanese
>   radios until
recently. Calling a 45 mhz filter at the
>   first I-F a "roofing filter"
as noted in the info
>   you sent
entirely misses the point of what roofing filter
>   means. Or, to put it another way, all
Ten-Tec radios had
>   roofing filters
in them (and were ssb and cw only) well
>   before the term roofing filter was
coined! Which is why an
>   Omni C
will out perform any wide (15 khz) first I-F Japanese
>   radio, even those built well after the
1980 vintage Omni
>   C.
>   >
>   >
Unless mode
>   specific up-conversion
crystal filters can be made and as
>
narrow as 200 hz (this is possible with down-conversion)
>   then "roofing filter" and up
conversion
>   doesn't make sense
historically or in reality.
>   >
>   > Actually, Icom says
>   that did it with 1.2khz filter at 64
mhz in the Icom 7851,
>   though I'm
not convinced the filter is that narrow, and
>   1.2khz is far from the 200hz filter
that my K3 has in it
>   (however, the
placement of this filter is why the 7851 is
>   among the best radios in Sherwood's
chart, on cw).
>   >
>   > It is possible to
>   make very narrow and precise crystal
filters as narrow as
>   the 200 hz
inexpensively, and this is the point of having
>   multiple roofing filters at the first
I-F. So, this is the
>   origin of the
term roofing filter---in comparison to the
>   barn-door up conversion first I-F.
>   >
>   > 73,
Will, wj9b
>   >
>   > CWops #1085
>
> CWA
>   Advisor levels II and
III
>   > http://cwops.org/
>
>
>   >
>
--------------------------------------------
>   > On Wed, 6/13/18, Wes Stewart<[hidden email]>
>   wrote:
>   >
>   >   Subject:
>   Re: [Elecraft] Field Day rig
experience
>   >   To:[hidden email]
>   >   Date: Wednesday, June 13,
2018, 3:08
>   PM
>
>
>   >
>
Certainly not to disparage the
>
>   K3(S)
>   architecture (I have
two of them) there is
>   >
nothing inherently wrong with an
>
up-conversion
>   >   receiver, if
modern
>   hardware is used.
>   >
>   >
See:https://martein.home.xs4all.nl/pa3ake/hmode/g3sbi_intro.html
>   >
>   >
and my friend
>   Cornell's,
>   >   Star-10
>
transceiver.
>   >   https://pdfs.semanticscholar.org/eb33/5c12858779a653d9b9b93ca20120aebb7616.pdf
>   >
>   >
Wes N7WS
>   >
>   >
>   >
  On 6/13/2018 11:38 AM, WILLIE
>
BABER
>   >   wrote:
>   >
>   >
Robert is talking about the
>   >
>   crystal filters, also known as roofing
filters now-days,
>   >   that are
typically placed after the
>   first
mixer (I
>   >   mistakenly
typed
>   "ahead" but I
meant
>   >
>
"after" as Robert notes), though there is a
>   post
>   >
amp and NB before these filters
>   in
K2 and K3.
>   >   >
>   >   > The idea is that a
>   >   crystal filter right after the
first
>   mixer gives high
>   >   dynamic range
>   because high selectivity comes before
the
>   >   receiver has developed
stages of gain
>   that otherwise
could
>   >   cause blocking
>   or IMD, especially when selectivity
is
>   >   postponed to the second
mixer while
>   ignoring gain
>   >   distribution in prior
>   stages of the receiver. This basic
>   >
>   idea was
popularized in Solid State Design for the Radio
>   >   Amateur, and it was applied to
Ten-Tec
>   radios for decades
>   >   (at a 9 mhz
>   I-F).
>   >
>
>   >
>
>
>   >   Roofing filter gets
defined in
>   relationship to
Japanese
>   >   radios that
>   had up conversion 15 khz filters at the
first
>   >   I-F, and generally
lower dynamic range
>   as a result,
(but you
>   >   got all modes,
>   general coverage, and optional
crystal
>   >   filters at the
second I-F).
>   >   >
>   >   > Good
>   for everyone radios.... but with
>   >
>   lower
dynamic range and phase noise from the early
>   >   synthesizers. This is why
Ten-Tec
>   radios were so popular
>   >   among
>
contesters, especially Omni V and VI (modified with a
>   >   narrow cw filter at the first
I-F).
>   >   >
>   >   > 73,
>   Will, wj9b
>
>   >
>   >
>   >
>
______________________________________________________________
>   >   Elecraft mailing list
>   >   Home:http://mailman.qth.net/mailman/listinfo/elecraft
>   >   Help:http://mailman.qth.net/mmfaq.htm
>   >   Post:mailto:[hidden email]
>   >
>   >
This list
>   hosted by:http://www.qsl.net
>   >   Please help support this email
list:http://www.qsl.net/donate.html
>   >   Message delivered [hidden email]
>   >
>
______________________________________________________________
>   > Elecraft mailing list
>   >
>   Home:http://mailman.qth.net/mailman/listinfo/elecraft
>   > Help:http://mailman.qth.net/mmfaq.htm
>   > Post:mailto:[hidden email]
>   >
>   > This
list hosted
>   by:http://www.qsl.net
>   >
>   Please
help support this email list:http://www.qsl.net/donate.html
>   > Message delivered [hidden email]
>
>
>
______________________________________________________________

--
Scott K9MA

[hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]