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K3: FM Filter for AM?

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Bill Henderson

K3: FM Filter for AM?

Hi

I already have the 250Hz, 400Hz and 2.7 KHz filters fitted to both receivers. I plan to add 2.1KHz or 1.8kHz filters some time I in the future.

In the nearer future I intend adding the 2m module to my K3. Since this will be used for local traffic I understand that I need to add an FM filter on the main receiver. Since this is a wide filter can I use it for AM as well? If not then I would “need” 6 filters with only 5 slots available.

I am a black box operator. If I find more than one switch on that box I burst into tears. So please bear this in mind in your answers.

Tia

Bill
GM0VIT

Don Wilhelm-4

Re: K3: FM Filter for AM?

Bill,

You can use the FM filter to receive AM, but not for transmit. To
transmit AM, you must have the 6 kHz filter, so you will have to
sacrifice one filter.

73,
Don W3FPR

On 10/8/2010 9:11 AM, Bill Henderson wrote:

> Hi
>
> I already have the 250Hz, 400Hz and 2.7 KHz filters fitted to both
> receivers. I plan to add 2.1KHz or 1.8kHz filters some time I in the future.
>
> In the nearer future I intend adding the 2m module to my K3. Since this will
> be used for local traffic I understand that I need to add an FM filter on
> the main receiver. Since this is a wide filter can I use it for AM as well?
> If not then I would “need” 6 filters with only 5 slots available.
>
> I am a black box operator. If I find more than one switch on that box I
> burst into tears. So please bear this in mind in your answers.
>
> Tia
>
> Bill
> GM0VIT
>

Bill Henderson

Re: K3: FM Filter for AM?

Don

I thought that that might be the case.

I can live without TX in AM (hi)

Vy 73

Bill

Joe Subich, W4TV-4

Re: K3: FM Filter for AM?

In reply to this post by Don Wilhelm-4

On 10/8/2010 9:30 AM, Don Wilhelm wrote:
>
> You can use the FM filter to receive AM, but not for transmit. To
> transmit AM, you must have the 6 kHz filter, so you will have to
> sacrifice one filter.

Repeating one of my complaints about the K3 .... there is no reason
that the FM filter should not be usable for AM (or ESSB) transmit.
The filter response is well into its stopband for the IF image. I've
checked both of my K3s on a spectrum analyzer (by telling the K3 the
FM filter was 6 KHz wide) and there is no measurable/detectable
transmit image.

73,

... Joe, W4TV

On 10/8/2010 9:30 AM, Don Wilhelm wrote:

> Bill,
>
> You can use the FM filter to receive AM, but not for transmit. To
> transmit AM, you must have the 6 kHz filter, so you will have to
> sacrifice one filter.
>
> 73,
> Don W3FPR
>
> On 10/8/2010 9:11 AM, Bill Henderson wrote:
>> Hi
>>
>> I already have the 250Hz, 400Hz and 2.7 KHz filters fitted to both
>> receivers. I plan to add 2.1KHz or 1.8kHz filters some time I in the future.
>>
>> In the nearer future I intend adding the 2m module to my K3. Since this will
>> be used for local traffic I understand that I need to add an FM filter on
>> the main receiver. Since this is a wide filter can I use it for AM as well?
>> If not then I would “need” 6 filters with only 5 slots available.
>>
>> I am a black box operator. If I find more than one switch on that box I
>> burst into tears. So please bear this in mind in your answers.
>>
>> Tia
>>
>> Bill
>> GM0VIT
>>
> ______________________________________________________________
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Bob Naumann W5OV

Re: K3: FM Filter for AM?

Can someone explain why this restriction exists?

*Why* can't you transmit through a 2.1 filter for example. *Why* is it
precluded?

I don't want a 2.7 or a 2.8 filter tying up one of the too few filter slots.

W5OV

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Joe Subich, W4TV
Sent: Friday, October 08, 2010 11:07 AM
To: [hidden email]
Subject: Re: [Elecraft] K3: FM Filter for AM?

On 10/8/2010 9:30 AM, Don Wilhelm wrote:
>
> You can use the FM filter to receive AM, but not for transmit. To
> transmit AM, you must have the 6 kHz filter, so you will have to
> sacrifice one filter.

Repeating one of my complaints about the K3 .... there is no reason
that the FM filter should not be usable for AM (or ESSB) transmit.
The filter response is well into its stopband for the IF image. I've
checked both of my K3s on a spectrum analyzer (by telling the K3 the
FM filter was 6 KHz wide) and there is no measurable/detectable
transmit image.

73,

... Joe, W4TV

On 10/8/2010 9:30 AM, Don Wilhelm wrote:

future.
>>
>> In the nearer future I intend adding the 2m module to my K3. Since this
will
>> be used for local traffic I understand that I need to add an FM filter on
>> the main receiver. Since this is a wide filter can I use it for AM as
well?

>> If not then I would "need" 6 filters with only 5 slots available.
>>
>> I am a black box operator. If I find more than one switch on that box I
>> burst into tears. So please bear this in mind in your answers.
>>
>> Tia
>>
>> Bill
>> GM0VIT
>>
> ______________________________________________________________
> Elecraft mailing list
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Don Cunningham

Re: K3: FM Filter for AM?

I agree, Bob, and wouldn't 2.1 kc make our transmit signal even cleaner??
I'm afraid I don't see the "status quo" either.
73,
Don, WB5HAK

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Doug Faunt N6TQS +1-510-655-8604

Re: K3: FM Filter for AM?

In fact, 2.1 was one of the original possibilities for the TX filter
and was removed.
73, doug

From: "Don Cunningham" <[hidden email]>
Date: Fri, 8 Oct 2010 11:31:04 -0500

I agree, Bob, and wouldn't 2.1 kc make our transmit signal even cleaner??
I'm afraid I don't see the "status quo" either.
73,
Don, WB5HAK
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wayne burdick

Re: FM Filter for AM?

Administrator

In reply to this post by Bob Naumann W5OV

Bob,

I could change all of the transmit filter bandwidth restrictions in
firmware, and this is on my list. But it would be a complex change,
and I have to weigh it against many competing firmware change
requests. I assume the presence of a 2.7 or 2.8 kHz filter in all of
the frequency-setting algorithms for SSB, CW, and DATA modes.
Similarly, I assume a 6 kHz filter for TX in AM and ESSB modes.

73,
Wayne
N6KR

Bob Naumann wrote:

> Can someone explain why this restriction exists?
>
> *Why* can't you transmit through a 2.1 filter for example. *Why* is it
> precluded?

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Don Cunningham

Re: FM Filter for AM?

Wayne,
Would you mind answering the question of transmit purity. Would the change
from 2.8 to 2.1 make our transmissions any "cleaner"?? If not, it would not
be worth all the work you would need to do. Thanks to listening to our
"requests". That is what makes Elecraft so good, other manufacturers turn a
deaf ear.
73,
Don, WB5HAK

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Jan Erik Holm

Re: FM Filter for AM?

In reply to this post by wayne burdick

Yes please do!!

Jim
--------
On 2010-10-08 18:56, Wayne Burdick wrote:

> Bob,
>
> I could change all of the transmit filter bandwidth restrictions in
> firmware, and this is on my list. But it would be a complex change,
> and I have to weigh it against many competing firmware change
> requests. I assume the presence of a 2.7 or 2.8 kHz filter in all of
> the frequency-setting algorithms for SSB, CW, and DATA modes.
> Similarly, I assume a 6 kHz filter for TX in AM and ESSB modes.
>
> 73,
> Wayne
> N6KR
>
> Bob Naumann wrote:
>
>> Can someone explain why this restriction exists?
>>
>> *Why* can't you transmit through a 2.1 filter for example. *Why* is it
>> precluded?
>

Ken Kopp-3

FM Filter for AM?

If this change is made, we should be prepared for
complaints about Elecraft transmitters being "wide",
"splattering", etc. The present filter imitations serve
to protect some of us from both unintended and intentional
excessive bandwidth.

Elecraft's excellent reputation for "clean" transmitters will
likely be tarnished.

73! Ken Kopp - K0PP
[hidden email]

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Joe Subich, W4TV-4

Re: FM Filter for AM?

> The present filter imitations serve to protect some of us
> from both unintended and intentional excessive bandwidth.

AM/ESSB/SSB bandwidth is determined by the DSP modulation
not the roofing filter bandwidth. This can easily be seen
in the use of the 6 KHz filter for ESSB where the occupied
bandwidth (3.0 - 4.0 KHz) options are significantly less
than the -6 dB bandwidth of the AM filter.

In any case, even the tightest filter will not prevent
"wide" signals caused by over driving the final amplifier
since the filtering occurs well before the amplifier.

Quite simply, the only time the SSB filter controls the
bandwidth is with analog SSB generation using the filter
method. With both AM and SSB generated by either the
phasing method or using DSP techniques, the bandwidth is
determined by the bandwidth of the audio input (that is,
the highest modulating frequency.

73,

... Joe, W4TV

On 10/8/2010 1:58 PM, Ken Kopp wrote:

>
> If this change is made, we should be prepared for
> complaints about Elecraft transmitters being "wide",
> "splattering", etc. The present filter imitations serve
> to protect some of us from both unintended and intentional
> excessive bandwidth.
>
> Elecraft's excellent reputation for "clean" transmitters will
> likely be tarnished.
>
> 73! Ken Kopp - K0PP
> [hidden email]
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
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>

Joe Subich, W4TV-4

Re: FM Filter for AM?

In reply to this post by wayne burdick

> Similarly, I assume a 6 kHz filter for TX in AM and ESSB modes.

That's a problematic assumption. If one has 2.7 or 2.8 plus a
narrow SSB filter (1.5/1.8) a normal CW/RTTY filter and a narrow
CW filter there is simply no way to support both FM (4.5 KHz DSB
AM RX) and normal AM filters. Since the combination of the FM
filter and DSP is more than satisfactory for reduced bandwidth
AM, the FM filter should be supported for AM/ESSB transmit when
the available filter slots are otherwise occupied.

73,

... Joe, W4TV

On 10/8/2010 12:56 PM, Wayne Burdick wrote:

> Bob,
>
> I could change all of the transmit filter bandwidth restrictions in
> firmware, and this is on my list. But it would be a complex change, and
> I have to weigh it against many competing firmware change requests. I
> assume the presence of a 2.7 or 2.8 kHz filter in all of the
> frequency-setting algorithms for SSB, CW, and DATA modes. Similarly, I
> assume a 6 kHz filter for TX in AM and ESSB modes.
>
> 73,
> Wayne
> N6KR
>
> Bob Naumann wrote:
>
>> Can someone explain why this restriction exists?
>>
>> *Why* can't you transmit through a 2.1 filter for example. *Why* is it
>> precluded?
>
>
>
>

Ken Kopp-3

Re: FM Filter for AM?

In reply to this post by Joe Subich, W4TV-4

Thanks for clarifying the maximum achievable
transmitted bandwidth issue, Joe. I was aware
of this, but it had retreated to the nether regions
of my old poop's brain. (;-)

73! Ken Kopp - K0PP

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Guy, K2AV

Re: K3: FM Filter for AM?

In reply to this post by Doug Faunt N6TQS +1-510-655-8604

You will have to choose which filter is used ALL THE TIME for SSB TX.

You COULD currently define the 2.1 filter as 2.7 and set an offset to
center it properly. BUT it will not be cleaner as you suppose. The
narrower filters have more envelope delay near the skirts, and that
creates distortion and widened bandwidth. You will have distortion
products that are outside the filter bandwidth. You should also note,
that the choice to transmit CW through the 2.7/2.8 filter was at least
partly made with a CLEANER signal in mind by not adding distortion.

The K3 is NOT an analog radio.

The CW signal is not made by turning an oscillator on and off,
modulated by the rise time of a controlling voltage. It is a stream
of numbers which describes a pristine CW signal. For ALL transmitted
output, the DSP drives an analog to digital converter whose output is
the TX IF signal which is upconverted and amplified exactly the same
way for all TX output. There is no balanced modulator to create the
SSB signal. After d/a conversion, only SSB style high linearity keeps
a signal pristine. Envelope delay in narrower filters will BROADEN
the CW envelope, not narrow it. A CW signal generated in the K3
fashion cannot be narrowed except in the firmware. The rise time
option picks between number streams used as input to the DAC, not
between timing capacitors in an analog on/off circuit.

Transmitting a clean signal at a legal bandwidth is FAR more
complicated than where the skirts are. It is a different issue to use
an FM roofing filter to pass AM bandwidth transmitting, but there is
still the issue of legal bandwidth for an emission and the K3 needing
to maintain type acceptance. Strictly speaking, Elecraft may not
publish methods, assist, provide advice, parts or software which make
it possible for a type accepted rig to operate outside the type
restrictions and legal modes in the countries involved.

Users on the Elecraft repeater may bemoan not being able to do this or
that, but the hard deck is that Wayne has to follow the rules or lose
type acceptance. 10 kHz ESSB is not legal on HF, and Wayne can't
provide the means to allow a K3 to do so. Much of his means to keep
things legal is also embedded in proprietary code. Also, trying to
get him to lay it all out so we can feel "happy" about being
restricted to FCC regs, is asking him to lay out his "stuff" which
then can be copied by competitors.

This ain't your daddy's analog radio. Like there is no RF gain in a
K3. The only reason there is a knob called RF gain was the marketing
determination that it would not be accepted unless it quacked, walked
and swam like an analog radio, and had all the same knobs. I am sure
that TenTec's experience with this in the Orion series was known when
the decisions were being made. The knob controls variable IF gain.
But the pot is not in the RF/IF string. It's followed by an analog to
digital converter that converts the pot position to a number and sends
the number on to the MPU. RF gain can be "chunk adjusted" by turning
preamp/ATT on and off.

So the K3 knobs and twiddles LIKE an analog radio, with an analog
face, but only a skin deep resemblance. The key to understanding the
K3 is shedding the old analog understandings in favor of learning the
digital innards of the K3. Learning to read the K3 schematics and
spending some time in them is useful. I realize that's a bit worse
than RTFM, but it does get you out of the mode of thinking of the K3
as a series of individual digital emulations of individual analog tube
circuits.

Just how the firmware deals with the digital equivalent of "AGC off"
is another story. I think that AGC off should just be an extreme
setting of AGC on, where LIM sets the loudest audio you want to hear
in any mode any setting.

73, Guy.

On Fri, Oct 8, 2010 at 12:39 PM, Doug Faunt N6TQS +1-510-655-8604
<[hidden email]> wrote:

> In fact, 2.1 was one of the original possibilities for the TX filter
> and was removed.
> 73, doug
>
>
> From: "Don Cunningham" <[hidden email]>
> Date: Fri, 8 Oct 2010 11:31:04 -0500
>
> I agree, Bob, and wouldn't 2.1 kc make our transmit signal even cleaner??
> I'm afraid I don't see the "status quo" either.
> 73,
> Don, WB5HAK
> ______________________________________________________________
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> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>

Bob Naumann W5OV

Re: FM Filter for AM?

In reply to this post by wayne burdick

Wayne,

Am I correct in my understanding that the reason the 2.1 is not currently
allowed is simply a firmware issue?

If it is indeed technically OK to use the 2.1 instead of the 2.7 or 2.8, yes
- I would like that option to be available.

I was surprised that after removing the 2.7 and installing the 2.1 that its
selection as a transmit filter was precluded.

The 2.1 is much better than the 2.7 for SSB reception, and if it is OK to
transmit through, I would not need to waste a filter slot on the 2.7.

73,

Bob W5OV

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Wayne Burdick
Sent: Friday, October 08, 2010 11:56 AM
To: Bob Naumann
Cc: [hidden email]
Subject: Re: [Elecraft] FM Filter for AM?

Bob,

I could change all of the transmit filter bandwidth restrictions in
firmware, and this is on my list. But it would be a complex change,
and I have to weigh it against many competing firmware change
requests. I assume the presence of a 2.7 or 2.8 kHz filter in all of
the frequency-setting algorithms for SSB, CW, and DATA modes.
Similarly, I assume a 6 kHz filter for TX in AM and ESSB modes.

73,
Wayne
N6KR

Bob Naumann wrote:

> Can someone explain why this restriction exists?
>
> *Why* can't you transmit through a 2.1 filter for example. *Why* is it
> precluded?

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wayne burdick

Re: FM Filter for AM?

Administrator

Bob Naumann wrote:

> Wayne,
>
> Am I correct in my understanding that the reason the 2.1 is not
> currently
> allowed is simply a firmware issue?

Yes. As usual we have a long list of customer requests that we're
working on. This is one of them (along with allowing the FM filter to
be used for AM TX).

> I was surprised that after removing the 2.7 and installing the 2.1
> that its
> selection as a transmit filter was precluded.

I believe the owner's manual and assembly manual both state that you
need either a 2.7 or 2.8 kHz filter installed. But we many need to
further clarify this.

73,
Wayne
N6KR

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Bob Naumann W5OV

Re: FM Filter for AM?

Thanks Wayne for this information.

To be honest, I did not look at the manual for restrictions on what filter
could be used as I didn't expect there to be any restrictions - especially
for SSB.

So, from a technical standpoint, my expectations were correct, it's just
that the firmware does not yet allow what I presumed would be completely up
to the end user to decide.

I look forward to this coming to the top of the lengthening request list.

Thanks again & 73,

Bob W5OV

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Wayne Burdick
Sent: Saturday, October 09, 2010 9:54 AM
To: Bob Naumann
Cc: [hidden email]
Subject: Re: [Elecraft] FM Filter for AM?

Bob Naumann wrote:

> Wayne,
>
> Am I correct in my understanding that the reason the 2.1 is not
> currently
> allowed is simply a firmware issue?

Yes. As usual we have a long list of customer requests that we're
working on. This is one of them (along with allowing the FM filter to
be used for AM TX).

> I was surprised that after removing the 2.7 and installing the 2.1
> that its
> selection as a transmit filter was precluded.

I believe the owner's manual and assembly manual both state that you
need either a 2.7 or 2.8 kHz filter installed. But we many need to
further clarify this.

73,
Wayne
N6KR

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Bill Henderson

Re: FM Filter for AM?

Hi

Does this mean that I should not worry about the AM filter in the certain knowledge that I will, sooner or later, be able to transmit AM using the FM filter?

If so let me chance my arm by asking how far away this change is (Hi).

73

Bill

Doug Alspaugh

Re: FM Filter for AM?

In reply to this post by wayne burdick

--------------------------------------------------
From: "Wayne Burdick" <[hidden email]>
Sent: Saturday, October 09, 2010 10:54 AM
To: "Bob Naumann" <[hidden email]>
Cc: <[hidden email]>
Subject: Re: [Elecraft] FM Filter for AM?

> Bob Naumann wrote:
>
>> Wayne,
>>
>> Am I correct in my understanding that the reason the 2.1 is not
>> currently
>> allowed is simply a firmware issue?
>
> Yes. As usual we have a long list of customer requests that we're
> working on.

OOOOOOO OOOOOOO Yeeeeeeeeeeeeeeeeeeess

>>>>> This is one of them (along with allowing the FM filter to
>>>>> be used for AM TX).

>
>
>> I was surprised that after removing the 2.7 and installing the 2.1
>> that its
>> selection as a transmit filter was precluded.
>
> I believe the owner's manual and assembly manual both state that you
> need either a 2.7 or 2.8 kHz filter installed. But we many need to
> further clarify this.
>
> 73,
> Wayne
> N6KR
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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