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K3: SSB - WPX - Filters - Controls

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k0wa@swbell.net

K3: SSB - WPX - Filters - Controls

I would like to make a few comments and ask some questions. This is by no means a put-down of the the K3, because I am not sure I am operating the rig correctly. After all it is a SDR and it is new.

During my first foray into SSB Contesting with the K3 during WPX, I found that I need either:

1. Understand more about the DSP and the controls for BW, Hcut and Lcut

2. Obtain a narrower roofing filter for SSB - like a 1.8 Khz filter

3. Or both.

I spent some time trying to find the sweet spot in the radio for SSB using the 2.8 Khz filter. I don't think I found it. At least, I am not satisfied.

I tried narrowing up the filter bandwidth to 2.4 or 2.2....some times 1.8.
I tried shifting it up and down the bandpass.
I tried to use High Cut and Low Cut depending on where the offending signal was coming from.
AGC was on Slow with the standard settings.
Used the RIT a lot

It seemed I was always fighting some sort of side band splatter or stations close in on the frequency. Maybe it was just a crowded 20 meter band, but the same things happened on 40 meters.

Do I need to go to a 1.8 Khz filter to give the DSP a break?
Do I need to understand and play with the RX more to make sure I am doing it right.

I would like to some feedback and comments on how other people set up their K3s for SSB contesting.

I want to learn more about this radio.

Lee - K0WA

In our day and age it seems that Common Sense is in short supply. If you don't have any Common Sense - get some Common Sense and use it. If you can't find any Common Sense, ask for help from somebody who has some Common Sense. Is Common Sense divine?
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mark roz

Re: K3: SSB - WPX - Filters - Controls

I have made 700 QSO's in WPX SSB contest(part time). I have also tried different adjustment on the K3 including RX EQ.

I have to say the same thing "It seemed I was always fighting some sort of side band splatter or stations close in on the frequency".

Splatter is always in the contest but not as pronounced as with K3.
I don't know if it is the freq. response or something else with DSP.
I was so tired after few hundred QSO's. I have switched to TS930S.
With TS930s it was much better. Signals were much cleaner more dynamic
and the splatter not as offending as with K3.
I have 2.7kHz filter in my K3.

I like K3 very much in CW CONTEST but don't like in SSB contest at all.

Also, for some reason the output power from the K3 was fluctuating in time.
I had to keep adjusting PWR. My alpha 87A was showing 1500W PEP and than about 900W and so on. Than after 10 second or so again 1500W.
Looked to me like ALC action in the K3 was not always the same. I don't connect ALC to the amp. Same thing when I switched to IC-4KL amp.

Mark

--- On Mon, 3/31/08, Lee Buller <[hidden email]> wrote:

> From: Lee Buller <[hidden email]>
> Subject: [Elecraft] K3: SSB - WPX - Filters - Controls
> To: "Elecraft Reflector" <[hidden email]>
> Date: Monday, March 31, 2008, 6:31 AM
> I would like to make a few comments and ask some questions.
> This is by no means a put-down of the the K3, because I am
> not sure I am operating the rig correctly. After all it is
> a SDR and it is new.
>
> During my first foray into SSB Contesting with the K3
> during WPX, I found that I need either:
>
> 1. Understand more about the DSP and the controls for BW,
> Hcut and Lcut
>
> 2. Obtain a narrower roofing filter for SSB - like a 1.8
> Khz filter
>
> 3. Or both.
>
> I spent some time trying to find the sweet spot in the
> radio for SSB using the 2.8 Khz filter. I don't think
> I found it. At least, I am not satisfied.
>
> I tried narrowing up the filter bandwidth to 2.4 or
> 2.2....some times 1.8.
> I tried shifting it up and down the bandpass.
> I tried to use High Cut and Low Cut depending on where the
> offending signal was coming from.
> AGC was on Slow with the standard settings.
> Used the RIT a lot
>
> It seemed I was always fighting some sort of side band
> splatter or stations close in on the frequency. Maybe it
> was just a crowded 20 meter band, but the same things
> happened on 40 meters.
>
> Do I need to go to a 1.8 Khz filter to give the DSP a
> break?
> Do I need to understand and play with the RX more to make
> sure I am doing it right.
>
> I would like to some feedback and comments on how other
> people set up their K3s for SSB contesting.
>
> I want to learn more about this radio.
>
> Lee - K0WA
>
>
>
>
>
>
> In our day and age it seems that Common Sense is in short
> supply. If you don't have any Common Sense - get some
> Common Sense and use it. If you can't find any Common
> Sense, ask for help from somebody who has some Common
> Sense. Is Common Sense divine?
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

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Bjorn

Re: K3: SSB - WPX - Filters - Controls

In reply to this post by k0wa@swbell.net

Lee,

The WPX contest was an interesting experience with the K3. I was working 670
contacts in single op all band non assisted high pwr mode. I am not a very
experienced contester, but I have been working a number of SSB contests with
my MP over the past 2-3 years.

My impression of the K3 is similar to what you and Mark Roz describe. First
I thought it was the headphones but soon I realized that the radio sounds a
little different that I am used to. Some high pitched audio appeared very
sharp, and less filtered than I am used to and splatter was hard to fight.

I was normally starting with a 2.4 kc bandwidth, working my way down below 2
kc when there was a lot of splatter. I also noticed that I had to center the
passband very low in most cases to dig out the signal. That seemed a little
different depending on the spectrum energy in the received signal, but most
often my passband was tuned very low for best receive. After the WPX
experience I am now willing to try a sharper SSB filer, I think it is
needed.

I also tried noise reduction as higher bands sometimes where very noisy and
signals weak. For me, DSP NR never really worked well. The NR in the K3
seems to do a pretty nice job, but still my brain is far better.

I have also noticed the fluctuation in output, not being sure if it was my
low band antennas rocking in the wind or something else. I read Sunday about
some SSB issues in the current firmware release, so they might be dealt with
soon. Unfortunately I updated my firmware right before the contest.

On the positive note I have to say that the K3 is well thought trough. I
feel comfortable with the physical layout and the radio is very easy to
operate. Most of the time I used the filters in shift/width mode, not LO/HI
and sometimes I was running with AGC off using RF-gain instead.

Would be interesting to hear others experience. With 600 radios out there,
there should be quite a few that's been exercised this weekend.

73 de Björn /SM0MDG & 7S0X

On 080331 15:31 , "Lee Buller" <[hidden email]> wrote:

>
> I would like to make a few comments and ask some questions. This is by no
> means a put-down of the the K3, because I am not sure I am operating the rig
> correctly. After all it is a SDR and it is new.
>
> During my first foray into SSB Contesting with the K3 during WPX, I found that
> I need either:
>
> 1. Understand more about the DSP and the controls for BW, Hcut and Lcut
>
> 2. Obtain a narrower roofing filter for SSB - like a 1.8 Khz filter
>
> 3. Or both.
>
> I spent some time trying to find the sweet spot in the radio for SSB using the
> 2.8 Khz filter. I don't think I found it. At least, I am not satisfied.
>
> I tried narrowing up the filter bandwidth to 2.4 or 2.2....some times 1.8.
> I tried shifting it up and down the bandpass.
> I tried to use High Cut and Low Cut depending on where the offending signal
> was coming from.
> AGC was on Slow with the standard settings.
> Used the RIT a lot
>
> It seemed I was always fighting some sort of side band splatter or stations
> close in on the frequency. Maybe it was just a crowded 20 meter band, but the
> same things happened on 40 meters.
>
> Do I need to go to a 1.8 Khz filter to give the DSP a break?
> Do I need to understand and play with the RX more to make sure I am doing it
> right.
>
> I would like to some feedback and comments on how other people set up their
> K3s for SSB contesting.
>
> I want to learn more about this radio.
>
> Lee - K0WA

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Matt Zilmer

Re: K3: SSB - WPX - Filters - Controls

FWIW, I run two SSB filters - 2.7 and 1.8 KHz. I find the 2.7 is fine
for ragchewing and light (no crowds) DXing and contesting. I can also
vouch for the 1.8 KHz roofing filter. It *kills* sidesplatter, esp.
when used judiciously with the DSP to clean up the passband edges. I
plan to substitute the 2.8 8-pole for the 2.7 one of these days, but
it's not a priority.

Eventually, you get used to pulling down the Hi Cut to rub out high
freq chatter. The 1.8 and DSP together are a very powerful
combination.

Also, FWIW - the human brain is The Ultimate Filter. NR can only help
compensate for its front-end input. That being said, the K3's NR is
the best I've heard in my limited 37-year ham experience.

73,
matt, W6NIA
K3 # 24

>Lee,

<snip>
>After the WPX
>experience I am now willing to try a sharper SSB filer, I think it is
>needed.
>
>I also tried noise reduction as higher bands sometimes where very noisy and
>signals weak. For me, DSP NR never really worked well. The NR in the K3
>seems to do a pretty nice job, but still my brain is far better.

<snip - back to Lee's original post>

>> Do I need to go to a 1.8 Khz filter to give the DSP a break?
>> Do I need to understand and play with the RX more to make sure I am doing it
>> right.
>>
>> I would like to some feedback and comments on how other people set up their
>> K3s for SSB contesting.
>>
>> I want to learn more about this radio.
>>
>> Lee - K0WA

hf4me

K3 Filter Configurations and Explanations

Thanks for bringing up the filter topic -

This is one of my main questions now. I finally ordered mine with no
optional filters and plan on adding them to the order before ship BUT I do
not know which will be the best for me. I suppose the answer to that is
that it will be different for everybody. I do expect to add the second
reciever board at some point, maybe not before initial ship.

Some sub-topics:

1) Is there any point in ordering the 200, 250, 400 and 500? Probably not.
Somebody explain how the filters are selected by the radio and recommend a
couple of reasonable configurations please. I want to be able to run PSK,
RTTY, CW and SSB and mainly I want to not have to deal with nearby signals,
I want them GONE.

2) a. Why would you order a 2.8 when you get a 2.7 with the radio?
b. Can you order the 2.8 instead of the standard 2.7 and receive "some"
credit for the 2.7 you didn't want?

3) Will the 1.8 make the SSB hard to understand vs possibly the 2.1? I
almost ordered the 1.8 but wasn't sure so didn't order anything yet.

4) What would be the best filter for RTTY?

5) Which filter will be best for PSK? A 6K filter or a 2.8 or narrower
looking at just part of the band at a time?

Pick one (or all) and give me your thoughts,

THANKS,
de Jim KG0KP (NewBee)

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Dick Dievendorff

RE: K3 Filter Configurations and Explanations

The most comprehensive writeup I've seen is here:
http://www.elecraft.com/K3/Roofing_Filters.htm

I'd agree that you probably don't want to order 200, 250, 400 and 500.
However two of these four makes sense for some buyers, including me.

If you configure the radio correctly, roofing filters are selected
automatically as you turn the "width" knob. You may also directly select a
roofing filter. I just twist the width knob to adjust the DSP bandwidth and
the appropriate roofing filter is selected for me.

One "reasonable" starting configuration is just the stock 2.7 KHz filter.
If you want to transmit AM, you'll need the 6.0 KHz AM filter. If FM is
important to you, you'll need the FM filter. I'm not currently interested
in transmitting in either of these modes, so I skipped those two filters and
I can receive AM with adequate (for me) fidelity by using my 2.8 KHz filter
and listening to one sideband. Discerning AM buffs might well have a
different definition of "adequate fidelity".

If you're interested in CW or "data" modes (RTTY, PSK, etc), then you'll
perhaps want to invest in one or more narrower filters, perhaps one or two
of 200, 250, 400, 500 Hz. If it's only one narrower filter, I'd suggest
either the 400 or 500 Hz filter. I think of the 200 and 250 as alternatives
and 400 and 500 as alternatives. I wouldn't think you'd want both 200 and
250 nor would you probably want both 400 and 500.

I personally don't think the difference between the 2.7 and 2.8 Hz filters
matters much, but I did choose all 8-pole filters. As a result I have
slightly wider SSB transmit bandwidth and sharper skirts on receive with the
2.8 KHz 8-pole filter.

I like the 1.0 KHz filter as a "normal" CW bandwidth in contest situations.
It's not so tight that I can't hear off-frequency callers.

The 1.8 KHz filter is a wonderful filter for phone contests and other
shoulder-to-shoulder situations on phone. Others prefer 2.1 KHz for their
narrowest SSB roofing filter. With the 1.8 I find that the off-frequency
crud often disappears, and the signal I'm isolating is comprehensible, but
"communications" fidelity rather than natural sounding.

I have to defer to the RTTY and PSK experts, but I think a 400 or 500 Hz
filter would be my 2nd filter (after the 2.7 or 2.8 decision).

My experience before the Elecraft K3 was with a series of up-converting ICOM
rigs including the 7800, whose narrowest roofing filter (after the roofing
filter upgrade) is 3 KHz.

I chose 8-pole filters at 2.8, 1.8, 1.0, 400, and 250. I probably have more
than I need for almost all situations. Most of my QSOs don't tax the
capability of any current-generation radio, but when the situation is very
competitive I don't want to be in mid-contest or mid-pileup and at that time
wish I'd spent the relatively small amount (compared to all the other
expenses in building a station) that these filters cost.

You don't have to decide all this at the time you receive the radio. You
can add roofing filters easily at a later date.

You just have to remove a handful of screws (top cover and half the bottom
cover), and the filter plugs in and is held in place by one lock washer and
nut. You might need to rearrange your existing filters when you add a new
one so that they're in a natural sequence.

Filter configuration takes a few minutes after you get the hang of it, and
it'll be even quicker with the next revision of the K3 Utility.

If you decide to add the 2nd receiver option, you'll need filter(s) for that
receiver as well. You might make the same decisions again or maybe not.
I'm going to make different choices for my 2nd receiver.

Sorry it's not a crisp answer. It's like a lot of topics, the answer is
always "it depends"...

73 de Dick, K6KR

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Jim Miller
Sent: Monday, March 31, 2008 8:59 PM
To: Elecraft Reflector
Subject: [Elecraft] K3 Filter Configurations and Explanations

Thanks for bringing up the filter topic -

This is one of my main questions now. I finally ordered mine with no
optional filters and plan on adding them to the order before ship BUT I do
not know which will be the best for me. I suppose the answer to that is
that it will be different for everybody. I do expect to add the second
reciever board at some point, maybe not before initial ship.

Some sub-topics:

1) Is there any point in ordering the 200, 250, 400 and 500? Probably not.
Somebody explain how the filters are selected by the radio and recommend a
couple of reasonable configurations please. I want to be able to run PSK,
RTTY, CW and SSB and mainly I want to not have to deal with nearby signals,
I want them GONE.

2) a. Why would you order a 2.8 when you get a 2.7 with the radio?
b. Can you order the 2.8 instead of the standard 2.7 and receive "some"
credit for the 2.7 you didn't want?

3) Will the 1.8 make the SSB hard to understand vs possibly the 2.1? I
almost ordered the 1.8 but wasn't sure so didn't order anything yet.

4) What would be the best filter for RTTY?

5) Which filter will be best for PSK? A 6K filter or a 2.8 or narrower
looking at just part of the band at a time?

Pick one (or all) and give me your thoughts,

THANKS,
de Jim KG0KP (NewBee)

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Bill W4ZV

RE: K3 Filter Configurations and Explanations

Dick Dievendorff wrote

If you're interested in CW or "data" modes (RTTY, PSK, etc), then you'll
perhaps want to invest in one or more narrower filters, perhaps one or two
of 200, 250, 400, 500 Hz. If it's only one narrower filter, I'd suggest
either the 400 or 500 Hz filter. I think of the 200 and 250 as alternatives
and 400 and 500 as alternatives. I wouldn't think you'd want both 200 and
250 nor would you probably want both 400 and 500.

The 400 and 250 are actually very close in bandwidth. According to Elecraft's own measurements below, the 400 actually has 435 Hz BW and the 250 is actually 370 Hz, both with the same shape factor. You definitely don't need to spend $250 total for two filters that only differ in BW by about 15%. Also note that the 2.7k actually has slightly wider BW than the 2.8k.

Filter BW(-6dB) Shape Factor
200 224 4.0
250 370 2.1
400 435 2.1
500 565 3.1
1000 1063 1.6
1800 1913 1.5
2700 2910 2.9
2800 2888 1.6
6000 6125 1.5

http://www.zerobeat.net/mediawiki/index.php/K3_Roofing_Filters

FYI my 2.7k/1.0k/500 are in close agreement with the above measurements but my 200 is slightly less than 210 Hz.

73, Bill W4ZV

w7aqk

Re: K3 Filter Configurations and Explanations

In reply to this post by Dick Dievendorff

I think Dick has put together an excellent summary regarding the available
filters. I sure don't see much to contradict based on my experience.

I would mention one thing, however, and i'm curious if others are
"experiencing" the same anomoly. I opted for both the 400 hz and the 200 hz
filters (in addition to the 2.7 khz and 6 khz filters). I am quite happy
with the 400 hz filter. Perhaps the 500 hz would have been sufficient, but
I do like the 400 hz just fine. My question is about the narrower
filters--the 200 hz and the 250 hz. I was almost certain I would use the
narrow filter fairly often. With other rigs I frequently found myself
trying to 'tighten" things down to eliminate QRM. However, I find myself
rarely needing to go down that far on the K3. I probably haven't really
given it the "acid test", like Field Day, but it does surprise me that I
tend to not even need something narrower. I can only attribute that to the
fact that the roofing filter system on the K3 is superior--that it does such
a good job compared to other receivers I don't have to fight QRM as much.

I'm not into the digital modes yet on any kind of serious basis, so maybe
that will turn out to be where the narrower filter proves to be most useful.

I would also be inclined to endorse Dick's suggestion of a 1 khz filter for
casual CW use. I don't have one though, so I can't say for sure. But I
strongly suspect it would be more pleasant to use. I like not having to go
too narrow, but QRM usually forced me to do so. But since these are roofing
filters, and not just crystal filters we usually rely on, I think QRM will
still be minimized. I am thinking seriously of ordering a 1 khz filter when
I get my 2nd receiver. If it works like I think it might, I may do some
reassessment of my filter complement in the 1st receiver. I'd be interested
in hearing how others with the 1 khz filter like using it.

Dave W7AQK

----- Original Message -----
From: "Dick Dievendorff" <[hidden email]>
To: "'Jim Miller'" <[hidden email]>; "'Elecraft Reflector'"
<[hidden email]>
Sent: Tuesday, April 01, 2008 12:17 AM
Subject: RE: [Elecraft] K3 Filter Configurations and Explanations

> The most comprehensive writeup I've seen is here:
> http://www.elecraft.com/K3/Roofing_Filters.htm
>
> I'd agree that you probably don't want to order 200, 250, 400 and 500.
> However two of these four makes sense for some buyers, including me.
>
> If you configure the radio correctly, roofing filters are selected
> automatically as you turn the "width" knob. You may also directly select
> a
> roofing filter. I just twist the width knob to adjust the DSP bandwidth
> and
> the appropriate roofing filter is selected for me.
>
> One "reasonable" starting configuration is just the stock 2.7 KHz filter.
> If you want to transmit AM, you'll need the 6.0 KHz AM filter. If FM is
> important to you, you'll need the FM filter. I'm not currently interested
> in transmitting in either of these modes, so I skipped those two filters
> and
> I can receive AM with adequate (for me) fidelity by using my 2.8 KHz
> filter
> and listening to one sideband. Discerning AM buffs might well have a
> different definition of "adequate fidelity".
>
> If you're interested in CW or "data" modes (RTTY, PSK, etc), then you'll
> perhaps want to invest in one or more narrower filters, perhaps one or two
> of 200, 250, 400, 500 Hz. If it's only one narrower filter, I'd suggest
> either the 400 or 500 Hz filter. I think of the 200 and 250 as
> alternatives
> and 400 and 500 as alternatives. I wouldn't think you'd want both 200 and
> 250 nor would you probably want both 400 and 500.
>
> I personally don't think the difference between the 2.7 and 2.8 Hz filters
> matters much, but I did choose all 8-pole filters. As a result I have
> slightly wider SSB transmit bandwidth and sharper skirts on receive with
> the
> 2.8 KHz 8-pole filter.
>
> I like the 1.0 KHz filter as a "normal" CW bandwidth in contest
> situations.
> It's not so tight that I can't hear off-frequency callers.
>
> The 1.8 KHz filter is a wonderful filter for phone contests and other
> shoulder-to-shoulder situations on phone. Others prefer 2.1 KHz for their
> narrowest SSB roofing filter. With the 1.8 I find that the off-frequency
> crud often disappears, and the signal I'm isolating is comprehensible, but
> "communications" fidelity rather than natural sounding.
>
> I have to defer to the RTTY and PSK experts, but I think a 400 or 500 Hz
> filter would be my 2nd filter (after the 2.7 or 2.8 decision).
>
> My experience before the Elecraft K3 was with a series of up-converting
> ICOM
> rigs including the 7800, whose narrowest roofing filter (after the roofing
> filter upgrade) is 3 KHz.
>
> I chose 8-pole filters at 2.8, 1.8, 1.0, 400, and 250. I probably have
> more
> than I need for almost all situations. Most of my QSOs don't tax the
> capability of any current-generation radio, but when the situation is very
> competitive I don't want to be in mid-contest or mid-pileup and at that
> time
> wish I'd spent the relatively small amount (compared to all the other
> expenses in building a station) that these filters cost.
>
> You don't have to decide all this at the time you receive the radio. You
> can add roofing filters easily at a later date.
>
> You just have to remove a handful of screws (top cover and half the bottom
> cover), and the filter plugs in and is held in place by one lock washer
> and
> nut. You might need to rearrange your existing filters when you add a new
> one so that they're in a natural sequence.
>
> Filter configuration takes a few minutes after you get the hang of it, and
> it'll be even quicker with the next revision of the K3 Utility.
>
> If you decide to add the 2nd receiver option, you'll need filter(s) for
> that
> receiver as well. You might make the same decisions again or maybe not.
> I'm going to make different choices for my 2nd receiver.
>
> Sorry it's not a crisp answer. It's like a lot of topics, the answer is
> always "it depends"...
>
> 73 de Dick, K6KR
>
>
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Jim Miller
> Sent: Monday, March 31, 2008 8:59 PM
> To: Elecraft Reflector
> Subject: [Elecraft] K3 Filter Configurations and Explanations
>
> Thanks for bringing up the filter topic -
>
> This is one of my main questions now. I finally ordered mine with no
> optional filters and plan on adding them to the order before ship BUT I do
> not know which will be the best for me. I suppose the answer to that is
> that it will be different for everybody. I do expect to add the second
> reciever board at some point, maybe not before initial ship.
>
> Some sub-topics:
>
> 1) Is there any point in ordering the 200, 250, 400 and 500? Probably not.
> Somebody explain how the filters are selected by the radio and recommend a
> couple of reasonable configurations please. I want to be able to run
> PSK,
> RTTY, CW and SSB and mainly I want to not have to deal with nearby
> signals,
> I want them GONE.
>
> 2) a. Why would you order a 2.8 when you get a 2.7 with the radio?
> b. Can you order the 2.8 instead of the standard 2.7 and receive "some"
> credit for the 2.7 you didn't want?
>
> 3) Will the 1.8 make the SSB hard to understand vs possibly the 2.1? I
> almost ordered the 1.8 but wasn't sure so didn't order anything yet.
>
> 4) What would be the best filter for RTTY?
>
> 5) Which filter will be best for PSK? A 6K filter or a 2.8 or narrower
> looking at just part of the band at a time?
>
> Pick one (or all) and give me your thoughts,
>
> THANKS,
> de Jim KG0KP (NewBee)
>
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Dick Dievendorff

RE: K3 Filter Configurations and Explanations

I acquired the 250 Hz filter primarily because a very good RTTY specialist
friend (W0YK) recommended it for contest RTTY. I haven't used it much. But
I haven't often used the 250 Hz bandwidth on any radio. My other radios had
uncompensated high filter loss with very narrow filters and I got into the
habit of getting narrow enough to remove the strongest interfering stations
and have tried to develop my aural discrimination capability for the rest.

In CW contest run situations 250 Hz is much too narrow. In CW contest S&P
situations I want to move quickly about and a narrow filter isn't well
suited to that. Since most of my operation is CW contests, the 250 Hz
filter doesn't get much use.

Fortunately with DSP filtering I can dial in just the width I want for any
situation and don't have to guess ahead of time exactly the final
selectivity I will want. The DSP does most of the work, and having a
corresponding width roofing filter (greatly) increases the capability of the
radio to deal with strong interference that is nearby. If the interfering
signal is within "reasonable" limits, the DSP alone can knock it down quite
well. Roofing filters show their value in situations where nearby
interfering signals are much stronger than the desired signal. The bands
during contests don't seem to be quite as full of thumps and crud with my K3
as they do with other, less capable equipment. During S&P, I find myself
tuning more slowly as I pass already-worked strong CQing stations, because
weaker nearby desired stations are now more audible.

If I sequenced the filters I currently have in the order of perceived need,
I'd have this order:

2.8 KHz because you must use a 2.7 or 2.8 KHz filter for CW and SSB
transmission; it's the general purpose SSB filter and wide CW filter.
400 Hz for "tight" CW or data modes.
1 KHz because I do much more CW than SSB, and this is about my general CW
width (most of my operation is during CW contests)
1.8 KHz because having this narrow capability makes phone contesting much
more pleasant and I can stay longer with less fatigue. I also like this
filter for "opened up" CW contest run situations. When I dial 1.2 KHz
bandwidth for CW running, this is the roofing filter I get.
250 Hz for rarely-encountered severe CW conditions or as-yet-unexperienced
data mode needs.

Although I haven't seen this explored publicly too much, you can configure
the roofing filter crossover points at bandwidths that differ slightly from
the bandwidth printed on the filter. If you study the available bandwidth
curves (or make curves of the filters you actually have), you can choose the
points at which the filters "kick in". If you think your 400 Hz filter is
really a 430 Hz filter, you might try configuring the K3 as if it had a 450
Hz filter, for example. You'll need to configure the 2.7 or 2.8 KHz filter
as 2.70, 2.75, or 2.80, and don't fiddle with the widths of the AM or FM
filters, but the rest are fair game.

Dick, K6KR

-----Original Message-----
From: David Yarnes [mailto:[hidden email]]
Sent: Tuesday, April 01, 2008 6:16 AM
To: [hidden email]; 'Jim Miller'; 'Elecraft Reflector'
Subject: Re: [Elecraft] K3 Filter Configurations and Explanations

I think Dick has put together an excellent summary regarding the available
filters. I sure don't see much to contradict based on my experience.

I would mention one thing, however, and i'm curious if others are
"experiencing" the same anomoly. I opted for both the 400 hz and the 200 hz

filters (in addition to the 2.7 khz and 6 khz filters). I am quite happy
with the 400 hz filter. Perhaps the 500 hz would have been sufficient, but
I do like the 400 hz just fine. My question is about the narrower
filters--the 200 hz and the 250 hz. I was almost certain I would use the
narrow filter fairly often. With other rigs I frequently found myself
trying to 'tighten" things down to eliminate QRM. However, I find myself
rarely needing to go down that far on the K3. I probably haven't really
given it the "acid test", like Field Day, but it does surprise me that I
tend to not even need something narrower. I can only attribute that to the
fact that the roofing filter system on the K3 is superior--that it does such

a good job compared to other receivers I don't have to fight QRM as much.

I'm not into the digital modes yet on any kind of serious basis, so maybe
that will turn out to be where the narrower filter proves to be most useful.

I would also be inclined to endorse Dick's suggestion of a 1 khz filter for
casual CW use. I don't have one though, so I can't say for sure. But I
strongly suspect it would be more pleasant to use. I like not having to go
too narrow, but QRM usually forced me to do so. But since these are roofing

filters, and not just crystal filters we usually rely on, I think QRM will
still be minimized. I am thinking seriously of ordering a 1 khz filter when

I get my 2nd receiver. If it works like I think it might, I may do some
reassessment of my filter complement in the 1st receiver. I'd be interested

in hearing how others with the 1 khz filter like using it.

Dave W7AQK

----- Original Message -----
From: "Dick Dievendorff" <[hidden email]>
To: "'Jim Miller'" <[hidden email]>; "'Elecraft Reflector'"
<[hidden email]>
Sent: Tuesday, April 01, 2008 12:17 AM
Subject: RE: [Elecraft] K3 Filter Configurations and Explanations

WA6L

Re: K3 Filter Configurations and Explanations

In reply to this post by hf4me

I can vouch that there is no reason to order both the 400 and 250 filters. When I first ordered my K3 on the phone, whomever I spoke with (and I can't remember) convinced me that these two would be the best combination for CW operation.

In reality, there is very little difference between the two filters and in actual operation I don't see the need for the 250. A better combination would be the 1000 and 400.

When calling CQ, I like to keep the BW set to around 800 to capture those signals that are not zero-beat. Once in a QSO or contest exchange, I can crank the BW down below 400 if needed. At least with the way I operate, the 1000/400 combo makes more sense.

So, I plan to order the 1000 filter. Anyone want a 250 filter at a good discount? Contact me offline.

73,

John, WA6L

Jim Miller-14 wrote

Thanks for bringing up the filter topic -

This is one of my main questions now. I finally ordered mine with no
optional filters and plan on adding them to the order before ship BUT I do
not know which will be the best for me. I suppose the answer to that is
that it will be different for everybody. I do expect to add the second
reciever board at some point, maybe not before initial ship.

Some sub-topics:

1) Is there any point in ordering the 200, 250, 400 and 500? Probably not.
Somebody explain how the filters are selected by the radio and recommend a
couple of reasonable configurations please. I want to be able to run PSK,
RTTY, CW and SSB and mainly I want to not have to deal with nearby signals,
I want them GONE.

2) a. Why would you order a 2.8 when you get a 2.7 with the radio?
b. Can you order the 2.8 instead of the standard 2.7 and receive "some"
credit for the 2.7 you didn't want?

3) Will the 1.8 make the SSB hard to understand vs possibly the 2.1? I
almost ordered the 1.8 but wasn't sure so didn't order anything yet.

4) What would be the best filter for RTTY?

5) Which filter will be best for PSK? A 6K filter or a 2.8 or narrower
looking at just part of the band at a time?

Pick one (or all) and give me your thoughts,

THANKS,
de Jim KG0KP (NewBee)

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AD6XY

Re: K3: SSB - WPX - Filters - Controls

In reply to this post by k0wa@swbell.net

I also noted the splatter problem - as well as the poor operators who are unable to listen properly (a station in Singapore) vs the good ones (an Italian) who can.

I think the reason for this close in rejection problem might be the shape factor of the DSP. In my case, it was not spatter as we normally think of it, but just getting rid of the adjacent channel without seriously compromising the wanted channel.

My K3 is worse in shape than my IC7400 but it depends on whether or not you use narrow or sharp mode of the IC7400. Luckily, I can install new firmware in the K3. I am sure shape factor adjustment is in the pipeline - or even already there but missed by me. The IC7400 is also a DSP based radio, but I have not seen any options to update the firmware. DSP is the place to fix this - I see no point at all in buying a 1.8kHz filter for SSB , it is just not necessary. If there is a signal 2kHz away inside the 2.7 but outside the 1.8 and 100dB above noise you are going to have problems with their IMDs anyway. No filter is going to help if the adjacent station is transmitting a wide signal.

NR is not helpful towards copying weak signals amongst strong QRM. That is not what it is for and you should be able to do much better without it than with it. NR comes into its own when the band is not so crowded but is noisy.

Ed Muns, W0YK

RE: K3 Filter Configurations and Explanations

In reply to this post by hf4me

Repeating what I've posted here previously, the first thing to get firmly in
mind about the K3 crystal filters is what their purpose is. They are not
used to determine the bandwidth you are using on any mode. (Yes, you need
the 2.7 or 2.8 for transmit on CW, RTTY and SSB. The AM and FM filters for
transmit on those modes.) Your receive bandwidth is determined by the DSP
filtering which is continually adjustable to any bandwidth you desire. The
Icom 756Pro series radios are excellent performers and have a single 15kHz
crystal filter. Narrower filtering is provided by the DSP just like the K3.

The purpose of the five easily-installable crystal filters in the K3 are to
pre-filter strong nearby signals so that the DSP can better do its excellent
job of the primary filtering. INRAD makes add-on "roofing filter" kits for
many radios and now has a 4-5kHz "roofing filter" kit for the Icom 756Pro
series for those people who are mostly interested in CW, RTTY and/or SSB.
This is a great improvement over the stock 15kHz filter for contesting and
situations where there are lots of very strong close-in signals.

You don't need any additional crystal filters in the K3 beyond the stock
2.7kHz filter to listen to CW at a 600Hz or 350Hz or 200Hz or whatever
bandwidth. Just dial in the width you want with the WIDTH, SHIFT, LO CUT
and/or HI CUT controls. You only need to consider additional crystal
filters if you operate in conditions where strong signals close to your
operating frequency (inside the 2.7kHz filter) may deteriorate the excellent
filtering of the DSP with IMD and other interference.

Because my primary Ham radio activity is contesting, having crystal filters
right at the bandwidths I use for each mode is useful. It is one of many
reasons why the K3 is my favorite contest radio. But all these filters are
not needed by many K3 users.

- For SSB, my default bandwidth is 1.5kHz and that is saved as ALT-1 and as
my standard SSB bandwidth on all my band-mode memories. Specifically, the
DSP filter is set at 300-1800kHz. I'm currently using the 1.8kHz crystal
filter which is actually about 1.9kHz at the -6dB points.

- For CW, my default bandwidth is 400Hz although I'd be just as happy at
500Hz. It's just that I'm currently using the 400Hz crystal filters. I
seldom go below that, but occasionally on 160 with heavy QRM I might go down
to 250 or 200Hz.

- For RTTY, my default bandwidth is 200Hz plus the Dual-Tone Filter of
additional cascaded 50Hz filters around each tone. In theory, the bandwidth
for 170Hz-shift RTTY should be 250-300Hz, but I've found operationally that
200Hz works great in my RTTY contesting.

Note that the actual -6dB bandwidths of the "400Hz" and "250Hz" filters are
435Hz and 370Hz respectively. You definitely don't need both of those
filters, although that's exactly what I personally have right now because I
failed to consider the actual bandwidths when making my initial selection.
Don't make that mistake.

Finally, you can set the point at which each crystal filter kicks in as the
DSP bandwidth is varied. I set my trigger points per the -6db bandwidths of
the various filters, not the product name. Thus, the "250Hz" filter
switches in at 350Hz because its actual bandwidth is 370Hz. Since I receive
RTTY at 200Hz DSP bandwidth, a better crystal filter for me in that mode
might be the "200Hz" (225Hz actual) for maximum strong signal protection.

73,
Ed - W0YK

> Thanks for bringing up the filter topic -
>
> This is one of my main questions now. I finally ordered mine
> with no optional filters and plan on adding them to the order
> before ship BUT I do not know which will be the best for me.
> I suppose the answer to that is that it will be different for
> everybody. I do expect to add the second reciever board at
> some point, maybe not before initial ship.
>
> Some sub-topics:
>
> 1) Is there any point in ordering the 200, 250, 400 and 500?
> Probably not.
> Somebody explain how the filters are selected by the radio
> and recommend a couple of reasonable configurations please.
> I want to be able to run PSK, RTTY, CW and SSB and mainly I
> want to not have to deal with nearby signals, I want them GONE.
>
> 2) a. Why would you order a 2.8 when you get a 2.7 with the radio?
> b. Can you order the 2.8 instead of the standard 2.7 and
> receive "some"
> credit for the 2.7 you didn't want?
>
> 3) Will the 1.8 make the SSB hard to understand vs possibly
> the 2.1? I almost ordered the 1.8 but wasn't sure so didn't
> order anything yet.
>
> 4) What would be the best filter for RTTY?
>
> 5) Which filter will be best for PSK? A 6K filter or a 2.8
> or narrower looking at just part of the band at a time?

Ed Muns, W0YK

RE: K3: SSB - WPX - Filters - Controls

In reply to this post by AD6XY

> I see no point at all in buying a
> 1.8kHz filter for SSB , it is just not necessary. If there is
> a signal 2kHz away inside the 2.7 but outside the
> 1.8 and 100dB above noise you are going to have problems with
> their IMDs anyway.

Few people will benefit from narrow SSB filters, but "no point at all" is
going too far. The 1.8kHz crystal filter is very effective for strong
signals in its stopband but still within the passband of a 2.7kHz filter,
e.g., a clean SSB signal 3kHz away. For most situations the additional
900Hz of IMD protection is not needed, but it is quite useful for serious
contesters trying to keep the rate up on crowded bands.

73,
Ed - W0YK

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Ed Muns, W0YK

RE: K3: SSB - WPX - Filters - Controls

In reply to this post by k0wa@swbell.net

In crowded band conditions, narrow filtering is often helpful. In
particular, for SSB contests, a receive bandwidth of 1500-1800Hz is very
effective. For me, 1500Hz (300-1800Hz) works great on the K3. There is no
intelligibility above 1800Hz that is useful in a contest QSO. If you think
200-2000Hz is easier to copy (1.8kHz bandwidth), then use that. But there
is no reason to use a 2.7 or 2.8kHz filter in a contest and letting in
another kHz or so of QRM.

Depending on preference some people like to narrow their SSB bandwidth by
using a combination of WIDTH and SHIFT. I prefer to simply reduce HI CUT
because the high audio frequencies (2000-3000Hz) are the least useful in
contest communication. So, it is a simple one-knob adjustment to narrow the
SSB bandwidth on receive.

You can select these narrow bandwidths with the K3 DSP and the stock 2.7kHz
crystal filter. You don't need narrow crystal filters unless you also want
protection from splatter and signal components from nearby strong signals
that fall between the bandwidth of the 2.7kHz filter and whatever narrower
crystal filter, e.g., 1.8kHz, you might use.

73,
Ed - W0YK

> During my first foray into SSB Contesting with the K3 during
> WPX, I found that I need either:
>
> 1. Understand more about the DSP and the controls for BW,
> Hcut and Lcut
>
> 2. Obtain a narrower roofing filter for SSB - like a 1.8 Khz filter
>
> 3. Or both.
>
> I spent some time trying to find the sweet spot in the radio
> for SSB using the 2.8 Khz filter. I don't think I found it.
> At least, I am not satisfied.
>
> I tried narrowing up the filter bandwidth to 2.4 or
> 2.2....some times 1.8.
> I tried shifting it up and down the bandpass.
> I tried to use High Cut and Low Cut depending on where the
> offending signal was coming from.
> AGC was on Slow with the standard settings.
> Used the RIT a lot
>
> It seemed I was always fighting some sort of side band
> splatter or stations close in on the frequency. Maybe it was
> just a crowded 20 meter band, but the same things happened on
> 40 meters.
>
> Do I need to go to a 1.8 Khz filter to give the DSP a break?
> Do I need to understand and play with the RX more to make
> sure I am doing it right.

Arie Kleingeld PA3A

RE: K3 Filter Configurations and Explanations

In reply to this post by Dick Dievendorff

Thanks to all for the comments. (I am using a 2x 400Hz and 2x 250 Hz
Inrad combo in my MP for selectivity at this time, and a wiiiiiide
roofing filter)

The subject is very interesting to me since I expect my K3 sometime in
June.

How about this one for the K3:
2.7 standard
2.1 8-pole SSB contesting
500 5-pole CW contest running
200 5-pole CW S&P especially 160m and 40m

The rationale: you don't need 8-pole since:
1. the interfering signals causing IMD don't have to be more than 20dB
down to stop the IMD.
2. If I use the DSP filtering, why add 8-pole filters if 1. applies
3. I read that the roofing filters can introduce IMD (because of steep
skirts or...? Is there a chance that 5-pole filters have less chance of
introducing IMD? Anybody can comment on this?)

I sure would like to hear the difference between 400 8-pole and 500
5-pole with fixed DSP bandwidth in a crowded strong signal band.

How about that?

73
Arie PA3A

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Ed Gray W0SD

Re: K3: SSB - WPX - Filters - Controls

In reply to this post by Ed Muns, W0YK

Why a 1.8 filter?

Well put Ed-W0YK. I am no electrical engineer, ie have no electronics
background, but I do my best to understand. In addition to what
Ed-W0YK mentioned there are at least a few more situations besides
contests for a 1.8 filter on receive for SSB. I have been on the bands
everyday working a lot of DX and I note the RTTY and CW and SSB DX
stations are more and more going to split frequency. Many are just
saying UP and many are saying up 1 and many SSB stations are just saying
up. I have no problem with this as it is best if the DX station does
not use anymore bandwidth than possible operating split. I can see why
they go split as "simplex" can be a real mess. The point is calling
stations are really getting close to the listening(DX)frequency. As we
move into a season of more sporadic E(can really be strong) on the
higher bands calling stations this close are going to be a problem as
they will be much louder than they are now. With hopefully more
sunspots down the road F2 signals more local will be very loud on 17M
and up. Even now on 20 meters and down they already often are loud so
we need all the IMD protection we can get. The l.8 filter roofing
filter with DSP can make a difference.

On CW, RTTY and SSB I think a number of people lose track how close they
are getting to the DX station and I often have stations on CW and RTTY
calling with in 300-500 hz and on SSB with in 1000 hz. What makes this
especially bad is they can call that close for a long time as they don't
get worked by the DX station. Having operated a number of DX-Peditions
I always made sure not to work anyone real close to my frequency and I
note others do the same to prevent station getting almost on top of the
DX stations frequency. Sometimes the calling stations figure it out that
they are to close and sometimes the "policeman" get them moved(not easy
as they often are not listening to their transmit frequency) but then
you have the policeman QRM.

Another thing that happens quite commonly is two DX stations with the
one having a listening frequency range that includes or gets extremely
close to the other DX stations frequency.

A second reason is a DX station operating split often accidentally gets
"TRASHED" by a very close station(usually does not know the DX station
is there) 1 or 2 Khz away or right on top of them and then there are the
"Policeman" trying to get them to move. It can be difficult to copy a DX
station even with reasonable strength when this happens. Obviously if
they are right on top there is nothing we can do with the rcv but often
they are not right on the frequency and the rcv comes into play.

A third possible reason that I am interested in finding out about under
actual operation is combating QRN on SSB with 1.8 and the proper AGC vs
a wider filter and the proper AGC. I think this somewhat depends on the
hearing from person to person but there is a lot of difference between
2.7 to 1.8 in filter width. This would mainly apply to 80 and 60 meters
I would think as there is little SSB on 160M on the low end but could
come into play higher in the band. I know from a lot of moonbounce
experience a narrower filter often helped as long as it was not to narrow.

A fourth reason which has often been mentioned is if you have hams that
live close to you! Admittedly they are not likely to operate that close
to you normally that the difference in filters would make any difference
but you both might want to chase the same DX station at the same time as
sometimes the window to a rare one is just 10 or 15 minutes a day and
the DX station is just listening in a narrow range up a little. In this
situation the other station can be pinning your meter so you need all
the help you can get!

Fifth even if you don't work DX or Contest but have any schedules or
just get on and call CQ and ragchew so often even after asking several
times if the frequency is in use some one can get very close to you and
also band conditions change. Also if you like nets it is not at all
unusual to have a very strong station interfering with NCS and other
stations on frequency. Maybe it is because I live in the middle of the
country but QRM very close in frequency is a constant issue for me;
especially on SSB no matter what type of operation I am doing.

Obviously as W0YK said it depends on what type of operating you do. If
you only do cw, digital and rarely if ever get on SSB then the 1.8
filter is not needed. If you get on SSB much at all to me it seems to
make economic sense to eventually get a 1.8 or 2.1 filter for receive
given we are not talking about a lot of money difference, maybe 4% -7%
of the total price. IMHO on SSB receive the major advantage a K3 has
over any other radio on the market would be the narrower roofing filter
than the competition. The only other advantages I can see on SSB over
others might be a more effective NR/NB but of course that only comes
into play if you have noise. There may be an advantage in lower DSP
noise, AGC hangup, etc. based on what Bob Sherwood found. Not having my
K3's yet(I ordered two as you just can not argue with the spec's and
experience of knowledgeable operators)I am not sure about these last two
but comments from very knowledgeable posts here indicate there may be
some advantages now and possibly more down the road with firmware
updates in these two areas over any other radios on SSB. The advantages
on CW, RTTY, etc. are obvious. The good news you can add a roofing
filter at any time.

Since it has been consistently pointed out the DSP does a good job past
the -30 db points of the roofing filter being used I made the following
chart from various sources on the Elecraft sites. Looking at the -30 db
points we see the following figures for filter width:

1.8 Filter 8 pole 2500 hz
2.1 Filter 8 pole 3200 hz (700 hz more than 1.8 filter)
2.7 Filter 5 pole 5600 hz (3100hz more than 1.8 filter)
2.8 Filter 8 pole 3400 hz (900 hz more than 1.8 filter)

Looking at the -6db points we see the following figures for filter width:
1.8 Filter 8 pole 1913 hz
2.1 Filter 8 pole 2175 hz (262 hz more than 1.8 filter)
2.7 Filter 5 pole 2910 hz (997 hz more than 1.8 filter)
2.8 Filter 8 pole 2888 hz (975 hz more than 1.8 filter)

The following information came from Eric WA6HHQ of Elecraft 13-09-07
post, 8 pole plots posted by Elecraft, 5 pole info from OH9HB plot for
200 & 500 hz. filters. There could be a slight error in my ability to
read the points on the plots but they are close. Hopefully I did not
make any typo's or incorrect subtractions!

Filter Pole BW(-6db) -3db** -30db -60db*** Shape factor
200 5 224 200 500 860 4.0
250 8 370 430 785 2.1
400 8 435 640 935 2.1
500 5 565 465 1100 1680 3.1
1000 8 1063 1400 1650 1.6
1800 8 1913 2500 2863 1.5
2100 8 2175 3200 3213 1.5
2700 5 2910 2710 5600 8439* 2.9
2800 8 2888 3400 4488 1.6

* calculated
** source Eric WA6HHQ 13-09-07 post
***Really not a significant factor with DSP and the K3 design

In closing I defer to the electronic experts on the significance of
these figures in day to day ham radio operation. I understand the point
that bad signals with real output inside the filter can be the limiting
factor if the difference in filter width is not large but to me 997 hz
at -3 db and 3100 hz at -30db between the 1.8 and 2.7 filter is quite
large even for SSB. We can not control how other set their transmitter
but at least when someone is "clean" it seems to me that the 1.8 or 2.1
filter will give a noticeable advantage even with the DSP since these
two filters are narrower at -6db all the way to -30 db. Given the shape
factor of 2.9 for the 2.7 filter it widens out quite rapidly from -6 db
to -30db points where the other two have a shape factor of 1.5 and do
not widen out nearly as fast. Even stations that are not clean the 1.8
filter should permit us to hear closer to them than the 2.7 filter.

Therefore with the 1.8 filter we get 997 hz more protection from strong
signals at -6 db and 3100 hz more protection at -30 db over the 2.7 five
pole "STOCK" filter. For the 2.8 eight pole filter we get 975 hz more
protection at -6 db and 900 hz at -30db from strong signals.

73, Ed W0SD

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S Sacco

Re: K3: SSB - WPX - Filters - Controls

In reply to this post by Ed Muns, W0YK

Why a 1.8 kHz filter?

Despite the belief that DSP can accomplish all things, it's not
necessarily true.

After experimenting around with only the 2.8 kHz filter for SSB, I
decided that I didn't like the way the DSP version of the 1.8 kHz
bandwidth sounded; it had a slight "ringiness" to it. I ordered a 1.8
filter on a Thursday afternoon, and it was in my mailbox on Monday.

The sound was definitely more pleasant to my ears.

Remember - we are analog beings, not digital.

73,

Steve NN4X
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Bill Maddock-2

Re: K3 Filter Configurations and Explanations

In reply to this post by WA6L

John,

I ordered the 500 hz and 250hz filters The 500
will be great for the casual stuff. When it
gets tough like the 160 mtr contest with signals
30 and 40 db over S9 all over that 250 will be
king. I have 2 TS-850S with inrad 400 hz - they
are ok but I assume that when my K3 arrives I
won't here the next guy blasting me off to the
side that much anymore. the 250 hz will defintely
have it's place. Likewise I hope that the 2.1
will work better than the 850S on SSB!

This will make my contesting so much more enjoyable!

73,

Bill N4ZI

--- WA6L <[hidden email]> wrote:

>
>
> I can vouch that there is no reason to order both
> the 400 and 250 filters.
> When I first ordered my K3 on the phone, whomever I
> spoke with (and I can't
> remember) convinced me that these two would be the
> best combination for CW
> operation.
>
> In reality, there is very little difference between
> the two filters and in
> actual operation I don't see the need for the 250.
> A better combination
> would be the 1000 and 400.
>
> When calling CQ, I like to keep the BW set to around
> 800 to capture those
> signals that are not zero-beat. Once in a QSO or
> contest exchange, I can
> crank the BW down below 400 if needed. At least
> with the way I operate, the
> 1000/400 combo makes more sense.
>
> So, I plan to order the 1000 filter. Anyone want a
> 250 filter at a good
> discount? Contact me offline.
>
> 73,
>
> John, WA6L
>
>
>
> Jim Miller-14 wrote:
> >
> > Thanks for bringing up the filter topic -
> >
> > This is one of my main questions now. I finally
> ordered mine with no
> > optional filters and plan on adding them to the
> order before ship BUT I do
> > not know which will be the best for me. I suppose
> the answer to that is
> > that it will be different for everybody. I do
> expect to add the second
> > reciever board at some point, maybe not before
> initial ship.
> >
> > Some sub-topics:
> >
> > 1) Is there any point in ordering the 200, 250,
> 400 and 500? Probably not.
> > Somebody explain how the filters are selected by
> the radio and recommend a
> > couple of reasonable configurations please. I
> want to be able to run
> > PSK,
> > RTTY, CW and SSB and mainly I want to not have to
> deal with nearby
> > signals,
> > I want them GONE.
> >
> > 2) a. Why would you order a 2.8 when you get a 2.7
> with the radio?
> > b. Can you order the 2.8 instead of the standard
> 2.7 and receive "some"
> > credit for the 2.7 you didn't want?
> >
> > 3) Will the 1.8 make the SSB hard to understand
> vs possibly the 2.1? I
> > almost ordered the 1.8 but wasn't sure so didn't
> order anything yet.
> >
> > 4) What would be the best filter for RTTY?
> >
> > 5) Which filter will be best for PSK? A 6K filter
> or a 2.8 or narrower
> > looking at just part of the band at a time?
> >
> > Pick one (or all) and give me your thoughts,
> >
> > THANKS,
> > de Jim KG0KP (NewBee)
> >
> > _______________________________________________
> > Elecraft mailing list
> > Post to: [hidden email]
> > You must be a subscriber to post to the list.
> > Subscriber Info (Addr. Change, sub, unsub etc.):
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>
> >
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> > Elecraft web page: http://www.elecraft.com
> >
> >
>
> --
> View this message in context:
>

http://www.nabble.com/K3%3A--SSB---WPX---Filters---Controls-tp16399464p16418680.html

> Sent from the Elecraft mailing list archive at
> Nabble.com.
>
> _______________________________________________
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Joe Subich, W4TV-3

RE: K3 Filter Configurations and Explanations

In reply to this post by Ed Muns, W0YK

> - For RTTY, my default bandwidth is 200Hz plus the Dual-Tone
> Filter of additional cascaded 50Hz filters around each tone.
> In theory, the bandwidth for 170Hz-shift RTTY should be
> 250-300Hz, but I've found operationally that 200Hz works
> great in my RTTY contesting.

The two 50 Hz filters spaced 170 Hz would have a total bandwidth
of 230Hz. This is very close to the "published" value of 224 Hz
for the 5-pole filter (I intend to measure mine when it arrives
later this week). However, I wonder if it would not be useful
to modify the 200 Hz filter - or for Elecraft to offer a "real"
250 Hz filter using the values shown in the K3 schematic pack
(page 7).

Based on the published 224 Hz (and reports of 210 Hz) and 4:1
shape factor a "250 Hz" 5-pole filter would still offer much
better performance between -6dB and - 30 dB than the "250 Hz
8 pole" filter but a "real" 250 Hz wide filter should be just
enough wider to eliminate potential "sharpening" of the dual-
tone (DSP) filter.

My filter choices - and I'll see if I guessed right in a week
or so - were FM, 2.8 KHz, 500 Hz and 200 Hz. I'm leaving the
one slot open for 2.1, 1.8 or possibly a variable SSB filter
if/when that is available. The FM filter was chosen for general
non-critical listening (including AM) as it is still narrower
than the front end filter in any of the mid-grade "up-conversion"
receivers. I know I will want something "between" 2.8 and 500 Hz
and suspect the 1.8 will fill the bill for general CW on a quiet
band and for "click on the waterfall" PSK31 operation.

73,

... Joe, W4TV

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Ed Muns
> Sent: Tuesday, April 01, 2008 2:33 PM
> To: 'Jim Miller'
> Cc: 'Elecraft Reflector'
> Subject: RE: [Elecraft] K3 Filter Configurations and Explanations
>
>
> Repeating what I've posted here previously, the first thing
> to get firmly in mind about the K3 crystal filters is what
> their purpose is. They are not used to determine the
> bandwidth you are using on any mode. (Yes, you need the 2.7
> or 2.8 for transmit on CW, RTTY and SSB. The AM and FM
> filters for transmit on those modes.) Your receive bandwidth
> is determined by the DSP filtering which is continually
> adjustable to any bandwidth you desire. The Icom 756Pro
> series radios are excellent performers and have a single
> 15kHz crystal filter. Narrower filtering is provided by the
> DSP just like the K3.
>
> The purpose of the five easily-installable crystal filters in
> the K3 are to pre-filter strong nearby signals so that the
> DSP can better do its excellent job of the primary filtering.
> INRAD makes add-on "roofing filter" kits for many radios and
> now has a 4-5kHz "roofing filter" kit for the Icom 756Pro
> series for those people who are mostly interested in CW, RTTY
> and/or SSB. This is a great improvement over the stock 15kHz
> filter for contesting and situations where there are lots of
> very strong close-in signals.
>
> You don't need any additional crystal filters in the K3
> beyond the stock 2.7kHz filter to listen to CW at a 600Hz or
> 350Hz or 200Hz or whatever bandwidth. Just dial in the width
> you want with the WIDTH, SHIFT, LO CUT and/or HI CUT
> controls. You only need to consider additional crystal
> filters if you operate in conditions where strong signals
> close to your operating frequency (inside the 2.7kHz filter)
> may deteriorate the excellent filtering of the DSP with IMD
> and other interference.
>
> Because my primary Ham radio activity is contesting, having
> crystal filters right at the bandwidths I use for each mode
> is useful. It is one of many reasons why the K3 is my
> favorite contest radio. But all these filters are not needed
> by many K3 users.
>
> - For SSB, my default bandwidth is 1.5kHz and that is saved
> as ALT-1 and as my standard SSB bandwidth on all my band-mode
> memories. Specifically, the DSP filter is set at
> 300-1800kHz. I'm currently using the 1.8kHz crystal filter
> which is actually about 1.9kHz at the -6dB points.
>
> - For CW, my default bandwidth is 400Hz although I'd be just
> as happy at 500Hz. It's just that I'm currently using the
> 400Hz crystal filters. I seldom go below that, but
> occasionally on 160 with heavy QRM I might go down to 250 or 200Hz.
>
> - For RTTY, my default bandwidth is 200Hz plus the Dual-Tone
> Filter of additional cascaded 50Hz filters around each tone.
> In theory, the bandwidth for 170Hz-shift RTTY should be
> 250-300Hz, but I've found operationally that 200Hz works
> great in my RTTY contesting.
>
> Note that the actual -6dB bandwidths of the "400Hz" and
> "250Hz" filters are 435Hz and 370Hz respectively. You
> definitely don't need both of those filters, although that's
> exactly what I personally have right now because I failed to
> consider the actual bandwidths when making my initial
> selection. Don't make that mistake.
>
> Finally, you can set the point at which each crystal filter
> kicks in as the DSP bandwidth is varied. I set my trigger
> points per the -6db bandwidths of the various filters, not
> the product name. Thus, the "250Hz" filter switches in at
> 350Hz because its actual bandwidth is 370Hz. Since I receive
> RTTY at 200Hz DSP bandwidth, a better crystal filter for me
> in that mode might be the "200Hz" (225Hz actual) for maximum
> strong signal protection.
>
> 73,
> Ed - W0YK
>
> > Thanks for bringing up the filter topic -
> >
> > This is one of my main questions now. I finally ordered mine
> > with no optional filters and plan on adding them to the order
> > before ship BUT I do not know which will be the best for me.
> > I suppose the answer to that is that it will be different for
> > everybody. I do expect to add the second reciever board at
> > some point, maybe not before initial ship.
> >
> > Some sub-topics:
> >
> > 1) Is there any point in ordering the 200, 250, 400 and 500?
> > Probably not.
> > Somebody explain how the filters are selected by the radio
> > and recommend a couple of reasonable configurations please.
> > I want to be able to run PSK, RTTY, CW and SSB and mainly I
> > want to not have to deal with nearby signals, I want them GONE.
> >
> > 2) a. Why would you order a 2.8 when you get a 2.7 with the radio?
> > b. Can you order the 2.8 instead of the standard 2.7 and
> > receive "some"
> > credit for the 2.7 you didn't want?
> >
> > 3) Will the 1.8 make the SSB hard to understand vs possibly
> > the 2.1? I almost ordered the 1.8 but wasn't sure so didn't
> > order anything yet.
> >
> > 4) What would be the best filter for RTTY?
> >
> > 5) Which filter will be best for PSK? A 6K filter or a 2.8
> > or narrower looking at just part of the band at a time?
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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> Elecraft web page: http://www.elecraft.com

Joe Subich, W4TV-3

RE: K3 Filter Configurations and Explanations

In reply to this post by Arie Kleingeld PA3A

> 1. the interfering signals causing IMD don't have to be more
> than 20dB down to stop the IMD. 2.

On the other hand the 2.8 KHz 8 pole filter is actually narrower
than the 2.7 KHz 5 pole (2.888 KHz vs. 2910 KHz from previously
published data) with significantly sharper skirts so the -30 dB
widths are roughly 3.755 KHz for the 2.8 KHz filter vs. 5.675 KHz
for the 2.7 KHz filter.

> If I use the DSP filtering, why add 8-pole filters if 1. applies
> 3. I read that the roofing filters can introduce IMD (because of
> steep skirts or...? Is there a chance that 5-pole filters have
> less chance of introducing IMD?

The signal level thorough the roofing filters is quite high. With
high signal levels, the crystals need to be exceptionally clean
and well behaved. Eric tells me that the 8 pole filters are
specially selected by INRAD for low IMD characteristics (the lower
grade filters go into FT-1000/FT-1000MPs). Elecraft to a special
"burn in" of their crystals before building the 5 pole filters.
Still, the filter IMD (due to non-linearity in the crystals) may
be up to 2 dB better with the 8 pole filters than with the 5 pole
units.

73,

... Joe, W4TV

> If I use the DSP
> filtering, why add 8-pole filters if 1. applies 3. I read
> that the roofing filters can introduce IMD (because of steep
> skirts or...? Is there a chance that 5-pole filters have less
> chance of introducing IMD? Anybody can comment on this?)

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Arie
> Kleingeld PA3A
> Sent: Tuesday, April 01, 2008 5:32 PM
> To: 'Elecraft Reflector'
> Subject: RE: [Elecraft] K3 Filter Configurations and Explanations
>
>
> Thanks to all for the comments. (I am using a 2x 400Hz and 2x
> 250 Hz Inrad combo in my MP for selectivity at this time, and
> a wiiiiiide roofing filter)
>
> The subject is very interesting to me since I expect my K3
> sometime in June.
>
>
> How about this one for the K3:
> 2.7 standard
> 2.1 8-pole SSB contesting
> 500 5-pole CW contest running
> 200 5-pole CW S&P especially 160m and 40m
>
> The rationale: you don't need 8-pole since:
> 1. the interfering signals causing IMD don't have to be more
> than 20dB down to stop the IMD. 2. If I use the DSP
> filtering, why add 8-pole filters if 1. applies 3. I read
> that the roofing filters can introduce IMD (because of steep
> skirts or...? Is there a chance that 5-pole filters have less
> chance of introducing IMD? Anybody can comment on this?)
>
> I sure would like to hear the difference between 400 8-pole
> and 500 5-pole with fixed DSP bandwidth in a crowded strong
> signal band.
>
> How about that?
>
> 73
> Arie PA3A
>
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