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K3 SSB filters

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John Simmons

K3 SSB filters

With the recent experience in SSB contests, I'm thinking of upgrading
my SSB filter(s). Currently for SSB I have only the 2.8 filter. What are
thoughts about other SSB filters? I know when I narrow the bandwidth to
1.8 the intelligibility goes down.

-de John NI0K
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Re: K3 SSB filters

Hi John,

There’s a nice writeup from Wayne and Eric here:

https://elecraft.com/pages/k3s-crystal-roofing-filters

Perhaps that will help. It certainly helped me.

73 de AG7TX

David Thompson, AG7TX
Jack of All Trades
Master of None
[hidden email]

> On Mar 31, 2020, at 08:00, John Simmons <[hidden email]> wrote:
>
> With the recent experience in SSB contests, I'm thinking of upgrading my SSB filter(s). Currently for SSB I have only the 2.8 filter. What are thoughts about other SSB filters? I know when I narrow the bandwidth to 1.8 the intelligibility goes down.
>
> -de John NI0K
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Bob McGraw - K4TAX

Re: K3 SSB filters

In reply to this post by John Simmons

I have, in my K3S, the standard 2.7 kHz filter for transmit and often
use the 1.8 kHz filter for receive to deal with QRM. It is necessary to
adjust the SHIFT in order to improve copy when the 1.8 kHz filter is
active. Yes, this is perfectly normal, the 1.8 kHz filter is not going
to allow the audio to be Hi-Fi quality. That's the nature of
"communications quality" audio.

73

Bob, K4TAX

On 3/31/2020 10:00 AM, John Simmons wrote:

> With the recent experience in SSB contests, I'm thinking of upgrading
> my SSB filter(s). Currently for SSB I have only the 2.8 filter. What
> are thoughts about other SSB filters? I know when I narrow the
> bandwidth to 1.8 the intelligibility goes down.
>
> -de John NI0K
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Nate Bargmann

Re: K3 SSB filters

In reply to this post by John Simmons

I typically use Hi Cut the most, Lo Cut once in a while and almost never
use Width in SSB mode. For me the 2.1 kHz filter works swell in this
application.

In the late '90s I bought a TS-850s which was fitted with a 1.8 kHz
factory accessory filter. I couldn't get rid of it fast enough and
outfitted the radio with Inrad 2.1 kHz filters. They were far more
pleasing to me.

73, Nate, N0NB

--

"The optimist proclaims that we live in the best of all
possible worlds. The pessimist fears this is true."

Web: https://www.n0nb.us
Projects: https://github.com/N0NB
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Bob McGraw - K4TAX

Re: K3 SSB filters

Remember, different brands of 2.1 or 1.8 filters are not necessarily equal. One must realize the shape factor is more important than the published BW. Just because one radio filter is 1.8 kHz does not mean another 1.8 kHz BW is the same.

Bob, K4TAX

Sent from my iPhone

> On Mar 31, 2020, at 7:02 PM, Nate Bargmann <[hidden email]> wrote:
>
> I typically use Hi Cut the most, Lo Cut once in a while and almost never
> use Width in SSB mode. For me the 2.1 kHz filter works swell in this
> application.
>
> In the late '90s I bought a TS-850s which was fitted with a 1.8 kHz
> factory accessory filter. I couldn't get rid of it fast enough and
> outfitted the radio with Inrad 2.1 kHz filters. They were far more
> pleasing to me.
>
> 73, Nate, N0NB
>
> --
>
> "The optimist proclaims that we live in the best of all
> possible worlds. The pessimist fears this is true."
>
> Web: https://www.n0nb.us
> Projects: https://github.com/N0NB
> GPG fingerprint: 82D6 4F6B 0E67 CD41 F689 BBA6 FB2C 5130 D55A 8819
>
> ______________________________________________________________
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Don Wilhelm

Re: K3 SSB filters

Hopefully that we will remember that the DSP filter skirts are steeper
than the crystal filter skirts, so judicious use of the HiCut and LoCut
will provide us with a better passband than narrow roofing filters.

What the roofing filters will do is keep the receiver from reducing the
hardware AGC for stations which are within the roofing filter passband.
It takes adjacent signals in excess of S-9 +30 for the adjacent signal
to activate the hardware AGC (which protects the front end DAC from
overload). If the interfering station does not exceed that threshold,
then the DSP filters will take care of it, and the need for more narrow
roofing filters is superfluous.

73,
Don W3FPR

On 3/31/2020 8:57 PM, Bob McGraw K4TAX wrote:

> Remember, different brands of 2.1 or 1.8 filters are not necessarily equal. One must realize the shape factor is more important than the published BW. Just because one radio filter is 1.8 kHz does not mean another 1.8 kHz BW is the same.
>
> Bob, K4TAX
>
>
> Sent from my iPhone
>
>> On Mar 31, 2020, at 7:02 PM, Nate Bargmann <[hidden email]> wrote:
>>
>> I typically use Hi Cut the most, Lo Cut once in a while and almost never
>> use Width in SSB mode. For me the 2.1 kHz filter works swell in this
>> application.
>>
>> In the late '90s I bought a TS-850s which was fitted with a 1.8 kHz
>> factory accessory filter. I couldn't get rid of it fast enough and
>> outfitted the radio with Inrad 2.1 kHz filters. They were far more
>> pleasing to me.
>>
>> 73, Nate, N0NB
>>
>> --
>>
>> "The optimist proclaims that we live in the best of all
>> possible worlds. The pessimist fears this is true."
>>
>> Web: https://www.n0nb.us
>> Projects: https://github.com/N0NB
>> GPG fingerprint: 82D6 4F6B 0E67 CD41 F689 BBA6 FB2C 5130 D55A 8819
>>
>> ______________________________________________________________
>> 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]
>>
>
>
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Jim Brown-10

Re: K3 SSB filters

On 3/31/2020 8:36 PM, Don Wilhelm wrote:
> What the roofing filters will do is keep the receiver from reducing the
> hardware AGC for stations which are within the roofing filter passband.

In addition, when the DSP IF filters are set to about the same width as
the roofing filters, the two filters "cascade" -- the rejection of
adjacent signals is the sum of the rejection of the two filters.

73, Jim K9YC
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David Gilbert

Re: K3 SSB filters

In reply to this post by Don Wilhelm

No, the roofing filters aren't superfluous even with lower level
signals. If you set the bandwidths similarly as I do all of the time,
the rejection of the filter adds to the rejection from the DSP. I think
this should be pretty obvious.

Dave AB7E

On 3/31/2020 8:36 PM, Don Wilhelm wrote:

> Hopefully that we will remember that the DSP filter skirts are steeper
> than the crystal filter skirts, so judicious use of the HiCut and
> LoCut will provide us with a better passband than narrow roofing filters.
>
> What the roofing filters will do is keep the receiver from reducing
> the hardware AGC for stations which are within the roofing filter
> passband.
> It takes adjacent signals in excess of S-9 +30 for the adjacent signal
> to activate the hardware AGC (which protects the front end DAC from
> overload). If the interfering station does not exceed that threshold,
> then the DSP filters will take care of it, and the need for more
> narrow roofing filters is superfluous.
>
> 73,
> Don W3FPR

john@kk9a.com

Re: K3 SSB Filters

In reply to this post by John Simmons

I concur. I have 2.8, 2.1 and 1.8 KHz 8 pole roofing filters in my
K3S. I made over 8500 SSB QSOs last month and I used the 2.1 KHz
roofing filter for all of them.

John KK9A

Jim Brown K9YC wrote:

I tried that and didn't like the result. I prefer 2.1 kHz 8 pole

73, Jim K9YC

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Elecraft mailing list

Re: K3 SSB Filters

John, I concur. When I am running them especially on 20M I find I have the
LO Cut at .35 and the HI Cut at 2.25-2.35. Audio is good. Below 2.25 if the
calling station is a little off freq or has terrible audio I may waste time
trying to get the call.
N2TK, Tony

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of [hidden email]
Sent: Wednesday, April 1, 2020 7:30 AM
To: [hidden email]
Subject: Re: [Elecraft] K3 SSB Filters

I concur. I have 2.8, 2.1 and 1.8 KHz 8 pole roofing filters in my K3S. I
made over 8500 SSB QSOs last month and I used the 2.1 KHz roofing filter for
all of them.

John KK9A

Jim Brown K9YC wrote:

I tried that and didn't like the result. I prefer 2.1 kHz 8 pole

73, Jim K9YC

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Wes Stewart-2

Re: K3 SSB filters

In reply to this post by Jim Brown-10

Until you get down to the noise floor isn't it always the sum (in dB) of the
rejection?

Wes N7WS

On 3/31/2020 8:52 PM, Jim Brown wrote:
> On 3/31/2020 8:36 PM, Don Wilhelm wrote:
>> What the roofing filters will do is keep the receiver from reducing the
>> hardware AGC for stations which are within the roofing filter passband.
>
> In addition, when the DSP IF filters are set to about the same width as the
> roofing filters, the two filters "cascade" -- the rejection of adjacent
> signals is the sum of the rejection of the two filters.
>
> 73, Jim K9YC

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Leroy

Glad you are OK

In reply to this post by Don Wilhelm

Good to learn something from you today Don,
Thanks 73, Leroy AB7CE

-----Original Message-----
From: Don Wilhelm
Sent: Tuesday, March 31, 2020 9:36 PM
To: [hidden email]
Subject: Re: [Elecraft] K3 SSB filters

Hopefully that we will remember that the DSP filter skirts are steeper
than the crystal filter skirts, so judicious use of the HiCut and LoCut
will provide us with a better passband than narrow roofing filters.

What the roofing filters will do is keep the receiver from reducing the
hardware AGC for stations which are within the roofing filter passband.
It takes adjacent signals in excess of S-9 +30 for the adjacent signal
to activate the hardware AGC (which protects the front end DAC from
overload). If the interfering station does not exceed that threshold,
then the DSP filters will take care of it, and the need for more narrow
roofing filters is superfluous.

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Jim Brown-10

Re: K3 SSB filters

In reply to this post by Wes Stewart-2

On 4/1/2020 7:17 AM, Wes wrote:
> Until you get down to the noise floor isn't it always the sum (in dB) of
> the rejection?

Isn't that what I said? Perhaps I said it badly.

73, Jim
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Wes Stewart-2

Re: K3 SSB filters

You said: "In addition, when the DSP IF filters are set to about the same width
as the roofing filters, the two filters "cascade" -- the rejection of adjacent
signals is the sum of the rejection of the two filters. "

There is no requirement that the widths be about the same. They could be widely
different. If one passes an interfering signal with no attenuation and the
other has 100 dB rejection then the sum is 0 + 100 = 100. Either could be first
in the lineup.

If the K3 second mixer was stronger, hardware AGC might not be necessary and the
only need for a "roofing" filter would be to eliminate the image. A single
10-12 kHz filter would suffice and DSP would be the final filter. Sounds like a
K4HD doesn't it?

On 4/1/2020 10:23 AM, Jim Brown wrote:
> On 4/1/2020 7:17 AM, Wes wrote:
>> Until you get down to the noise floor isn't it always the sum (in dB) of the
>> rejection?
>
> Isn't that what I said? Perhaps I said it badly.
>
> 73, Jim

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