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K3S filter for FT8?

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Frank O'Donnell

K3S filter for FT8?

I'm sure this is a well-covered question, but I'm getting so many hits
on search terms that it's difficult to find past discussions.

On the K3S or K3, what filter(s) are people finding optimal for FT8? Due
to its popularity, it seems as though the FT8 bandwidth has been
gradually widening.

Thanks and 73,

Frank O'Donnell K6FOD

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Barry LaZar

Re: K3S filter for FT8?

Frank,
All of FT8 is supposed to fit in a voice grade channel, 2.1 KHz
-3.0KHz. The S/N numbers you see are referenced to a 2.5 KHz. B/W.
However, having said that, there are some operators that go out to just
short of 3.0 KHz. I leave my receiver open to this larger number. If
your question is really asking what is the signal bandwidth that is a
different question than I just answered. My recommendation is to set
your DSP bandwidth, the knob selectable B/W, equal to the roofing filter
B/W plus just a little and not worry too much about it. You will see the
majority of signals and the software will see the available calls and
stations calling you. The downside is greater interference and some AGC
issues caused by some station you really didn't want to work anyway.

I'm not trying to be glib in answering you in the latter part of my
comment above, but there is no easy single answer. I do believe most
everyone is operating as I do, within the SSB filters of their radio.

73,
Barry
K3NDM

------ Original Message ------
From: "Frank O'Donnell" <[hidden email]>
To: "[hidden email]" <[hidden email]>
Sent: 5/5/2019 5:54:34 PM
Subject: [Elecraft] K3S filter for FT8?

>I'm sure this is a well-covered question, but I'm getting so many hits on search terms that it's difficult to find past discussions.
>
>On the K3S or K3, what filter(s) are people finding optimal for FT8? Due to its popularity, it seems as though the FT8 bandwidth has been gradually widening.
>
>Thanks and 73,
>
>Frank O'Donnell K6FOD
>
>
>______________________________________________________________
>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

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Bob McGraw - K4TAX

Re: K3S filter for FT8?

In reply to this post by Frank O'Donnell

I find 2.7 kHz to be optimized. The software does the heavy lifting. And the software has limits on the low and high frequency tones.

If you use the new FT-4 mode it uses slightly different frequencies on each band.

Bob, K4TAX

Sent from my iPhone

> On May 5, 2019, at 4:54 PM, Frank O'Donnell <[hidden email]> wrote:
>
> I'm sure this is a well-covered question, but I'm getting so many hits on search terms that it's difficult to find past discussions.
>
> On the K3S or K3, what filter(s) are people finding optimal for FT8? Due to its popularity, it seems as though the FT8 bandwidth has been gradually widening.
>
> Thanks and 73,
>
> Frank O'Donnell K6FOD
>
>
> ______________________________________________________________
> 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
>

ANDY DURBIN

K3S filter for FT8?

In reply to this post by Frank O'Donnell

"However, having said that, there are some operators that go out to just short of 3.0 KHz."

I monitor with 4 kHz or 5 kHz bandwidth and sometime call up there just to see if anyone thinks the same way I do. That's a habit formed when working JT65+JT9. You sometimes find interesting stations to work well above 2.7 kHz. Working out to 5 kHz is no issue with a TS-590 as long as WSJT-X and the rig are configured for split.

73,
Andy, k3wyc
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jh3sif

Re: K3S filter for FT8?

Having enabled 13kHz roofing filter for digital modes, i enlarge K3 DSP filter width to 4kHz for watching FT8/JT65 and PSKs.

73 de JH3SIF, Keith

> 2019/05/06 8:02、Andy Durbin <[hidden email]>のメール:
>
> "However, having said that, there are some operators that go out to just short of 3.0 KHz."
>
> I monitor with 4 kHz or 5 kHz bandwidth and sometime call up there just to see if anyone thinks the same way I do. That's a habit formed when working JT65+JT9. You sometimes find interesting stations to work well above 2.7 kHz. Working out to 5 kHz is no issue with a TS-590 as long as WSJT-X and the rig are configured for split.
>
> 73,
> Andy, k3wyc
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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Joe Subich, W4TV-4

Re: K3S filter for FT8?

In reply to this post by Frank O'Donnell

> On the K3S or K3, what filter(s) are people finding optimal for FT8?

The AM or FM filters allow setting a DSP bandwidth of slightly more than
4 KHz. WSJT-X handles that just fine and is handy when activity spreads
out a bit. For me this is a carryover from dual mode JT65/JT9 activity
predating both FT8 and now FT4.

73,

... Joe, W4TV

On 2019-05-05 5:54 PM, Frank O'Donnell wrote:

> I'm sure this is a well-covered question, but I'm getting so many hits
> on search terms that it's difficult to find past discussions.
>
> On the K3S or K3, what filter(s) are people finding optimal for FT8? Due
> to its popularity, it seems as though the FT8 bandwidth has been
> gradually widening.
>
> Thanks and 73,
>
> Frank O'Donnell K6FOD
>

Bill Frantz

Re: K3S filter for FT8?

In reply to this post by Frank O'Donnell

I run FT8 wide open with a 4KHz bandwidth and the 13KHz FM
filter in the K3. I would go even wider, but the K3 stops at
4KHz. The AM filter might be better, but there are only 5 filter
slots, and I try to work in many modes. A really good day
includes phone, CW, and digital QSOs.

73 Bill AE6JV

On 5/5/19 at 2:54 PM, [hidden email] (Frank O'Donnell) wrote:

>I'm sure this is a well-covered question, but I'm getting so
>many hits on search terms that it's difficult to find past discussions.
>
>On the K3S or K3, what filter(s) are people finding optimal for
>FT8? Due to its popularity, it seems as though the FT8
>bandwidth has been gradually widening.
-----------------------------------------------------------------------
Bill Frantz |The nice thing about standards| Periwinkle
(408)356-8506 |is there are so many to choose| 16345
Englewood Ave
www.pwpconsult.com |from. - Andrew Tanenbaum | Los Gatos,
CA 95032

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Jim Brown-10

Re: K3S filter for FT8?

In reply to this post by Frank O'Donnell

On 5/5/2019 2:54 PM, Frank O'Donnell wrote:
> On the K3S or K3, what filter(s) are people finding optimal for FT8?

IF selectivity is provided in DSP, not with plug-in filters as with
older radios. Plug-in filters for these radios are ROOFING filters --
they protect the DSP from overload from strong signals outside the
chosen IF bandwidth.

Nearly all WSJT modes are designed to work with the full bandwidth of an
SSB channel -- about 2.7 kHz, which is the bandwidth of the stock
roofing filter that comes with a K3 or K3S. In fact, Joe Taylor, K1JT
has long advised that rigs should always be set for that wide bandwidth
for his modes, and let WSJT-X do the required signal processing to
separate stations.

There's a fundamental reason for that -- for most physical networks, and
for digital simulation of physical networks and devices, any change in
amplitude response has an associated change in the phase response.
Decoding systems, including the human hearing system, are degraded by
steeply changing phase response. We learned about this in pro audio
world in the '70s, thanks to the work and teaching of the late Richard
Heyser. THAT'S why Joe advises as he does. In the last few years, RTTY
operators have learned this and taken it to heart. Gone are the
recommendations for "double-humped" filters, with their associated phase
distortion -- the top operators now use 400-500 Hz filters for RTTY.

A major shortcoming of the K2 is that when the multi-stage crystal
filter is realigned for narrow SSB bandwidth, the frequency response
looks like a cross-section of the rocky mountains, making SSB speech
more difficult to copy. The radio sounds great when the TX filter is
used for RX, which is at full SSB bandwidth.

73, Jim K9YC

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