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K3: best roofing filter on RTTY

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K3: best roofing filter on RTTY

Hi Guys,

I'd appreciate your thoughts on the best roofing filter: 250hz vs. 400hz,
for RTTY contest conditions.

While I really like the K3 on RTTY, I believe improvement can be made to
my K3 RTTY reception. Some contesters have told me that they use the 250hz
roofing filter exclusively when operating RTTY contests. Since the actual
bandwidth of the 250hz roffer filter is close to 370hz, and RTTY signals
are typically about 370hz wide, then the 250hz roofer along with a 400 or
500hz DSP setting should be close to ideal when maximum selectivity is
needed. However, on both of my K3's, when I switch from the 400hz roofer to the
250hz roofer, the RTTY signal is decoded a lot less often, about 25% less
often. It doesn't seem like the 400hz roofer should decode 25% more often
than the 250hz roofer. (but perhaps that's normal?)

Perhaps there is a receiver setting change I can make to the K3 that will
improve RTTY decoding when using the 250hz roofer? I've tried various
shift settings when the 250hz roofer is engaged and sometimes it improves RTTY
reception, but not consistantly. Perhaps there's a setting change I can
make to MMTTY?
By the way, I'm using both MMTTY and 2Tone software's for decoding RTTY,
with basically the same results when the 250hz roofer is engaged.

Thanks in advance for your thoughts.

73,
Dick- K9OM

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Jim Rhodes-3

Re: K3: best roofing filter on RTTY

I have always been happy with my 400's. There seems to be very little
bandbass not filled by the signal. Although many folks seem to like the
250's I don't have any so I use the 400's on what CW I do too.
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NK7Z

Re: K3: best roofing filter on RTTY

In reply to this post by Elecraft mailing list

Hi,
I ordered and use the 400 for RTTY, I suspect the 250 is a bit to
narrow.
--
Thanks and 73's,
For equipment, and software setups and reviews see:
www.nk7z.net
for MixW support see;
http://groups.yahoo.com/neo/groups/mixw/info
for Dopplergram information see:
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for MM-SSTV see:
http://groups.yahoo.com/neo/groups/MM-SSTV/info

On Sun, 2015-02-15 at 22:02 -0500, Dick via Elecraft wrote:

> Hi Guys,
>
> I'd appreciate your thoughts on the best roofing filter: 250hz vs. 400hz,
> for RTTY contest conditions.
>
> While I really like the K3 on RTTY, I believe improvement can be made to
> my K3 RTTY reception. Some contesters have told me that they use the 250hz
> roofing filter exclusively when operating RTTY contests. Since the actual
> bandwidth of the 250hz roffer filter is close to 370hz, and RTTY signals
> are typically about 370hz wide, then the 250hz roofer along with a 400 or
> 500hz DSP setting should be close to ideal when maximum selectivity is
> needed. However, on both of my K3's, when I switch from the 400hz roofer to the
> 250hz roofer, the RTTY signal is decoded a lot less often, about 25% less
> often. It doesn't seem like the 400hz roofer should decode 25% more often
> than the 250hz roofer. (but perhaps that's normal?)
>
>
> Perhaps there is a receiver setting change I can make to the K3 that will
> improve RTTY decoding when using the 250hz roofer? I've tried various
> shift settings when the 250hz roofer is engaged and sometimes it improves RTTY
> reception, but not consistantly. Perhaps there's a setting change I can
> make to MMTTY?
> By the way, I'm using both MMTTY and 2Tone software's for decoding RTTY,
> with basically the same results when the 250hz roofer is engaged.
>
>
> Thanks in advance for your thoughts.
>
> 73,
> Dick- K9OM
>
>
>
>
> ______________________________________________________________
> 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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Wes (N7WS)

Re: K3: best roofing filter on RTTY

Me too.

On 2/15/2015 11:35 PM, David Cole wrote:
> Hi,
> I ordered and use the 400 for RTTY, I suspect the 250 is a bit to
> narrow.

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Jim Sheldon

Re: K3: best roofing filter on RTTY

In reply to this post by Elecraft mailing list

The narrowest filter I have in both receivers is the 400 Hz one. I
borrowed a K3 that had a 250 Hz filter in it once and tried it on RTTY.
It works, but it's right on the margin of being too narrow. If someone
is using one of the older Packet TNC's that have RTTY mode in them (they
used 200 Hz shift instead of 170 and there are still a lot of them out
there) it's really hard to get them tuned in with a 250 Hz filter,
especially in weak signal/selective QSB situations. The 400 Hz filter
doesn't seem to have that limitation though it does let slightly more
noise in (easily handled with the DSP filters anyway.

Jim - W0EB

>
>On 2/15/2015 11:35 PM, David Cole wrote:
>>Hi,
>>I ordered and use the 400 for RTTY, I suspect the 250 is a bit to
>>narrow.
>
>______________________________________________________________
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ve3dvy

Re: K3: best roofing filter on RTTY

In reply to this post by Elecraft mailing list

David Moes
VE3DVY

Since I find that the 8 pole 250 Hz filter is really a bit wider I
tell my K3 in filter setups its 300hz It works fine for me this way
including on RTTY

During the WPXRTTY this weekend I had good luck copying weak signals
right beside a power house signal using the 250hz filter.

>
> --- Original message ---
> Subject: Re: [Elecraft] K3: best roofing filter on RTTY
> From: Jim's Desktop <[hidden email]>
> To: <[hidden email]>
> Date: Monday, 16/02/2015 9:49 AM
>
> The narrowest filter I have in both receivers is the 400 Hz one. I
> borrowed a K3 that had a 250 Hz filter in it once and tried it on
> RTTY.
> It works, but it's right on the margin of being too narrow. If
> someone
> is using one of the older Packet TNC's that have RTTY mode in them
> (they
> used 200 Hz shift instead of 170 and there are still a lot of them out
> there) it's really hard to get them tuned in with a 250 Hz filter,
> especially in weak signal/selective QSB situations. The 400 Hz filter
> doesn't seem to have that limitation though it does let slightly more
> noise in (easily handled with the DSP filters anyway.
>
> Jim - W0EB
>>
>>
>> On 2/15/2015 11:35 PM, David Cole wrote:
>>>
>>> Hi,
>>> I ordered and use the 400 for RTTY, I suspect the 250 is a bit to
>>> narrow.
>>

Ted Edwards W3TB

Re: K3: best roofing filter on RTTY

I also like the 400 Hz filter, but when tuning around like in this
weekend's CQ WPX RTTY then I went much wider.
With that width came lots of noise. What is a good idea on that?
And thanks ahead of time.

On Mon, Feb 16, 2015 at 12:47 PM, <[hidden email]> wrote:

>
>
>
> David Moes
> VE3DVY
>
> Since I find that the 8 pole 250 Hz filter is really a bit wider I tell
> my K3 in filter setups its 300hz It works fine for me this way including
> on RTTY
>
> During the WPXRTTY this weekend I had good luck copying weak signals
> right beside a power house signal using the 250hz filter.
>
>
>> --- Original message ---
>> Subject: Re: [Elecraft] K3: best roofing filter on RTTY
>> From: Jim's Desktop <[hidden email]>
>> To: <[hidden email]>
>> Date: Monday, 16/02/2015 9:49 AM
>>
>> The narrowest filter I have in both receivers is the 400 Hz one. I
>> borrowed a K3 that had a 250 Hz filter in it once and tried it on RTTY.
>> It works, but it's right on the margin of being too narrow. If someone
>> is using one of the older Packet TNC's that have RTTY mode in them (they
>> used 200 Hz shift instead of 170 and there are still a lot of them out
>> there) it's really hard to get them tuned in with a 250 Hz filter,
>> especially in weak signal/selective QSB situations. The 400 Hz filter
>> doesn't seem to have that limitation though it does let slightly more
>> noise in (easily handled with the DSP filters anyway.
>>
>> Jim - W0EB
>>
>>>
>>>
>>> On 2/15/2015 11:35 PM, David Cole wrote:
>>>
>>>>
>>>> Hi,
>>>> I ordered and use the 400 for RTTY, I suspect the 250 is a bit to
>>>> narrow.
>>>>
>>>
>>>
> ______________________________________________________________
> 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]
>

--
73 de Ted Edwards, W3TB and GØPWW

and thinking about operating CW:
"Do today what others won't,
so you can do tomorrow what others can't."
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Richard Ferch

Re: K3: best roofing filter on RTTY

In reply to this post by Elecraft mailing list

If you take the "250 Hz" marketing name of the filter too seriously and
set it to switch in at a DSP bandwidth of 250 Hz, then yes, it is
perhaps too narrow for comfortable use with RTTY. On the other hand, if
you set the filter to switch in at 350 Hz, the combination of the "250
Hz" filter with a 350 Hz DSP bandwidth seems to work quite well for RTTY
when QRM is heavy. When QRM is not quite so bad, you may get better
decoding results using wider bandwidths in both the roofing filter and
the DSP.

73,
Rich VE3KI

W0EB wrote:

> The narrowest filter I have in both receivers is the 400 Hz one. I
> borrowed a K3 that had a 250 Hz filter in it once and tried it on RTTY.
> It works, but it's right on the margin of being too narrow. If someone
> is using one of the older Packet TNC's that have RTTY mode in them (they
> used 200 Hz shift instead of 170 and there are still a lot of them out
> there) it's really hard to get them tuned in with a 250 Hz filter,
> especially in weak signal/selective QSB situations. The 400 Hz filter
> doesn't seem to have that limitation though it does let slightly more
> noise in (easily handled with the DSP filters anyway.

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Elecraft mailing list

Re: K3: best roofing filter on RTTY

In reply to this post by ve3dvy

I attended Contest University at Dayton last year and the RTTY expert
suggested he found that too narrow a filter compromised the decoding.
It seemed to work best when the filter was a little wider. He suggested
500Hz and 250Hz only in the presence of strong QRM. He did NOT like the
dual-tone filtering in the K3 or Icom's twin-peak filter.

It is on slide 3 of the Advanced RTTY Contesting presentation available
in the Files section on the Contest University website.

Buck
k4ia
K3# 101 KX3 #715

On 2/16/2015 12:47 PM, [hidden email] wrote:

>
>
>
> David Moes
> VE3DVY
>
> Since I find that the 8 pole 250 Hz filter is really a bit wider I
> tell my K3 in filter setups its 300hz It works fine for me this way
> including on RTTY
>
> During the WPXRTTY this weekend I had good luck copying weak signals
> right beside a power house signal using the 250hz filter.
>>
>> --- Original message ---
>> Subject: Re: [Elecraft] K3: best roofing filter on RTTY
>> From: Jim's Desktop <[hidden email]>
>> To: <[hidden email]>
>> Date: Monday, 16/02/2015 9:49 AM
>>
>> The narrowest filter I have in both receivers is the 400 Hz one. I
>> borrowed a K3 that had a 250 Hz filter in it once and tried it on RTTY.
>> It works, but it's right on the margin of being too narrow. If someone
>> is using one of the older Packet TNC's that have RTTY mode in them (they
>> used 200 Hz shift instead of 170 and there are still a lot of them out
>> there) it's really hard to get them tuned in with a 250 Hz filter,
>> especially in weak signal/selective QSB situations. The 400 Hz filter
>> doesn't seem to have that limitation though it does let slightly more
>> noise in (easily handled with the DSP filters anyway.
>>
>> Jim - W0EB
>>>
>>>
>>> On 2/15/2015 11:35 PM, David Cole wrote:
>>>>
>>>> Hi,
>>>> I ordered and use the 400 for RTTY, I suspect the 250 is a bit to
>>>> narrow.
>>>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

Jim Brown-10

Re: K3: best roofing filter on RTTY

On Mon,2/16/2015 2:38 PM, K4ia via Elecraft wrote:
> I attended Contest University at Dayton last year and the RTTY expert
> suggested he found that too narrow a filter compromised the decoding.
> It seemed to work best when the filter was a little wider.

That same expert used to recommend narrower filter and dual-peak IF. I
always thought that was a bad idea on the basis of the additional phase
shift introduced by the narrower filter and the dual peaks, but no one
believed that until G3YYD, author of the new and very nice RTTY decoder,
said so. :)

I have the 250 Hz 8-pole and 400 Hz 8-pole filters. I switch in the 250
Hz filter at 350 Hz and the 400 Hz filter at 500 Hz. Most of the time, I
set the IF to 400 Hz for RTTY and 250 Hz for CW. The only times I'll go
narrower for RTTY is with very strong QRM very close to my frequency.

73, Jim K9YC

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ve3dvy

Re: K3: best roofing filter on RTTY

In reply to this post by Elecraft mailing list

I left it there because I am using a pan adapter to find stations. so
I don't need to see anything wider on MMTTY display. but before I
had it I would toggle between wide and narrow filter width as needed
by pressing [hold] the width control knob

David Moes
VE3DVY

> --- Original message ---
> Subject: Re: [Elecraft] K3: best roofing filter on RTTY
> From: Ted Edwards W3TB <[hidden email]>
> To: <[hidden email]>
> Cc: Elecraft Reflector <[hidden email]>
> Date: Monday, 16/02/2015 2:01 PM
>
>
>
> I also like the 400 Hz filter, but when tuning around like in this
> weekend's CQ WPX RTTY then I went much wider.
>
> With that width came lots of noise. What is a good idea on that?
>
> And thanks ahead of time.
>
>
> On Mon, Feb 16, 2015 at 12:47 PM, <[hidden email]> wrote:
>>
>>
>>
>>
>> David Moes
>> VE3DVY
>>
>> Since I find that the 8 pole 250 Hz filter is really a bit wider I
>> tell my K3 in filter setups its 300hz It works fine for me this way
>> including on RTTY
>>
>> During the WPXRTTY this weekend I had good luck copying weak signals
>> right beside a power house signal using the 250hz filter.
>>
>>>
>>>
>>> --- Original message ---
>>> Subject: Re: [Elecraft] K3: best roofing filter on RTTY
>>> From: Jim's Desktop <[hidden email]>
>>> To: <[hidden email]>
>>> Date: Monday, 16/02/2015 9:49 AM
>>>
>>> The narrowest filter I have in both receivers is the 400 Hz one. I
>>> borrowed a K3 that had a 250 Hz filter in it once and tried it on
>>> RTTY.
>>> It works, but it's right on the margin of being too narrow. If
>>> someone
>>> is using one of the older Packet TNC's that have RTTY mode in them
>>> (they
>>> used 200 Hz shift instead of 170 and there are still a lot of them out
>>> there) it's really hard to get them tuned in with a 250 Hz filter,
>>> especially in weak signal/selective QSB situations. The 400 Hz filter
>>> doesn't seem to have that limitation though it does let slightly more
>>> noise in (easily handled with the DSP filters anyway.
>>>
>>> Jim - W0EB
>>>>
>>>>
>>>>
>>>> On 2/15/2015 11:35 PM, David Cole wrote:
>>>>>
>>>>>
>>>>> Hi,
>>>>> I ordered and use the 400 for RTTY, I suspect the 250 is a bit to
>>>>> narrow.
>>>>
>>
>> ______________________________________________________________
>> 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]
>
>
>
> --
>
>
>
> 73 de Ted Edwards, W3TB and GØPWW
>
> and thinking about operating CW:
> "Do today what others won't,
> so you can do tomorrow what others can't."

John Bastin-2

Re: K3: best roofing filter on RTTY

In reply to this post by Elecraft mailing list

> On 15 Feb 2015, at 22:02, Dick via Elecraft <[hidden email]> wrote:
>
> Perhaps there is a receiver setting change I can make to the K3 that will
> improve RTTY decoding when using the 250hz roofer? I've tried various
> shift settings when the 250hz roofer is engaged and sometimes it improves RTTY
> reception, but not consistantly. Perhaps there's a setting change I can
> make to MMTTY?

I'm using the MMTTY engine with WriteLog for contesting, and I find the 400Hz roofing filter, used together with the Dual Passband selection gives good RTTY reception along with good results dealing with QRM.

Hope this helps.

John K8AJS
[hidden email]

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