[Elecraft] RTTY filter for K3

Sun May 18 14:09:11 EDT 2008

I'm using DATA A mode. Contrary to the manual, the Dual Tone RTTY filter 
will not activate in DATA A mode. When attempted, the display shows N/A.
To use the DTF, I changed to AFSK A mode. This allows the DTF to work 
however the center frequency of the IF changes from 1500Hz to 1356Hz. I will 
notify Elecraft about these.
As far as copying RTTY with the 200hz filter and DTF....It appears to work 
fine. The only difference I could detect on the waterfall with DTF turned on 
is the obvious "hole" between the filter peaks.

Steve Ellington
N4LQ at insightbb.com
----- Original Message ----- 
From: "K3KO" <alsopb at nc.rr.com>
To: <elecraft at mailman.qth.net>
Sent: Sunday, May 18, 2008 10:12 AM
Subject: Re: [Elecraft] RTTY filter for K3

>
> Please turn on the K3 dual peak RTTY filter and tell us what you see then.
> Brian/K3KO
>
>
> n4lq wrote:
>>
>> Axel
>> I was the first to respond to your question. I told you that I was
>> listening
>> to RTTY through the 200 Hz, 5 pole filter and it worked fine. Then the
>> experts came on here and using many words, explained why it couldn't work
>> because it is too narrow. Maybe they do not actually have the filter but 
>> I
>> do.
>> Looking at the waterfall on MixW, 200Hz filter engaged, a RTTY signal
>> easily
>> fits within the waterfall's passband with a little room on either side.
>> The
>> vertical stripes of the RTTY signal do not quiet reach the outer edge of
>> the
>> waterfall which tells me that the "data" is not being chopped off. Both
>> weak
>> and strong RTTY signals seem perfectly copyable.
>> No I would not use this in a contest unless I had a bandscope so I could
>> find signals. I have ordered the LP-PAN which should take care of that
>> little detail.
>> 73
>>
>> Steve Ellington
>> N4LQ at insightbb.com
>> ----- Original Message ----- 
>> From: "Axel Kaiser" <dl2sca at hotmail.com>
>> To: "Elecraft Reflector" <elecraft at mailman.qth.net>
>> Sent: Sunday, May 18, 2008 4:14 AM
>> Subject: [Elecraft] RTTY filter for K3
>>
>>
>>
>>
>>
>>
>> To all you filter aficionados,
>>
>> first of all thank you very much for all your detailed answers to my
>> original question, which roofing filter ist best for RTTY operation of 
>> the
>> K3. Lots of very detailed and informative answers were given and even a
>> general discussion on this issue among several others was started. But to
>> tell you the truth, I am still somewhat uncertain, which filter to order
>> with my K3.
>> One of my theory books about HF technology, modulation, bandwidth and so
>> forth, tells me, that the necessary bandwidth for a 170 Hz shift RTTY
>> signal
>> should be around 320 Hz. Now some of you guys write, that you are using a
>> 250 Hz filter for RTTY operation. A 250 Hz filter though has this 250 Hz
>> (ok, a few Hz more in reality) bandwidth at - 6dB attenuation, which 
>> means
>> that the actual bandwidth at about 0 db is even less.
>> So my understanding for a 170 Hz shift RTTY operation is, to use a filter
>> of
>> at least 400 - 500 Hz (at -6dB) in order to get all the information
>> through
>> the filter. This I can confirm also with my current OMNI VI+ which does
>> not
>> allow me to copy RTTY signals with a 250 Hz filter . So please, where is
>> the
>> point which I am missing with the K3, that you can work weak RTTY signals
>> with a 250 Hz roofing filter??
>>
>> Best 73 de
>>
>> Axel, DL3ZH
>>
>>
>>
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>
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