[Elecraft] RTTY filter for K3

[n4lq]

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



_________________________________________________________________
Discover the new Windows Vista
http://search.msn.com/results.aspx?q=windows+vista&mkt=en-US&form=QBRE_______________________________________________
Elecraft mailing list
Post to: Elecraft at mailman.qth.net
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


--------------------------------------------------------------------------------



No virus found in this incoming message.
Checked by AVG.
Version: 8.0.100 / Virus Database: 269.23.20/1452 - Release Date: 5/17/2008 
6:26 PM