[Elecraft] RTTY filter for K3

[David Wilburn]

I think it is just the difference between books and the real world.  I 
run AFSK, and with the K3 setup you can make full use of the filters. 
  If I want to drill into a signal the 400hz works well.  You leave a 
little drop off on each side.  If you get it too narrow, the signal 
does not decode well.  If you have issues beyond that, like I had when 
I hand two signals intermixing, then I went to the dual-pass-band 
filter, and that nails it down pretty hard.

I have the 400hz, 1.0khz, newley received 1.8khz, and the 2.7khz, and 
it worked great in the volta rtty contest, and have used it some on 
20m Friday evening.  I am very happy with the setup.

Start out with the 400hz, and put it in the second slot.  If you want 
to add a 250 later, it takes about 15m to do it.


Dave Wilburn
K4DGW
K2/100 - S/N 5982
K3/100 - S/N 766

"For those who fought for it, freedom has a flavor the protected will 
never know."


Axel Kaiser wrote:
> 
> 
> 
> 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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