[GreenKeys] Re: ah-haa, found some rtty!
Gregory W. Moore
[email protected]
Fri, 13 Jun 2003 19:37:23 -0400
GE, Gil
Ok, now, the way it works is the hypothetical center frequency of the
FSK pair should be located at the
center of the 3Khz sideband. Ok lets say that the actual listed freq
is 14.097. The center freq of the sideband
is 14.0955, which is where you would set the window freq if you were
working SSB. Now, to get the window freq for
center of the FSK (or AFSK, makes no never mind with SSB, for all
practical intents and purposes they are identical), you
take the frequency shift, halve it, and subtract that from the center
freq of the sideband.
OK here goes Listed Freq= 14.097.0
Half of the sideband width= (1.5)
Window freq for SSB use= 14095.5
Now, depending on the shift and mode, the actual center freq of the FSK
(AFSK) signal is going to be slightly down from
that, and if you don't know the actual shift, just look at your
waterfall, you already have a good idea of what tone pairs will
be transmitted, and either tune until the tone pairs are in the right
place on the AF spectrum, or simply click on the tone pairs and the
hairlines will shift to the working frequency.. It will be unnnoticable
at the other end...either way works ok,
I use the shift method and channelize a freq for the proper tone pair in
use, so that all I have to do is go to the next channel, and the FSK
(AFSK) sigs are right where they should be. (for a 170 Hz shift, its
800Hz down from the center, and so on).
This works for me, and since I recieve MARS traffic, I can set this up,
dial the freq in, set my antenna tuner to the presets
I have already worked out, and very little tuning is needed.. All I
really have to do, is sometime before the net, just check with the "Tune
Transmitter" option, and tweak the inductance a little to make sure I
have a good signal and a low SWR.
hope this helps.
73 de Greg WA3IVX
gil smith wrote:
> Hey! I got an ARRL RTTY broadcast on 14.095! My first reception of clear
>text, which resulted in a BFG (big f'n grin)!
>
>My freq display actually showed about 14.097; can they be off that much?
>This is a Kenwood TS-430S, which I presume uses a synthesizer. Of course
>the reference xtal would be off a bit, not sure how much is typical. Is
>there a way to run it off of an external reference signal? Then I could
>use an HP sig gen to keep it exact.
>
>I went to check the other freqs listed on the schedule, but there was
>nothing there. Then I returned to 14.095, and it was also gone (about 20
>mins after the hour, so maybe the broadcast was done). Didn't matter, I
>was a happy camper!
>
>Then I found some hams chatting, somewhere around 14.088 or so. Lots of
>fun to see -- discussion about some hal tus, so maybe they are even using
>iron.
>
>Ahh, made my weekend! Must be time for a beer.
>
>thanks to all for your help,
>
>gil (radio newbie) smith
>
>
>
>;-----------------------------------------------------------
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>; http://www.vauxelectronics.com (fax: 480-354-5558)
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--
"All that is necessary for the triumph of evil is that good men do nothing."
--Edmund Burke
Greg Moore NNN0BVN PA
U.S. Navy-Marine Corps Military Affiliate Radio System (MARS)
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