[GreenKeys] on-off radio teletype (not FSK)

[tony.podrasky]

Hey Jack;

What year did you get started on RTTY?

UE,
K2EAA - TONY
NNNN
ZCZC


On 02/17/2018 08:38 AM, Jack wrote:
> When I first got onto RTTY, I was 13 years old and had no idea what I was
> doing.
> (I'm much older now and still have no idea what I'm doing...)
>
> I built the "Twin Cities TU" from the "New RTTY Handbook" using junk parts
> from old TV sets.  I originally used an output transformer primary as my
> MARK "tuned circuit"
> with a capacitor across it. I had no idea what frequency it was "tuned to".
> There
> was no SPACE filter in the TU at that time. I had no problem copying RTTY
> on one tone. I eventually moved up to "TV Width Coils" and
> eventually 88 mHy toroids.  I had the benefit of living on Long Island (NY)
> which was the home of several commercial press RTTY stations. So their
> signals just boomed in, day and night. The old Model 26 got a real workout.
> I was even able to copy the hilarious propaganda broadcasts from
> Korea.
>
> The ARRL published a single-tone RTTY "TU" circuit in the ARRL Handbook
> for a few years. But I doubt it was very effective when RTTY and CW
> was hot and heavy on the lowbands.
>
> I moved from the Twin Cities TU to the Mainline TT/L-2 when I got serious
> about actually transmitting on RTTY.
>
> Jack K2TTY
>
> NNNN
>
>
>
> -----Original Message-----
> From: greenkeys-bounces at mailman.qth.net
> [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Ralph Mowery
> Sent: Saturday, February 17, 2018 10:18 AM
> To: GreenKeys at mailman.qth.net
> Subject: Re: [GreenKeys] on-off radio teletype (not FSK)
>
> Just like many things, there is usually a trade off.
>
> The wider shift will give a better copy on selective fading, but it takes up
> more band width.  You can use a narrow shift and a more selective filter to
> help keep other signals from causing interference.
>
> I got into rtty too late for the wide shift.  I did build up a st-6 and it
> will copy on either mark or space.  I have watched even the 170 hz shift
> fade from one tone to the other on some occasions.  At one time several of
> us in the local area were copying pix off 20 meters.  I did not have a very
> good receiver or antenna, but could usually copy better than those that had
> the st-4 and other demodulators that needed both tones to copy rtty when the
> band was not in good condition.
>
>
>
>
> -----Original Message-----
> From: greenkeys-bounces at mailman.qth.net
> [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Robert Downs via
> GreenKeys
> Sent: Saturday, February 17, 2018 12:19 AM
> To: greenkeys at mailman.qth.net
> Subject: Re: [GreenKeys] on-off radio teletype (not FSK)
>
> I would say "less likely" rather than "unlikely" but selective fading was
> why I disagreed with the statement in an earlier post that wide shift was
> found to be unsatisfactory on HF but narrow shift worked just fine.  With a
> converter capable of copying mark-only and space-only you have a frequency
> diversity system that uses only one receiver and one antenna.  It would
> probably perform better that a narrow shift system under frequency selective
> fading conditions.
>
> Robert Downs - Houston
> WA5CAB
>
>
> -----Original Message-----
> From: greenkeys-bounces at mailman.qth.net
> [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Jim Haynes
>
> Another reason for 850 Hz shift, realized later, is that the two tones can
> be detected separately and the detector outputs combined, giving the effect
> of frequency diversity.  It was unlikely that both frequencies would fade at
> the same time.
>
>
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