[GreenKeys] Frequency diversity radioteletype experiments

Mon Oct 12 15:49:57 EDT 2026

Interesting!

I think it would be interesting to get some repeatable numbers on various
transmission methods and demodulators.

At
https://w6iwi.org/rtty/audio/#:~:text=spiceaudio220629_2022.wav-,30%20lines%20of%20RY,-%2C%2035%20of%20each
, I have some impaired audio that is 30 lines of RY transmitted from here
and received on the KFS websdr.

Counting the number of Rs received and the number of Ys received gives a
measure of how well a demodulator handles the impaired signal. I have
added an RY count command to the DSP TU ( https://w6iwi.org/rtty/DspTU3/
).

Included in an extensive AI QSO at https://w6iwi.org/rtty/DspTU3/ is a
further discussion of using the RY count method of evaluating
demodulators. It could also be applied to the multitone transmission
method.

The AI QSO starts with a discussion as to why the AEA PK232 does not like
one stop bit. It then goes into the RY count method of evaluating
demodulators. Finally, since we do not really want to count Rs and Ys off
peper, it goes into a loop to USB interface.

There is a ROUGH comparison of TUs at https://w6iwi.org/rtty/TuComparison/
. There, bad lines are counted by hand. But the RY test would, I believe,
be more accurate.

I also just had an AI QSO on backward compatible error correction using
blank/ltrs to carry the error correction bits. It is at
https://share.google/aimode/ulj3X7yojH6biqMDr

Harold
https://w6iwi.org

On Mon, October 12, 2026 11:59 am, Nick England wrote:
> We tested 850Hz shift single channel at the same time and 425/2805
> diversity was definitely better.
>
> Nick England K4NYW
> Chapel Hill NC
> www.navy-radio.com
>
>
> On Mon, Oct 12, 2026 at 1:29â€¯PM Harold Hallikainen via GreenKeys <
> greenkeys at mailman.qth.net> wrote:
>
>> That sounds great! The 2805 Hz is pretty high for an SSB transceiver.
>> Also, it seems that the levels of the simultaneous tones have to be kept
>>  down since their amplitudes add. I wonder how this compares with just
>> running wide shift (say 2 kHz) with dynamic threshold control.
>>
>> I want to experiment some with space diversity. It will not be as fancy
>> as having two receivers and a diversity TU. Instead, I'll just switch
>> antennas whenever the TU is in mark hold. There will be errors, but
>> ideally there will be better copy in a long fade.  A TV satation I
>> worked with did this on a microwave receiver. There were two dishes on
>> the tower. During a fade, they would switch to the other dish.
>>
>>
>> The 8:30 AM ET is a bit early for me being on MST. But I'm almost
>> always on 14.086 MHz LSB (14.083,875 MHz Mark, 14.083,705 Space)
>> autostart during the day.
>>
>> Harold
>> https://w6iwi.org
>>
>>
>>
>> On Mon, October 12, 2026 7:32 am, Nick England via GreenKeys wrote:
>>
>>> Ron K3TZJ, John K9WT, and I had very nice QSO/test session last week
>>> and today using the MD-522 diversity mode for radioteletype. It worked
>>> very well indeed at overcoming fading and QRM. This mode sends
>>> identical 85 Hz shift tones centered at 425Hz and 2805Hz. Come join us
>>> or listen in. Monday 0930 EDT. 7087kHz USB. Mark low. 45 baud.
>>>
>>>
>>>
>>> And donÃ¢â‚¬â„¢t forget our regular Saturday morning 850 shift net
>>> starting around 0830 EDT also on 7087 USB (2000 Hz center). A couple
>>> of the
>> fellows
>>> have used spatial diversity for receiving on that net, with two
>>> different antenna/receiver channels feeding a diversity combiner TU.
>>>
>>> Remember, if you don't have a short wave receiver that you can always
>>>  listen in via web SDR http://www.websdr.org/
>>> http://kiwisdr.com/public/
>>>
>>>
>>>
>>> Have fun,
>>> Nick England K4NYW
>>> Chapel Hill NC
>>> www.navy-radio.com
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>>>>>
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>>
>>>>> 2002-to-present greenkeys archive:
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