[GreenKeys] Range Finder Setting/Distortion usage?

[Harold Hallikainen]

On Sun, February 5, 2023 7:32 pm, Jim Cooper wrote:
> On 6 Feb 2023 at 1:56, W2HX wrote:
>
>>
>> I wonder... the ASR (which seems
>> less accurate than the KSR) has an
>> internal loop supply and relay to
>> key the page printer. This relay also
>> has a bias adjustment. I have that
>> adjustment at 30mA as per some notes
>> from the guy I bought it from. Could
>> this bias current in the ASR play a
>> part in these two machines behaving
>> slightly differently? If so, then I
>> can play around with adjusting the
>> bias current on the ASR (I guess I
>> could play with it regardless, but
>> thought I'd get the skinny from the
>> experts who know.
>
> That could definitely explain the 'skew' to
> the higher numbers ...  imo
>
> w2jc
>

I agree. I've always wondered why a polar relay is used if a polar line is
not being used. It seems to add more complexity and more things to go
wrong. MAYBE the polar relay and internal loop supply can be bypassed and
just have the loop and terminal unit drive the selector magnets directly.
Failing that, I'd try to adjust the polar relay such that there is no bias
coming out of it. If possible to sample the loop current after the polar
relay, then adjust the polar relay so both mark and space on RY are 22 ms
long. Ideally a test signal would be available with a 22 ms stop bit
instead of the usual 31 ms. That makes it easier to see on a scope since
every bit is the same length. Also, if all alternating bits are the same
length, the average current on a slow moving meter would be 30 mA.
However, since there are 5 data bits, start is space, and stop is mark,
even with a 22 ms stop bit, getting a 50% duty cycle with an R or Y is not
possible. I did create some audio with random 22 ms bits at
https://w6iwi.org/rtty/audio/ for DSP TU testing (generating the eye
diagrams at https://w6iwi.org/rtty/DspTU/ .

In general, I think the ideal design has zero parts, and a polar relay
that is not converting a polar circuit to a neutral circuit is not heading
us towards the ideal design.

Good luck!

Harold
https://w6iwi.org