[GreenKeys] Range Finder Setting/Distortion usage?

[John W9DDD]

2874WD and 2875WD show a 28 KSR without line (polar) relay.  I have not yet found a diagram for an ASR without the line relay, but when I do, my ASR will also be without the relay. 

John, W9DDD


> On Feb 5, 2023, at 8:47 PM, Harold Hallikainen via GreenKeys <greenkeys at mailman.qth.net> wrote:
> 
> 
> 
>> 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
> 
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