[GreenKeys] Range Finder Setting/Distortion usage?

Mon Feb 6 17:45:45 EST 2023

My theory is that an ASR can have things like an aux reperf and who-knows-what-else in it, so they thought it best to have a local loop supply, lest they bog-down the external supply with too many widgets in the cabinet. Whereas the KSR doesn't have other gadgets and can be driven right from the external loop. Just my thoughts on the matter. 

Right now, I am using an ST-6 for a loop supply (and also for 170 shift) but mine is of the newer ilk that doesn't have a rheostat, only a fixed power resistor. I now find my loop running at about 50mA due to a lot of devices on the loop. 

73 Eugene W2HX
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-----Original Message-----
From: greenkeys-bounces at mailman.qth.net <greenkeys-bounces at mailman.qth.net> On Behalf Of John W9DDD
Sent: Sunday, February 5, 2023 10:22 PM
To: harold at w6iwi.org
Cc: greenkeys at mailman.qth.net
Subject: Re: [GreenKeys] Range Finder Setting/Distortion usage?

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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>>> Jordan Spencer Cunningham's GreenKeys Search Tool: 
>>> https://teletype.net/gksearch 2002-to-present greenkeys archive: 
>>> http://mailman.qth.net/pipermail/greenkeys/
>>> 1998-to-2001 greenkeys archive: 
>>> http://mailman.qth.net/archive/greenkeys/greenkeys.html
>>> Randy Guttery's 2001-to-2009 GreenKeys Search Tool: 
>>> http://comcents.com/tty/greenkeyssearch.html

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