[GreenKeys] Affordable current loop adapter

[John, W9DDD]

It's been tested with a 28.


On 5/18/2025 8:21 AM, Jeffrey Golas wrote:
> I believe he said the model 15 one depends on the actual 25 selector 
> coils so it wont work with others except maybe a 14.
>
> The 33 one may work but Its prob hard wired for 110 baud?
>
> A 20ma current loop transmitter may work if you can find a way to feed 
> it data, say from fldigi.
>
> The fastest cheapest easiest test would be the arduino one on Hackaday 
> using a relay. It works!
>
> I think this one: https://hackaday.io/project/2836-arduino-teletype
>
> Jeff
>
>
>
>> On May 18, 2025, at 8:19 AM, John, W9DDD <w9ddd at tapr.org> wrote:
>>
>> 
>>
>> Actually the M15 adapter would be a better fit.  Same designer, same 
>> source.
>>
>>
>> https://deramp.com/model15_interface.html
>>
>>
>> Tested on one of my 28s by Mike, don't know whey I didn't think of it 
>> when the question was originally posted.
>>
>>
>> On 5/18/2025 2:20 AM, Erik Grant wrote:
>>> While this one is for the M33, it might be worth while to contact 
>>> this guy @ https://deramp.com/tty_adapter.html 
>>> <https://deramp.com/tty_adapter.html>
>>> Teletype RS-232 Adapter - DeRamp.com 
>>> <https://deramp.com/tty_adapter.html>
>>> The Teletype RS-232 adapter comes fully assembled and tested as 
>>> shown in the pictures on this page. A telephone cord and modular 
>>> DB-25 connector are not included.Version "B" of the board is now 
>>> shipping.
>>> deramp.com
>>>
>>>
>>> ~KF7WAI
>>>
>>> ------------------------------------------------------------------------
>>> *From:* greenkeys-bounces at mailman.qth.net 
>>> <greenkeys-bounces at mailman.qth.net> on behalf of Tim McNerney 
>>> <mc at media.mit.edu>
>>> *Sent:* Thursday, May 8, 2025 9:52 AM
>>> *To:* greenkeys at mailman.qth.net <greenkeys at mailman.qth.net>
>>> *Subject:* [GreenKeys] Affordable current loop adapter
>>> I need to test my 28RO.
>>> Most of the RS-232 to 20 mA current-loop adapters are "wicked 
>>> expensive."
>>> Plus nowadays, RS-232 is not exactly easy to find as an interface.
>>> So I'll be up to $200 before I finally connect to a computer via USB.
>>> And of course USB to current-loop... good luck finding that adapter...
>>>
>>> Can anyone recommend a circuit for a simple 20 mA current loop 
>>> transmitter?
>>> I have EE and soldering chops.  Happy to build my own prototype.
>>>
>>> BTW, I've noticed lots of affordable 4-20 mA current loop transmitters
>>> for remote industrial sensors.
>>> Can these be adapted to serve as a 20 mA digital transmitter?
>>> Intuition makes me think yes, but I want to double-check.
>>> Maybe 4 mA does not equal "0".
>>>
>>> Thanks.
>>> --Tim McNerney
>>>
>>>
>>>
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>> -- 
>> ---
>> ----
>> The above comments or recommendations are SWAG. Use at your own risk.
>>
>> John, W9DDD
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>>>>> Jordan Spencer Cunningham's GreenKeys Search Tool: 
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>>
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-- 
---
----
The above comments or recommendations are SWAG. Use at your own risk.

John, W9DDD