Re: Technical question on keying of an SDR radio

Posted by Elecraft mailing list on Apr 08, 2019; 3:07pm
URL: http://elecraft.85.s1.nabble.com/Technical-question-on-keying-of-an-SDR-radio-tp7650719p7650734.html

Wayne,

Thanks for the explanation.  I should have realized that it might have been documented.

My question was prompted by the appearance of a question posted to the "ham radio" formum of Stack Exhange on-line.  The OP (original post) of the question mentioned looking at a 1976 ARRL Handbook and seeing a circuit for the keying and wanted an explanation of how that circuit worked.  The answers (at the time I read the post) were somewhat simplistic and directed to the circuit that was shown in the question which of course was technology going back to the 1940s or before.  

Thus, I was curious of the improvements possible with DSP.

Thanks,
phil, K7PEH

> On Apr 7, 2019, at 10:25 PM, Wayne Burdick <[hidden email]> wrote:
>
> By the way, a similar explanation can be found in the Theory of Operation section of any of our transceiver manuals.
>
> Wayne
> N6KR
>
>
>> On Apr 7, 2019, at 9:58 PM, Phil Hystad via Elecraft <[hidden email]> wrote:
>>
>> If you look at various old circuit diagrams of ancient radios made from electronic circuits you find that the telegraph keying for the radio involves switching on and off the driving oscillator frequency or something similar.
>>
>> However, with an SDR, you have other options and I have no idea how it is typically done.  For example, a digital signal can be produced that represents the Morse coding and this signal need merely be converted to analog and amplified.  Or, is there still an analog circuit being switched on and off for Morse code (telegraphy) keying with a modern SDR.
>>
>> Can someone describe how this is done in a radio like the KX2.  And, is it done differently in the different Elecraft radios — I presume that the K2 would have the more traditional sort of circuit but that is really just a wild guess on my part.
>>
>> 73, phil, K7PEH
>

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