[600MRG] Interesting article in QEX

[Brian Pease]

I think that the QEX design could likely be redesigned for 630m but it 
would take some effort.

I have used an Elecraft K3S for years in transverter mode to receive 
630m WSPR and provide 1mw (max) drive to a homebrew 100W P-P Class-E 
power amp.

I am changing from the K3S to another transceiver that does not have 
630m transmit capability.

I have modified a QRP=Labs QDX-M single band digital-mode-only 
transceiver (no CW!) to work on 630m. It has very good receive 
capability. I don't need the power amp in the QDX so I left out all of 
the amp parts. I used just a series resistor and blocking cap to obtain 
200mv p-p square wave drive into 50 Ohms from the 5V gate drive, which 
is plenty for my 100W amp. The QDX connects to a laptop running WSJT-X 
via a USB cable that has both audio and CAT control like any modern radio.

The QDX firmware is already set up to recognize 2200m and 630m but there 
are no parts kits (yet!) to run the radios on these bands. The TCXO in 
the QDX is accurate and more than stable enough for the slow digi modes.

It would be easy to configure the QDX RF amp to run as much as 8-10 
Watts in Class-E on 630m which should drive most amplifiers.

Right now I am having trouble with the transmit audio drive from WSJT-X, 
which drops below the level needed by the QDX after a couple of seconds. 
Another QDX behaves the same, and both work fine on an Android tablet 
running different software. Maybe my laptop has a problem?

On 5/6/2025 6:34 PM, Jim Miller wrote:
> In the latest QEX posted by ARRL online there is a modular WSPR 
> transmitter article. Anyone have an idea how this might be applied to 
> something for 630m?
>
> Thanks
>
> jim ab3cv
>
> ______________________________________________________________
> 600MRG mailing list
> Home:http://mailman.qth.net/mailman/listinfo/600mrg
> Help:http://mailman.qth.net/mmfaq.htm
> Post:mailto:600MRG at mailman.qth.net
>
> This list hosted by:https://www.qsl.net
> Please help support this email list:https://www.qsl.net/donate.html
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/600mrg/attachments/20250506/a38f84cd/attachment.html>