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
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