[600MRG] Bad news / help request

[Murray Greenman]

Paul,
Here's what I use:

     
https://www.qsl.net/z/zl1bpu/PROJ/MF%20Transmitter/MF%20Transverter.htm

This describes a simple transverter and 100 W power amp for 630 metres 
(but could equally be for 2200 metres). At present I use a TCXO at 10 
MHz to convert down from an old marine transceiver with an OCXO 
reference (Kenwood TKM-707), running on 30 metres.

For extreme stability you could use a transverter like this with a GPSDO 
as the 10 MHz source, or perhaps a rubidium source such as the Frequency 
Electronics FE-5680A. But you'd also need to lock the transceiver.

For transmit only, it's also possible to use a DDS synthesiser directly, 
with just a power amplifier (such as the one described above). You would 
need to write some code to control it in JT9, but that's not impossible. 
I've already done it for WSPR and other modes for a serial programmed 
FE-5680A. You would need to lock the DDS synthesiser to a GPSDO or RB 
source. Serially programmed FE-5680s are now really hard to find, but 
can be programmed to within 10 milliHz and quite fast enough to send 
JT9. Never worry about drift again!

If your strengths are in software rather than hardware, commercial DDS 
synthesisers such as the Novatek 409B can be serially programmed AND 
locked to a 10 MHz source.

The problem with transverters is that the errors ADD even when the 
frequencies subtract, so two 0.1 ppm sources at ~10 MHz result in a 630 
metre signal that's just 4 ppm! You need both the mix down source and 
the transceiver to be 1 ppb stable. Direct generation on 630 metres 
using an Rb or GPS referenced synthesiser is much the easiest solution.

73,
Murray ZL1BPU