LF,

This is now working! I used the QRP 2000 synthesiser (completed with assistance 
from G8DQX) and have added a divide-by-100 unit based on the design by G3KAU 
with some modifications:

- the original design assumed 10 to 50 W sine wave input. I left out the 
attenuator because the synthesiser delivers 2.6 V peak to peak square wave, 
which is enough to drive the 4017,

- I was not intending to use anything other than 137 kHz and the power 
amplifier requires square wave drive, so I left out the post-divider filters,

- the output from the second divide-by-10 stage is sufficient to drive my Class 
E Power Amplifier so I didn't bother with a buffer,

- there are several versions of the 4017 but with different capabilities and 
voltage ratings. I used the CD74HC4017,

- and provided a 6 V rail rather than 13.

The unit is now in a die-cast box and I shall shortly be testing it with the PA 
into a dummy load.

After that, I need to look at software for driving the synthesiser.  For test 
purposes I have been using the SI570 programmes referred to in the 
documentation but they clearly are not appropriate for transmission.

Many thanks for all your help and encouragement.

73
John F5VLF