[AdrianH]

I think the CODAR design was very novel and quite simple for the time, the fact it was copied by many is testament to the fact it basically worked. I do believe that spurii was not really an issue back then, or at least not really considered in any great depth.

I would need to build a separate VFO on a board to see if I could switch between 160m and 80m and be stable before any attempt to retro fit. One thing I could do is drive it initially with the DDS which I have now found, first I need to see how clean/jitter free that is, then see if it is a cleaner output.

An alternative is to add fixed crystal positions and go for additional 3.615 MHz and a CW spot on 80 as well as the VFO for 160.

Going back to something much earlier in the thread about the modulation, I realised I made a boo boo when I wound the transformer, I wound it symmetrically, i.e. same turns both sides of the centre. This is possibly why I can only reach 75 to 80% mod, I tried the dropping resistor and cap circuit to make up for the fact the mod valve has it's Cathode at 13 to 14 Volts above ground, it gave me a few extra percent, but the original transformer was asymmetrical being originally 110 Volts on one side and 130 Volts on the other, so I should have done one half with more turns. I may try this out to see if it gives me more modulation. The mod valve is drawing between 46 and 50 mA, the PA I am limiting this to 40 mA max and the residual DC level does not seem to be causing any issues!

I am enjoying the build and the whole process, it is still my main way of learning as opposed to just reading texts. I have to have something to relate everything to and try things out.

Adrian