I recently fitted the Kuhne IF transverter modification board and found I had some issues with it.
When I first fitted the board I had a strange pulse appear on receive when using the transverter I original put this down to having to much signal going from the transverter to the rig and so switched on the rigs attenuator to resolve the issue. Now I didn't do this in a very scientific manner I just put the attenuation in on gut feeling.
Next I noticed when using my Wavenode power meter when I de-keyed the transmitter I had a 1.3W RF spike out of the transverter which resulted in a 200W spike from the linear. After pulling the system apart in an effort to resolve the issue I discovered the cause was the Kuhne modification.
As I found the issue with the Wavenode was caused by the interface board I had another look at the RF pulse I was seeing without the rigs attenuator turned on. I tuned in the GB3VHF beacon which appeared as S9 on the S meter while using the transverter with the combiner and then switch back to IF interface where GB3VHF stayed at S9 without the rigs attenuator turn on however the pulse was present again so I again switched the attenuator back on resulting in the beacon losing an S point but the pulse had disappeared.
I did a quick search on the internet and found on the IC7300 io.groups reflector a PDF documenting a modification to do with instabilities found with the IC7300 power amplifier when the Kuhne board was disengaged and carried out the modifications which made no difference to my problems which in all honestly wasn't surprising.
I've now decided to remove the modification and go back to the combiner and attenuator method of driving the transverter which was far more stable and had no issues.
Another observation is the fact I kept seeing some IM products in the adjacent 3kHz from where I was operating from which I just couldn't get rid of it wasn't bad about -25dB in relation to output and wasn't always present but with the modification removed it vanished completely to the point where any IM product is now at least -35db at worst.
