Message received, thanks! Sorry it is giving you more work to do... I have sent the info + some additional reports as you directed.
On another subject entirely, I finally got around to working on my go-to HiFER receiver. This is a trusty Icom IC_R72 which is generally a very good radio, if simplified over the R71 - it lacks IF shift, for example. However I have found it to be stable, sensitive and selective. Specific to HiFER work, my example developed a quirk which manifested itself as an unstable, and sometimes strong spurious signal. This would be quite dependent on temperature and warmup time, and would also make random jumps, sometimes interfering with monitoring, other times not, but generally, always falling somewhere in the ISM band.
It took some time studying the pages of complex schematic, and chasing the signal around using a sniffer coil connected to another radio, but eventually the source was located - a ceramic resonator of nominal 4.19 MHz - the CPU clock. At first, it seemed that cleaning and tightening some chassis connections between the PCB and receiver chassis helped, but the signal was still there, sporadically. It was strange that the spurious signal was not an exact multiple of the resonator's nominal frequency, even allowing for tolerances, which are quite wide compared to a crystal. That made me wonder if the component was faulty - I have had examples of bad ceramic filters in other radios. At least, the clock oscillatior was definitely the source, because even warmth from a fingertip would make the spurious signal drift significantly.
The auction site scared up a pack of drop-in replacement resonators at very reasonable cost, and here things lay stalled for a while, as I was nervous about how far it was required to dig into the radio and the risk of damaging CMOS logic. Today I plucked up courage and swapped out the part. Casework removed, power supply disconnected and the PSU chassis removed. Processor/PLL board detached from the chassis, but not completely disconnected, and then I had to open a screening can to access and replace the resonator.. then reverse all that, hoping I hadn't "bricked" the radio somehow.
To considerable relief and delight, the set powered up again, having even remembered the last used frequency. Better still, a wide sweep of the troubled frequency range showed no sign of the previous trouble - all quiet on the ISM front.
Cheers
Ed KO6BLM