I picked up this receiver today. Some fellow traded it even up with a friend
of mine for an R4C. I traded a Takahashi FS-78 Flourite refractor for it. If
the JRC unit was working properly, it would have been a good deal, but I
thought, "what the heck?"
When I put it on my test bench, it could barely hear a 60% modulated 10uV
signal...........not good.
I did download a schematic from a Dutch website and saw that the 1st mixer
uses U310 JFETs. No big deal, right?
When I removed the shield from the mixer assembly, I discovered that instead
of the U310s, a Siliconix E431 dual JFET is used. This is a very high IP3
mixer, capable of +20 to +30dBm in a properly designed circuit.
I bought a batch of them several years ago from, you guessed
it....................the Rockwell-Collins surplus store.
I replaced the defective component and now the receiver is hearing signals
all the way down to .1uV, which is typical of any of the modern day
receivers that use this topology.
I have been looking for one of these receivers for a few years; it's ironic
that about the only way that you can get ahold of them is if they are in
need of repair. It wasn't too bad..........about an hour or so for the
repair.
Now I see why people don't want to sell these receivers. Good
quality......................even the roofing filter appears to be a 6 or
8-pole unit. This one's a keeper!

Pete