[R-390] Interesting Radio

[Charles Steinmetz]

>  http://huntsville.craigslist.org/ [etc.]

Why do some of these myths persist?  We have good, reliable test data 
on dozens to hundreds of receivers, which clearly show that many of 
the often-repeated claims about the 390A are ... well, let's just say 
... exaggerated.

"The R390A/URR communications receiver also happens to be one of the 
quietest receivers if not the quietest ever built. It is capable of 
copying AM and CW signals all the way down to its -143db noise floor, 
all while maintaining the ability to operate in very strong and 
overloading signal environments and strong signal conditions..."

That is just not true.  It's a great receiver, but the noise is (at 
best) 6dB worse than that (most examples give up another 5-10dB, or 
more, as you find them because the IF gain is set improperly), and 
the first mixer overloads way too early, making the overload and 
dynamic range performance far inferior to a great many other 
receivers.  According to Rob Sherwood (and consistent with my 
measurements of properly operating 390As over nearly 4 decades), the 
390A has a 20kHz (spacing) dynamic range of ~ 81dB, and a 2kHz 
(spacing) DR of ~ 79 dB, with a noise floor of -137dBm and 100kHz 
blocking of 130dB.  Robust, high-DR commercial receivers have wide 
and narrow DRs in the 105-110dB range (that is, 25 or 30 dB better 
than the 390A) and blocking in the 140-155dB range (that is, 10-25dB 
better than the 390A).  State-of-the-art single-band receivers can do 
another 15dB better than these figures.

"Each major area of the receiver is contained in easily removable 
subassemblies..."

Oh, come on.  "Easily removable subassemblies???"  I want some of the 
mushrooms he's eating....

Finally, "It was widely used in Desert Storm, when many of the newer 
solid state receivers would not function reliably."

Does anyone here have actual, documented (i.e., NOT anecdotal, "my 
cousin was there and he said...") data on this?  I wouldn't be 
surprised if a few were used here and there (particularly in some of 
our ships that haven't had their HF comms upgraded in decades), but 
I'd be extremely surprised if they were deployed to any extent that 
could even remotely be called "widely."


Best regards,

Charles