What we encountered were dynamic range problems. The instrument operates as
HP says, but if a strong enough interfering signal appears at an input, it
overloads the first(usually) active device, causing various unwanted
products to appear in band, and sometimes desensitizing the channel. Urban
problem with many other radio services nearby, and it doesn't help to be
under the landing path of USAF aircraft with their jammers still active
either.

--
Crazy George
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