To the contrary:
1) Measuring IP3 is a good indication of how a receiver handles strong
interfering adjacent frequency signals. Checking at a variety of
spacings can show up more receiver design faults than simply depending
on one number at 20 KHz spacing.
2) AGC doesn't help when the intermod from signals outside the desired
pass band modulate the AGC and the desired signal. AGC on the RF stage
can hide the weak signal in the noise if the AGC is created from the
unwanted strong signal.
3) Filtering does best as close to the antenna as possible. Many pacific
rim receivers have forgotten that detail and use a wide first IF filter
without beefing up the second mixer and so the intermod falls apart for
closely spaced signals.
4) Ten Tec receivers do quite well, especially the Corsair and Corsair
II in both measurements and performance. They don't demand unlimited
budgets.
73, Jerry, K0CQ
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Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.
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