Craig says:
> Military receivers of the late 1980s had intercept points of
around +30dbm
Receiver intercept point isn't everything. Unless the phase noise limited
dynamic range and the intermodulation limited dynamic range are
approximately equal, you can't get optimum performance. (see my IEE paper in
1996) Measurements suggest that in reality the SFDR required at HF is about
100dB mark, but the start point needs to be variable. This means that when
the really big signals are there that cause IMD difficulties, the noise
floor at the antenna is higher too, so an antenna attenuator can be a useful
tool. I alway used to think that it indicated an inability to design the
front end, but that's not necessarily so. See also the paper by Barrs, 'A
re-appraisal of H. F. Receiver Selectivity' IERE Conference publication No.
50, ISBN 0 903 748 45 2. A 100dB SFDR requires at least a -134dBc/Hz
phase noise performance to be useful. It also needs that in the transmitter,
too!
73
Peter G3RZP
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