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[Amps] 440s current/IMD

To: <amps@contesting.com>
Subject: [Amps] 440s current/IMD
From: craigs99@iprimus.com.au (craig)
Date: Sat, 28 Dec 2002 16:35:42 +1100
I would be interested in this information too. With the current batch of
transceivers its getting hard to find a model with good transmitter IMD. In
fact the IMD figures seems to be getting worst.

The older model radios like the IC765, FT1000D, JRC 545 all have superb 3rd
order IMD figures all over -35db. Likewise the 5th order IMD numbers are
very good. Looking at the recent ARRL reviews there is very little
difference between the cheapest radios and the top range models. We may have
to collect these older cleaner radios if you want a clean drive signal.

Considering the noise levels on the bands I wonder what the minimum
acceptable  3rd order IMD would be?. The ARRL references its measurement to
PEP and most of the commercial gear is reference to 1 of two tones. This
would make -36 db the minmum, such transceiver are rare in the ham radio
market.

The VHF contest operators seem to pursue the best close and far out IMD
performance which is quite stringent. Of coarse not everyone is so
considerate in this regard. HF is no different most people who seem to
splatter don't care. Although these days i frequently only seem to hear bad
signals with those stations running IC706's into amplifiers, the distortion
is quite easily detected. The other bad splattering stations are well beyond
help and seem to be beyond help or wanting to accept "constructive
criticism"  The attitude that "i payed 10 grand and dont splatter" seems to
predominate with these recalcitrant stations.

Craig
VK3HE


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