Rick has this right. The early OMNI rigs were not very sensitive on the
low bands but the sensitivity increased with frequency. This is one
very easy explanation for the "quiet" receiver characteristics. I found
that if I added an outboard preselector to the OMNI-C and gave it 15 db
or so, it sounded like most of my other receivers (and correspondingly,
my other receivers with the RF Gain turned down a bunch would sound
about as quiet as the OMNI). Under normal conditions, it was just plain
reasonable to have less sensitivity on the low bands. However, for weak
signals and through serious filtering, the OMNI-C would sometimes not
have quite enough gain for me (couldn't get into any AGC action and weak
signals would barely show up in audio) where my other receivers (namely,
the Kenwood TS 440) could dig weak ones out of the mud with narrow
filtering.
Bear in mind, the 440 would not have a chance if the weak signal was
next to a strong one, the OMNI-C could then move in for the kill.
Receivers are fun.
Clark
WA3JPG
On Wednesday, February 18, 2004, at 02:17 PM, Rick Westerman wrote:
Next, at the risk of being accused of "making this stuff up", I'm
goint to rely on my old gray cells to state something I "think" I
remember. It is a known fact that the rigs need more sensitivity
on the higher bands and less on the lower bands. I seem to
remember that Ten-Tec, back in the 80's used to actually build
the rigs to accomadate that, whereas the Japanese vendors seemed
to strive for unity gain (sensitivity), which resulted in their
rigs needing attenuation up front. The Ten-Tecs didn't need it.
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