> It's amazing, but I really think most of our s meters are
> miscalibrated and the strongest signals tend to be more
> like s9+20 and not s9+40 as our meters tend
> to read. Anyway, I find it extremely rare when the 40 db range
> is not enough for the close in stuff.
Let's see. Most manufacturers today say they have set up
their S meters to read S9 when 50 microvolts appears at the
rigs input antenna terminal. Add 40 dB to that voltage,
and you find that 5 millivolts is now at the terminal (100
times voltage increase, or a rcv'd power increase of
10,000 times!!!).
Living out here on an island near mid-Pacific, I know I have
NEVER rcvd a signal of a strength of 9 + 40 dB on the amateur
bands. From some of the other islands, from 120 to 350 miles
away, from stations running full 1500 watts, more like 9 + 15 or
maybe even on occasion, +20 dB; from the rest of the world,
not a chance.
Now, what is the probable dynamic range among stations
within the San Francisco Bay area, or Los Angeles County on
160 meters during the 160 contest or other metropolitan
area during any of the major contest weekends compared
to the incoming desired signals from far away places??
Well, rambling. Wonder how the AGC action is distributed
between the analog and DSP stages in these new rigs?
I know the 340 has 80 dB of IF gain in the analog stages,
and another 40 dB of gain available from the DSP. Is the
AGC first applied to the analog stages, or some to each?
When I cut the IF gain (by reducing the Manual RF gain
control setting), am I lowering only analog stage gain,
DSP, or some of each...wonder how Ten Tec did it in
the 340. Manual does not say.
When having afternoon QSO's with other Hawaiian stations
out here, I always have the IF gain cut around 45 or so dB,
and the 10 dB gain RF preamp OFF. These settings eliminate
the usual Spanish language QRM we experience on 40 meters
out here in the late afternoons arriving from Central and
South America. The 340 AGC action is such that I can
perceive no decrease at all in the "loudness" of the audio
during the net with lowered RF and IF gains from that heard
with everything full ON. Note that the S meter of the 340,
driven by the processor does NOT change reading with
either preamp condition nor IF gain setting deltas. Very
interesting.
73, Jim KH7M
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