No, it doesn't help!
It is true if everybody would be using Inverted Vee antenna in a city
environment on low bands. The lower you go on frequency, the more noise you
encounter
(you "don't need sensitivity"). But take that receiver to the ocean front,
put directional antennas on it, use specialized receiving antennas and you will
find that you NEED gain on low bands. Or beaming with good directional antenna
north, away from the equatorial noise and try to dig those 10 W JA novices.
You can use every uV you can scramble.
Designers telling us that we do not this or that are flying in their
imaginary "realities". Good receiver should have maximum sensitivity on all
bands -
that has CONTINUOUSLY adjustable RF gain (not a step dB attenuator or preamp)
so
we can set the noise from the band right at the threshold. It is up to us to
either use max with specialized antennas, or turn it back on noise pickers. RF
and IF gain should be separate controls.
Example what I had to do back in Drake B line days. I modified my R4B by
changing the preselector tube to EF183 (6EH7 ?), put separate RF gain control
in
the cathode circuit, left the AGC and "RF" (really IF gain) to be applied to
the grid. I gained about 20 dB amplification that I had available either for
shorter Beverages, small loops or on 10m when beaming North. No need for
external
preamps, tuned input and output. With riding the RF gain to keep the band
noise at the threshold, having IF gain (adjustable too) set to current
comfortable level, and 600Hz roofing filter with following LC 2nd IF, this RX
is still
on the top. S-meter would sit at 0 regardless of "RF" gain setting. This and
continuously adjustable AGC is missing from all the "modern" receivers,
transceivers.
Making receiver less sensitive on low bands so you can claim "it is sooo
quiet" is ridiculous. (Just like W4PA telling us we don't need PTT on CW.) So
one
should be suspicious about "quiet" receiver as well as noisy one when you
short the antenna terminals. If you can't hear it, you don't know what you are
missing. If you are a contester, this is the difference between winning and
ending up further down. You win contests by working those that others can't.
Yuri, K3BU
In a message dated 2/24/04 4:55:03 PM Eastern Standard Time,
w1ael@mindspring.com writes:
Temporarily disconnect the antenna and set RF Gain on MAX. Turn up
audio to a convenient level of noise output. Now restore the antenna
connection. On a receiver with sufficient sensitivity for HF, the audio
output noise level will increase (quite a lot on 80 meters!). You have
just demonstrated that the receiver hears the external noise well above
its internal noise. It will be IMPOSSIBLE to hear any signal lower than
the external noise. Jupiter will easily pass this test, as should the
746 PRO. Make your choice based on some factor other than sensitivity!
This is not some theory-in-the-clouds notion, but a time-honored
practical test with solid theoretical underpinning.
Hope this helps,
73 de W1AEL (retired from Ten-Tec engineering)
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