Date: Fri, 1 May 2020 00:35:18 -0700
From: Jim Brown <jim@audiosystemsgroup.com>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] 1dB more RF Power?
<Absolutely. When the signal is close to the noise, small differences in
<the level of the signal become VERY important. And those half and single
<dB add up. 1 dB from bigger coax or hard line, more/longer radials for a
<vertical, raise a 40M dipole by 5 ft, or an 80M dipole by 10 ft, or turn
<an inverted vee into flat dipole at the same height. Three of those 1 dB
<changes combine for 3 dB (equivalent to doubling the TX power.
#### N6BT is adamant that a rotary dipole has 6 db more gain vs an
inverted vee, with the apex of the inverted vee at the same height
as the dipole. In my experience, an inverted vee is an omni directional
ant..and thats with a good CM choke used at the feedpoint. A rotary
dipole has a 14 db FS ratio..and will eat an inverted vee for lunch.
<On SSB, we can increase our loudness on the other end with EQ and
<amplitude compression. Rolling off everything below 500 Hz adds 3 dB;
<amplitude compression set for 10 dB on voice peaks adds that 10 dB. That
<13 dB is equivalent to multiplying TX power by 200!
<73, Jim K9YC
## Nonsense. Rolling off everything below 500hz is fubar. It will
...and does, sound like a tin can. Ditto with rolling everything off
below 400 hz. A gradual roll off below say 350 hz.... followed
by a pronounced, steeper roll off below 300 hz works good.
As does a steep roll off below 300-325 hz. But the rest of the
pass band has to be very carefully equalized. This is where
multi band, digital parametric EQ shines. Then the eq can
be dialed up, dead on, and optimized for the application..
...albeit, a lengthy process. Then add the compression.
If you really want to go crazy, multiband digital compressors
can be used. End result is a helluva lot louder..without any
inband distortion products, like what is heard when RF clipping
is employed. Same concept as used by TV broadcast. Commercials
have 6 db more average power vs normal program material...
with zero distortion.
## I looked at TV audio on my spectrum analyzer, both channels
and full BW....and when the commercials come on, all the peaks
dropped exactly .5 db. Meanwhile the average power increased
by exactly 6.0 db. I could simultaneously measure both peak and
average... in
.1 db increments. For ham use, the compression is typ increased more
than 6db.
## since experimenting with ESSB mode since 2001, we all
noticed asap, that by extending the top end to 3800- 3900 hz,
phonetics
are no longer required..or used. Even with signals buried into
a noisy 75m band, phonetics are never used. It gets even better
with top end higher than 4000 hz. The drawback of course is
wider bandwidths are more prone to QRM.
## We have run hundred of tests, and I have several mini disc
recordings of stations slowly incrementing their top end in
100 hz increments, starting at 2700 hz....then 2800 hz...etc,
etc, up to 3900 hz...and higher...up to aprx 4500 hz. The
results flabbergasts me every time I play that series of recordings.
The theory is... with top end limited to say 2800 hz.... all the
consonants get..crushed. And this is with signals at or just above
the noise level. The improvement in intelligibility is astounding.
This is all old news, since collins engineers already went through this
in extreme detail, as depicted in SSB systems + circuits.
Jim VE7RF
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