From: Jim Brown <jim@audiosystemsgroup.com>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] 1dB more RF Power?
On 5/7/2020 10:15 AM, Jim Thomson wrote:
> Hundreds of tests have been run, with ssb signals right at the
> noise level,
> or slightly above the noise level. And in every case, increasing
> the top end
> improves speech intelligibility by a HUGE amount.
<Of course. And in speech reinforcement systems, we carry response up to
<at least 10 kHz. BUT my advice is for weak signal communications
<circuits for DXing and contesting. Band congestion is extreme during
<both of these conditions, so the use of ESSB is out of the question for
<these times.
> Microphone is a RE-27.
<That's a fine microphone. I own several, also RE20s, which I use for
<recording music. They are my first choice for trombone, and for tenor
<and baritone saxophones. It is massive overkill for ham radio, and it's
<a relatively flat mic, so it lacks the built-in boost around 3 kHz that
<good communications mics provide.
<73, Jim K9YC
## forget contesting. But for dx use, essb works superb into EU/south
pacific/
SA/JA and everywhere else..all bands too, including 80m. ESSB usually
takes place where
congestion /qrm is not present, or BW minimized to deal with it. IE:
4 khz vs 5 khz.
## Check the response curve on a RE-27..its not flat, it rises. RE-27
has 2 x built in bass roll off freqs.
2nd one rolls off below 1 khz. With 2nd filter on,
the response almost looks sorta like a pre emphasis curve. Moot point,
since I EQ it for my tastes..and dont normally use either filter. An
ideal, optimized EQ setup only works for
one mic and one operator. Local buddy jumps into my chair, and eq is
all wrong for
his voice....and vice versa when I visit his station 1 mile away.
## Local ham buddy, his bro in law runs a recording studio across
town. A myriad
of condenser mics and avalon pre-amps, daws etc, etc. He uses the
RE-20 for saxaphone,
its superb.
## I have had minimal to zero success with... communication
microphones. I and others can hear the
distortion in them asap, vs a RE-20, RE-27, MD-421, SM-7, various popular
condenser mics etc. Its like
a layer of..gunge. Apparently its the IM distortion from the lower
quality mics. Its not some subtle difference
either, its blatantly obvious...apples and oranges.
## To pull all this off, I cant use the junk mic pre-amp on my
yaesus. Audio is fed directly..via a 20 db pad, then jensen xfmr
into the analog BM..via a 220 uf, non polarized, panasonic coupling cap.
Bill whitlock was adamant
about that at the time. With no coupling cap installed, the BM is
instantly unbalanced, resulting in CXR present.
Output of cap is wired directly to the correct pin on the analog BM
chip. Audio comes in the rear on a new chassis
mounted rca connector..... so no pin 1 issues.
## similar deal on RX. Output of analog product detector is routed to
yet another newly installed RCA chassis connector,
where it is amplified externally... ( 2nd channel of my rack mount mic
pre-amp)..then into a class A headphone amp setup.
If driving speakers, its fed into the turntable input on my external
stereo pre-amp. But the RIAA circuit is 1st removed,so
no de-emphasis takes place. Yaesu 1.5 watt audio amp and headphone
amp is junk, we cant use it. Headphones are
either sennheiser HD-250s, or sometimes the boom-mic version..,.or
sennheiser HD-650s. Thats about as good as I can get it.
The 650s are superb, they let your ears breathe. The 250s seal out
noise, but are like wearing ear muffs.
## Does your elecraft K3 rx or tx beyond 3 khz ?? If not on RX,
you have no way
to evaluate the mode. 2.4 khz audio is fatiguing, I dont miss it. I
dont miss not having to use phonetics either.
Jim VE7RF
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