Folks, we aren't trying to crucify any brand or model. Just trying to make
folks be aware that there are things going on with today's radios that are
making for noise on the bands. We need to be mindful that many radios
aren't really "clean" when they transmit. While that doesn't bother the
operator for he's transmitting, but what about the ham a couple of blocks
away? He may be affected by broadband noise when he is on one band the
other station is on another. Or you could be that other ham that has the
noise floor increase when the other station is on the air. You may say
"oh, that's not much" when in fact, it all adds up to increased noise
regardless how miniscule the amount.
Clearly Elecraft took necessary steps to produce a clean transmitter.
Tentec has taken a similar approach. The other brands, Kenwood, ICOM, Yaesu
and some others as examples, seem to care more about sales than our spectrum
environment.
We must realize this fact and act accordingly as well as take some degree of
responsibility toward being a good ham citizen. There is more to it than
ergonomics and features.
73
Bob, K4TAX
----- Original Message -----
From: "Jim Brown" <k9yc@audiosystemsgroup.com>
To: <tentec@contesting.com>
Sent: Sunday, July 06, 2014 3:33 PM
Subject: Re: [TenTec] On Noisy Transmitters
On 7/6/2014 7:07 AM, Rick - DJ0IP / NJ0IP wrote:
Cheap is cheap in more ways than most people realize.
YES! Wayne, N6KR, talked about phase noise and what he did to minimize it.
In a different email (can't find it right now), he talked about what he
did to minimize clicks.
Clicks are generated by rise times that are too fast combined with
intermod distortion. Think of CW as an amplitude modulated carrier, where
the modulation is a square wave. A square wave consists of an infinite
number of harmonics. The faster the rise (and fall) time, the more
harmonics, and the higher order harmonics will be stronger. Those
harmonics, then, interact with IM distortion to produce sidebands. Those
sidebands are the clicks. That analysis is mine.
What Wayne said (I'm paraphrasing) is that he developed optimal shaping
for the square wave that minimizes those harmonics while still providing
nice, distinct keying at high speeds. If I remember correctly, he called
it "sigmoidal," after the mathematical name for the function that he used.
He noted that it takes a lot of DSP cycles to do that, as well as a lot of
programming, and that when you're doing that, there are other things you
cannot do because you've dedicated the DSP to that function.
The point is that Wayne and Eric made the design and marketing decision
that having a very clean TX signal was the highest priority. I don't know
much about the current Ten Tec rigs, but I do know that when Al Kahn was
around, that was also a very high priority for Ten Tec.
73, Jim K9YC
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