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Re: [TenTec] On Noisy Transmitters

To: <k9yc@arrl.net>, "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Subject: Re: [TenTec] On Noisy Transmitters
From: "Bob McGraw - K4TAX" <RMcGraw@Blomand.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sun, 6 Jul 2014 20:33:50 -0500
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
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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