[TenTec] TX EQ = -14 dB for PSK31

[Ron Castro]

An ALC won't introduce any more sidebands to PSK-31 signal than the amount 
of sidebands it would add to a CW signal in the form of additional key 
clicks over and above those caused by the initial generation of the pulse. 
While this is a problem on radios like the older FT-1000 MKV's, it has never 
been reported as a problem with TT and specifically with Orions.  In fact, 
the Orions seem to have just the opposite problem: a fairly slow-acting ALC.

      Ron N6IE
 www.N6IE.com
(Formerly N6AHA)

----- Original Message ----- 
From: "Merle Bone" <merlebone at charter.net>
To: <tentec at contesting.com>
Sent: Friday, December 29, 2006 5:40 PM
Subject: Re: [TenTec] TX EQ = -14 dB for PSK31


> Ron Castro (N6IE) said:
> "Since PSK-31 works by shifting phase, the amplitude variations caused by 
> ALC
> shouldn't have any significant effect on either the IMD or readability of
> this signal."
> ------------------------------------------------------------------------------------------------------------------------
> Ron, we are going to have to disagree on this one. Anytime you introduce a 
> nonlinearity into the system producing PSK31 signals you will generate 
> unintended sidebands. You may do that by overdriving the audio stage or 
> the PA , or you can do that by introducing any nonlinearity into the RF 
> amplifiers, including the final stage.   Certainly, massively overdriving 
> the signal, as you described, is one way to cause a problem. Of course, 
> using speech processing - which introduces distortion into the signal, - 
> will also cause serious sideband distortion and excessively wide signals. 
> The problems caused by ALC making the final non-linear is probably a 
> function of how much ALC action is invoked. But I think any distortion 
> isn't helpful in this mode and creates a wide signal that isn't 
> appreciated by other users.
>
> This is a pretty good presentation on PSK and tuning a rig (Worth looking 
> at) http://kk7uq.com/html/download/IMD%20Presentation.pdf . I think you 
> will always find that papers on this mode recommend low, or if possible, 
> NO ALC action.
> 73. Merle - W0EWM
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