[TenTec] Digital (PSK31) Communications

[Bob McGraw - K4TAX]

A comment to the point of setting vs. controlling the power on the Jupiter.

For modes like PSK-31 the Jupiter should be configured to operate at its 
rated output power or 100 watts.  Then the actual power output should be 
controlled by the PSK-31 software or the sound card output level or 
interface output level to the Jupiter so as to cause the Jupiter to produce 
some 25 to 35 watts of power.  This will prevent the ALC activation and 
subsequent distortion from being generated and transmitted.  Also, any SP or 
speech processing should be OFF.

It should be noted that the PSK-31 signal will cause the power output to 
vary slightly depending on if idle or data is being transmitted.  This is 
normal and the amount of variation depends on several factors, such as tone 
frequency, power meter response and dampening and etc.

Here is the basic NO NO.  Reduction of the Jupiter power to 25 to 35 watts 
and then have the sound card audio drive the Jupiter to 25 to 35 watts will 
activate the ALC and subsequent distortion of the transmitted signal will 
likely result.  This produces a transmitted signal that is several hundred 
Hz wide and thus an annoyance or interference to others on the band.

In general it is frowned upon to run "high power" on PSK-31.  The issue with 
this lies in the fact that an exceptionally strong signal adjacent to a weak 
signal, both within the IF passband,  will cause the strong signal to 
capture the AGC and thus further suppress the weaker signal.  As a general 
"rule of thumb" one should always operate with actual PSK-31 power output 
being no more than 25% to 35% of the rated transmitter power.

73
Bob, K4TAX




----- Original Message ----- 
From: "ron" <roncasa at verizon.net>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Saturday, February 02, 2008 9:42 AM
Subject: Re: [TenTec] Digital (PSK31) Communications


> Henry Mackey wrote:
>>
>>   The power setting on the Jupiter was at 100%. However, I would reduce 
>> the power according to the rigs meter to 20-25 watts and avoid any ALC.
>>
>>
>
>
> 25 watts??
>
> For a mode that only needs minimal wattage??
> Try less and be amazed. (the spectrum would also be cleaner if we all did)
> (smile)
>
> Ron
> "the 516 is a keeper"
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