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[AMPS] 2 tone intermod test

To: <amps@contesting.com>
Subject: [AMPS] 2 tone intermod test
From: measures@vcnet.com (measures)
Date: Wed, 24 Nov 1999 01:35:11 -0700
>
>>>........ I guess I can run a
>>>test with voice but it just seems so subjective and would
>> be hard to show
>>>the results to anyone at the Icom factory in case I decide to send the
>>>exciter in for a tune up.
>>>
>>IMD products are pretty much fixed if the RF output unit has the
>>specified idling current.
>>>
>>cheers, Dave
>>
>>-  Rich..., 805.386.3734, www.vcnet.com/measures.
>
>
>I've come to the conclusion that ALC problems or poor design
>account for a lot of the speech related splatter that
>doesn't show up with 2 tone tests. 

often true

>The TS830 seems good
>(until the driver fades) while my FT990 is horrible. As soon
>as the ALC comes into play, there is a leading edge spike of
>typically double the set power for a few ms before the level
>settles to nominal. 

- which indicates that the mic. gain is set too high.  On a solid state 
radio, ALC indicates that overshoot is taking place.  Less ALC is better 
than more ALC.  I run my ts440 where the ALC barely flickers.  I know 
that a midrange ALC indication means more feculence.  If folks monitored 
peak RF output voltage with an oscilloscope they would be better off.  
When using an amplifier that does not use a regulated anode supply, more 
mic. gain always means less PEP.  

>You certainly know all about it for +/-
>20kHz when listening on a monitor rx while talking. 

The only thing that matters is:  how far down is the splatter?. 

cheers, Steve

-  Rich..., 805.386.3734, www.vcnet.com/measures.  


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