Thanks Eric and Brian for the info. I've been able to run it for 10 yrs @110
watts on 145.270 without any problems in an air conditioned environment. But
I'm moving it to a remote location without a/c. I guess I will leave it as
is, as I need the power as much as I can get. No duplexer on this machine.
Wide area crossband 8 rx site system.
Thanks again guys, Bruce KD4BOH.
----- Original Message -----
From: "Eric Lemmon" <[EMAIL PROTECTED]>
To: <Repeater-Builder@yahoogroups.com>
Sent: Tuesday, May 10, 2005 8:26 PM
Subject: Re: [Repeater-Builder] Micor mobile transmitter
> Bruce,
>
> Although you can disconnect half of the four final transistors and change
> the matching components appropriately to have a 50 watt PA, it's better to
> simply exchange the 100W amplifier board for a lower power board. I'm
> guessing that you could probably find someone to swap boards with, maybe
> even make a few bucks in the deal..
>
> It is not a good idea to reduce either the drive level or the PA supply
> voltage to achieve a lower power output, because the PA can become
> unstable. A solid-state PA is normally designed to present a stable
> source impedance which, in basic terms, is directly proportional to supply
> voltage and inversely proportional to PA current. Reducing the drive
> level will reduce PA current, thus raising the apparent PA source
> impedance and causing a mismatch with the load impedance- usually the
> reactive input impedance of a duplexer. This is not good, and is an
> invitation to instability. Reducing the supply voltage has the opposite
> effect on the apparent PA source impedance.
>
> If you have the requisite test equipment and time, you may be able to
> adjust both the drive level and the PA supply voltage to achieve stability
> at a lower power output level. This is a lot of work, and may be much
> more work than simply replacing the PA board.
>
> 73, Eric Lemmon WB6FLY
>
> brucenanney wrote:
>
>> What is the best way to reduce power on a 100 watt micor mobile for
>> repeater use? I have reduced the voltage in to 12.8 volts and have
>> developed a cooling system on the P.A. deck that has constant air flow
>> over the circuit board as well as the the heatsink.
>> Thanks, Bruce KD4BOH.
>>
>>
>> Yahoo! Groups Links
>>
>>
>>
>>
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>
> Yahoo! Groups Links
>
>
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>
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>
>
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