Kevin;
I would watch the voltage feed to the PA as just as important as
the specific power level.. The GE power Supply idles high ~15v but drops
into the lower 12.x volts under full load, you can watch it load down as
you increase power.
An Astron RS50 for instance may be set for 13.8v and at full power
the station could make as much power as 150 watts. In this case backing
down ( via only the power control) to 50 would potentially put the amp in
an unstable region and make it potentially spurious... setting for 70-80
watts on 12.5 volts should yield a good combination...
The main thing I am pointing out, which did not pup up in prior
discussion of Astron vs GE supply is Astrons in general are higher voltage
to start, at rated power draw, and the foldback design of the GE supply
reduces itself based on load. GE supplies become self limiting in the power
dept. A higher input voltage requires a lower power control setting to
achieve only rated power, which in general means a lower ( read more flaky,
as well as more difficult to hold stable) region of the pot, which
restricts gain of earlier amplifier stages of the amp, but not later high
current ones.. This is the scenario that makes for spurious output...
Older 70's series PA's suffered from this and consequently most
suggested power reduced settings spec'ed for MII at that time only called
for max power de-rate of about 50% at 12.5-12.8 delivered to the PA...First
generation VHF 110w amps were notorious for this when run at 13.8v, and low
power settings.
Running the PA on the lower end of 12v ( which is better/easier
for battery backup purposes anyhow) seems to be a best plan to start with,
and then a slightly reduced power setting should stay in the upper half of
the power control pot settings... yielding 70-80 watts and stable....
Just my 2 cents....
Doug
KB8GVQ
At 11:07 AM 12/22/2004, you wrote:
>Thanks much Doug. I figured as much. I think running the PA at half
>power should be safe then.
>
>Kevin
>K2KMB
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/Repeater-Builder/
<*> To unsubscribe from this group, send an email to:
[EMAIL PROTECTED]
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
