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Re: Old Micor Vhf PA ???

 

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Well,
great answers but i dont understand everything ,,i am not a tech as you guys!

If i understand ,on the Micor PA i could connect some wires (on the PA circuit) so at the ainstant 250 mw would be applied,detected? it would ,,,transmit ??

on my Master 2 PA that i add it was like that,if i applied 300mw it would amplified and bingo the repeater was On the air.


excuse me to be to ,,,simple in my explanation !

i may end by buying an rf amplier on Ebay? but they will never be as HD as the true repeater PA.

73/s and Best 2025 to all!

Gef
Ve2ckn



De : [email protected] <[email protected]> de la part de Kevin Custer <kuggie@...>
Envoyé : 5 janvier 2025 09:05
? : [email protected] <[email protected]>
Objet : Re: [repeater-builder] Old Micor Vhf PA ???
?
Karl,

The information you provided to Gervais is NOT correct.

On a MICOR VHF power amplifier - you have to switch the A- (A minus) during transmit.? This logic can be sourced from the PTT of the repeater controller.? In other words A- needs grounded during transmit.? A- is a connection on the side of the PA - and usually has a wire attached that plugs onto the station.? This can be easily accomplished using a relay or transistor sourced from the PTT logic.? Some repeater controllers can provide the logic directly as the current is not excessive.

----

The drive power level between a GE MASTR II VHF PA and a Motorola MICOR VHF PA is EXACTLY the same.?

GE Exciters put out 200mW and have nothing between the exciter and power amplifier.? Therefore the power amplifier has an input power level of 200mW.

Motorola MICOR VHF Exciters put out 400mW but an exciter band-pass filter that has 1.5 to 3dB insertion loss exists in between the exciter and PA.? As such - about 200mW is delivered from the BP filer to the input of the power amplifier.? Therefore, the Motorola MICOR VHF power amplifier is properly driven with a GE MASTR II exciter with nothing in between.

Kevin


On 1/5/2025 2:02 AM, Karl Shoemaker via groups.io wrote:

Gervais, ? The Motorola PA B- has to be switched in order for the amplifier to work (unless you modify it like I do). ?If you do have a "hot" PA be sure to protect it with an isolator and cavity if you are at a populated site.?
Also, RF power input standards are different between GE and Motorola; +23 and +26 dbm, respectively.? Best way to blow an amplifier is over driving it.
?
GE PA's can be repaired if you can find the parts and properly troubleshoot it. The hardest part to find may be the power control module. It's either blue or black on the outside with many pins.
So, isolate if it's a (power) transistor(s) or an IC-control problem. Also, the braid or strap between the boards have a habit of opening up. That's near the filter board. ?
?
Heat is not so much the big issue here, it's the extreme hot and cold cycling that destroys semi-conductors and other components
-
Regards, Karl Shoemaker
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