Batboard

Hi all, Does anyone know how I can drop the output power down to about 10 watts without useing an attenuator externally?. The power control will only let me drop it to about 20 watts and would like to use an amp on 6 meters with a 10 watt input. any help appreciated. thank you. Davie n 3 c h u at atlanticbb.net dot net

Most of those PA's really get ineffecient when you turn the power below about half the design power.
So, if that is a 110 watt, you really don't want to go below about 60.
If it is one of the other power ranges, same thing applies.
You might be able to physically bypass a stage in the amp.
I can't recall what the driver portion is, but it might be in that range.

The lowband has a reputation for going spurious on low power Tx. There was a 60 watt lowband Syntor X version if you can find one. Run these at rated power or check each Tx frequency with a spectrum analyzer. The VHF and UHF are designed go do down to half their rated power. Another difference between the lowband and VHF, UHF or 800 is the lowband is the only Syntor X / X 9000 to use PIN diode Rx/Tx switching. All the others use relay Rx/Tx switching.

How about changing the bias resistance on the PA? Davie

These PA's run class C so there is no bias. Your best bet is to see if you can run just the driver stage. The interstage coupling is 50 ohms so you can break it and solder in a piece of coax. I really dont know the low band PA to tell you for sure. Take a look at it.

Chris

I was wondering why anyone would want to drive an amplifier with a low band Syntor X drawer. It puts out over 100W in its natural form, which I would think would be more than enough power for most any use, but maybe I am missing something...

Well I'm using a "0" gain antenna, PD128 at 30 ft in the middle of nowhere as far as 6 meter activity is conserned and sometimes you need to reach out and touch someone.