skipp025 wrote: > The more famous surplus commercial radio 224 MHz conversions > replace the PA with a Hybrid RF Amplifier Module... wonder if > they also include SWR Protection?
"They" don't - at lease not all do, but in the case of the MICOR mobile - the power set functionality (power level setting, power leveling, and SWR protection) is retained. This is because the VHF directional coupler works very well at 220 MHz, and if done right, can still drive a power transistor; which then controls the hybrid module. Scott Zimmerman/Repeater Builder builds a nice PC interface board that allows all of this to happen easily: http://www.repeater-builder.com/products/ampbd.html The picture on the right (MICOR mobile installation) shows the TO-220 pass transistor and you can see the little purple lead from the power set board coming through the PA wall and connecting to the base of the pass transistor. Because, in a MICOR, the power set control is done with circuitry that is separate from power amplifier board - this protection is not difficult to maintain. The interface board allows easy installation of the hybrid and even incorporates the reverse polarity diode that gets removed when you discard the original MICOR VHF PA. In the case of the GE MASTR II, power control is done with a simple pot, and all SWR protection, leveling, etc. is bypassed/eliminated - at least with this interface board. Maybe someone has hacked the MASTR II PA to allow for the incorporation of its protection in a 220 conversion - but I have never saw it if it has been done. Kevin Custer
