Power fold back - SWR

486dx4 · Post by **486dx4** » Tue Jun 20, 2006 3:48 am

Does anyone know if any or none (or some) of the motorola mobile/portable radios have an SWR power "fold back" circuit that cuts the output power on the radio if the SWR (reflected power) gets too high? they usually cut power back at 2:1 or higher ratios. You see this feature in Ham gear often. I would guess that since this is commerical gear these mobiles would be able to deal with things like this in some manner. Or, maybe this is not necessary since you perhaps are not hombrewing with antennas too often with the commercial stuff. No blown PA's/Finals yet but I'm curious.

Thanks...

Will · Post by **Will** » Tue Jun 20, 2006 2:27 pm

This depends on the radio model. Most M mobiles have a power foldback circuit.

Maxtrac/Radius/Mitrek have current sensing for power control.

GM ect have the current sensing and tempature sensing.

Spectra, Syntor, SyntorX9 have current limmiting, forward/refelected sensing and tempature sensing to control TX power.

High powered Spectra, Maratrac, and Mitrek also have overdrive control.

Just an overview, did you have a specific model in mind?

486dx4 · Post by **486dx4** » Tue Jun 20, 2006 4:47 pm

Very good overview... thanks for the info. I use the CDM / Waris mobiles (750 and 1550). Its interesting that temp sensing is involved with some models.

Thanks again...