[Yaesu] FT-ONE - low output.

[Dr. Gerald N. Johnson]

When a rig protects on reflected power, it won't let there be enough 
drive to get much forward power. If a rig is properly protected it won't 
be damaged by a high SWR load like an open on the coax connector.

First check be sure the coax from the rig to the dummy load is good, 
then that the dummy load is good. Check with an external wattmeter or 
SWR bridge.

Generally the SWR metering is after the low pass filter that is often a 
separate module from the PA because SWR metering with the strong 
harmonics from the unfiltered PA would be relatively useless.

Tentecs are known to mess up transmitting because of diodes in the SWR 
bridge having gone bad. So that's a place to check. A diode not 
rectifying forward power any more puts the ratio of forward to reverse 
very high lots of reverse, no forward and puts the rig into shut down. 
Seems like the Tentec diodes go during thunderstorms.

73, Jerry, K0CQ

On 5/27/2011 5:08 PM, Dr. David Kirkby wrote:
> I think I've managed to screw up my FT-ONE by transmitting into a bad load. The
> collector current is not going above about 1 A. If I used set the meter to FSD
> in the forward position, switching to the reflected actually shows beyond full
> scale! This is with a 50 Ohm load.
>
> I'm not sure if the sensing of the RF has gone wrong, so the PA is shutting down
> as the reflected power is apparently so high.
>
> I've not poured over the service manual yet, but does anyone know if the sensing
> for forward and reflected power occurs in the PA unit?
>
> Any ideas?