Kevin Custer wrote: > Eric Lemmon wrote: >> I was surprised to notice that, while the >> RF output power settings were almost exactly on the money at 5, 12, 25, and >> 50 watts into a dummy load, the DC input power to the radio did not track >> the output power- not even close! In fact, the DC input power at 5 watts >> output was about 85% of the DC input power at 50 watts output. And that is >> what toasted the PA module- the DC input power that was not converted into >> RF output power was, instead, heating the driver and the PA stages to >> destruction. > > Something is definitely wrong. I have messed with a lot of power > modules and radios and have never seen this type of action without > something being spurious. Efficiency of these modules do change with > applied drive, and differing control voltages, but not that much. You > didn't state exactly what the current draw was at the different levels, > so I cannot extrapolate the difference in efficiency of the module at > the different power output levels. In your case, however, were not > talking about a few percent, like we should be. > > I'd guess the module was spurious at the lower power levels. > > Kevin Custer
Or they're not really reducing drive at low power levels, but something else. I could see a cheap company actually just putting a resistor (or some other component) in series with the RF output, causing a mismatch. Incredible I know, but not outside the realm of possibility. -- Jim Barbour WD8CHL
