Re: No power increase with higher voltage?
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If the idling current is set high it may be possible that the two RFC's in the
IRF510 stage are saturating, making them look more like wires than like
inductors.
_._
On Fri, Feb 9, 2018 at 4:50 PM, John Backo <jabac@...> wrote: Vic:
Is there any difference in the distance achieved with QSO's
using 12v. vs 24v? Or is there any difference in the reported
received S level when using 24v vs 12v?
There are several possible explanations.
1) There is oscillation at 24v and this is contributing to a false
sense of power output. It is most likely being removed by the LPF.
2) There is insufficient drive at 24v -- This is usually corrected by
increasing the mic gain. For a good solution, see K.P.S. Kang's
solution at .
3) The LPF or output? transformer is killing the signal. This is unlikely
since it works at 12v very well and no one has reported anything similar.
4) There is really no 24v on the drain of the IRf510. This is unlikely
since you are reporting a good voltage there. (Incidentally you mixed up
source and drain).
6) Your measuring equipment is not telling you the truth. Really, you need
an oscilloscope to measure the true RF output at each stage. A good RF
probe will do the same thing, however, and it is easy to homebrew.
Why are you using a DVM to measure RF?
Since you report good audio with QSO's, I suspect the last, though I would
not discount oscillation as the culprit. You need to know the RF level at each stage
through the PA system from drive to output at the antenna. It is also possible that
your antenna is not matched well enough. (That would mean mysterious increased
heating of the heat-sink at 24v; you probably should increase the size of the
heat-sink anyway if you are going to use 24v. Easy enough to do.) Measure the
SWR at 12v and 24v, BEFORE the antenna tuner (if it is used) and AT the antenna.
Really, I think you need to rethink your measuring equipment first.
john
AD5YE
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