On Sat, 2006-09-23 at 13:10 -0500, Bill NY9H wrote:
> >
> >I have a Ten-Tec 9420 to power my Hercules II. It is essentially four 20
> >amp (or so) regulated 12 VDC power supplies. And it is interesting to
>
> I just went into the garage, ( my 9420 is mounted in a old kitchen
> cabinet on the garage wall , on the wall opposite my station setup).
>
> IT says 14 VDC... I knew it was not 12vdc,,, and I have no clue what
> the difference of 12 to 14 VDC will have on output , but the Herc is
> designed for 14.
>
> So when figuring batteries and chargers it might be wise to ask some
> of you guys with battery setups , what if any difference is noted
> with a regulated 12 vdc system.
>
> just a thought
>
> bill....
>
> and in response to any earlier inquiry: the value of a HERC II ...
> "PRICELESS"
I don't know for sure about Tentec designs, some exciters seem to be
more tolerant of varying loads than other brands, but in the optimally
designed PA, the load impedance to the transistor is picked so that with
14 volts, the peak negative swing gets down to about 2 volts giving a
peak to peak swing of 24 volts, or 8.6 volts RMS. For a 100 watt load
that means a load R of 0.734 ohms. With a 12 volt supply that swing is
reduced 2 volts (limited by the saturation voltage of the active
device), so the peak swing is 10 volts, peak to peak is 20 volts, RMS is
7.1 volts. 7.1 volts to 0.734 ohms gives 69.5 watts, a loss of 1.6 dB.
Which is too small to detect at the other end of an radio propagated
path, unless the signal was just at the noise threshold of
detectability, then a change of 1.6 dB may mean a S/N change of 3 or 4
dB.
--
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer
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