>I'm also wondering if someone were to come out with an decent all
>band rig in kit form that ran up to 20 watts out, if anyone would
>buy it? Most likely it would have to sell for 500 bucks to be
>any good.
>Maybe one of the kit places will offer a 20W amp option for thier
>QRP rigs. In spite of the FCC regulations, if it's a class C amp,
>can't see how they would be too concerned. Not exactly suitable
>for CB rigs....as if it mattered anyway...
>de KD1JV Steve in NH
Actually, I noticed that the 38 Special is much like my homebrew 40m
Sierra like XCVR in that *everything* in the XCVR runs off of
regulated 8v except for the IRF510 final. I also used a IRF510 as the
final in my 40m rig.
Before I modified my output network to get more power, I was limited
to about 2w. This really hurt me in the early going of the 40m fox
hunt.
To increase my power, I would run my rig at 24v. Since power is
V*V/2R, doubling the voltage should have increased my power output by
a factor of 4, but I was able to get about 6 3/4 w.
The 100v rating of the IRF510 (or the 80v rating of the IRF511) gives
plenty of margin for this kind of operation.
The end result of all of this is that with proper heat sinking, it is
likely that a 38 special "as is" may be capable of putting out 15 to
20+ watts just by going to 24v.
In fact, at 35v (the limit of the 8v regulator), a 38 special could
perhaps put out 42 watts!!!! How many 40w QRO rigs do you know of for
$25!
However, more is not better! Remember that a 7808 regulator is good
for at most 35v input.
As long as designers keep to regulated voltages everywhere but at the
final, and as long as we keep with *****cheap***** (but rugged) MOSFET
finals, a QRP rig can be a QRO rig with the change of a power supply
(and a *much* bigger heatsink).
Just another idea for a *very* cheap QRO/QRP rig. Who needs another
amplifier?
- Dan Tayloe, N7VE (ex-KK7BD), Phoenix, Az QRPL # 696, Az ScQRPions
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