Most, if not all, batteries will be dropping below 12vdc before much use.
While I have never tried to use my Scout (dunno if its early or later run)
for very long on only a battery I do plan to use my 526, 6n2, rig QRP
portable some and this whole thread is interesting to me. What it appears
is that to use probably all solid state rigs away from our AC mains is
going to require a bit more thought (and weight!) The DC-DC inverter could
be a good solution and one that could be designed to provide stable DC to
the rig. Yes, there is going to be some loss through the device but I
haven't found a free lunch anywhere else yet either. As an alternate, a 7
cell battery comes to mind. It would have an initial voltage of 15.4
(2.2*7) but would rapidly drop to 14.7 or less and could drop to ~1.7vpc
before hitting the 12vdc output "malfunction" point. Hopefully enough of us
are true hams and could build our own charger for the 7 cell battery.
As an aside, I like to do VHF/UHF contesting which usually involves taking
all our beloved gear to the top of some mountain for a weekend of field day
type operations. VHFers are seldom known for trying to run QRP and the
League doesn't even bother with a category for multi-op QRP VHF. I have
usually done the 6m station and have had problems with generator sag when
the Kw hits the RG-389 feed line I use. This even occurred with >6Kw
generators feeding the power. This last September I tried another approach
by feeding the amp with a 1.4KVA UPS. This worked splendid except the UPS
didn't like the trashy power from the generators! The final solution was to
run the UPS from a Honda 1Kw 'inverter' generator. Yes, the generator
couldn't keep up with the amp but the UPS could and just used the battery
during the surge and politely went back to the clean power from the Honda
after transmit and, of course, charged the battery back up a bit. For those
of you that haven't seen the 'inverter' Honda, its an EU1000i (there is now
a 2kw version). This is a Kw you can easily carry in one hand, stand next
to and talk normal and it is VERY fuel efficient. Yes, it does cost more
per watt but you will fall in lust when you use it.
de KD4GT
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