Further down in the same online spec page it states "Compact unit ideal
for both desktop and mobile use". Note *mobile* use where the electrical
system supplies more than 13.8V with the engine running.
I find no mention of the KXPA100 being developed as a "portable" amp. I
have done searches of all Elecraft docs concerning the KXPA100 and find
NO mention of the word *portable* anywhere. Nor do I find any mention of
some nefarious board swap early in the products life.
Maybe the OP assumed because it has a carry strap that it is a portable
amp. Well...My TS520 has a carry strap and a DC-DC converter. No way
that can be classified as portable, it weighs 37lbs.
To be fair I have run it at field day but we had a 10KW diesel powered
generator on a trailer. Power was NOT and issue.
On 5/22/2016 4:46 PM, Jim Brown wrote:
Michael,
A careful reading of the online data sheet for the KXPA100 is
instructive here.
http://www.elecraft.com/KXPA100/kxpa100.htm
The first line says "100 watts at 13.8 V, 1.8 to 29.7 MHz and 80 watts
50-54 MHz PEP CW/SSB/DATA; ± 1 dB"
Two points: First, the amplifier is rated for 13.8V, NOT 12V. Second,
the rating is +/1 dB, which is +/- 20% power. Thus, 80W on the HF
bands is within spec for 13.8V at the amplifier terminals.
The second line says "13.8 VDC powered; 20 A typical current drain (11
V with lower output. 15 V max)"
This clearly means that the unit is designed and rated for 13.8VDC,
can be operated from 11V to 15VDC, and will have reduced output at
lower supply voltages.
Obviously, Ohm's Law dictates that resistance of the DC supply
conductors will reduce power supply voltage at the amplifier
terminals, so while we may have 12V or 13.8V at our battery terminals,
the voltage at the end of 6-12 ft of cable will be a bit lower with a
20A load. For example, the drop in 6 ft of #10 is 0.24v; for #12, it's
0.38V, and for #14, it's 0.6V.
As others have noted, the operating voltage in so-called 12V DC power
systems using lead-acid batteries is not 12V, but rather 13.8V. If you
buy an AC power supply for ham gear, it will likely leave the factory
with its voltage regulator set for 13.8V. Open the manual or the spec
sheet for nearly all ham gear and you will find the supply voltage
specified as 13.8VDC.
73, Jim K9YC
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