[Elecraft] KXPA100 Mobile Operations -- Power Output

[Matt Zilmer]

I was seeing 12.2V with 60W out on 20m with KX3/KXPA, but this was
measured at the relay enclosure (near the KXPA), and it had another
10A or so as loads besides (2m rig at 75W).  Didn't measure the
current, but it was probably around 30A total.  This is with the
battery alone.

I also saw full output (100W) with the KXPA and KX3 alone, with no
engine running.  Voltage at the relay was 12.3-12.4V.

With the engine running, no problem.

The DVM has never been calibrated, that I know of.  If it has, it's
been > 10 years.  It might read low or high.

I'm probably going to run a second Optima 55AH battery with its own
branch charging circuit, just for the KX3 and KXPA100.  This is a
future project, not something I have the time or money for now.

I'm using 8 AWG, and this is also what Moto used for Micors, Syntors,
etc., if 100W class transceivers.  I used to run a 100W UHF Syntor,
but gave it up to get some trunk space back.

73,
matt W6NIA



On Mon, 13 Jan 2014 12:17:49 -0900, you wrote:

>I need to correct some of my last statements on this topic (thanks to 
>Dave AB9CA/4 for pointing them out).
>
>I apparently was thinking of other battery chemistry than lead-acid 
>batteries.  A check with wikipedia reveals that full charge voltage, 
>open-ckt, is 2.1v per cell (12.6v for auto battery).  Fully 
>discharged open-ckt voltage per cell is 1.95v (11.7v) and 1.75v 
>(10.5v) when loaded.
>
>Matt was seeing full RF output with 12.2v at the amp.
>
>But that was with his engine running (alternator charging) which 
>ought to deliver higher voltage to the amp (if cable losses are low - 
>something like 0.5v drop if wiring is 8-awg).  Alternators run at 
>14.2v in full charging.  They have a voltage regulator that drops 
>this when battery reaches full charge (not sure what voltage that is 
>but seems I've seen >13v).
>
>I do not recall what gauge of dc wire was run to the 100w Motorola 
>VHF trunk-mount radios we used to install for police and fire, but 
>they held power pretty well with engine off (with fresh battery 
>charge).  I am thinking the wires were 12ga awg and 17-foot long 
>before cutting to length in each install.
>
>The rest of my suggestions for testing and connections are still good.
>
>73, Ed - KL7UW
>http://www.kl7uw.com
>     "Kits made by KL7UW"
>Dubus Mag business:
>     dubususa at gmail.com
>
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