[Elecraft] Experience with KXPA100

[Igor Sokolov]

Hans,
I did the same tests and indeed the lowest efficiency is on 10v and 160m 
bands  with output power of 94 W and dissipated power of 135 W. I did not 
measure 6m. But compromise like that might have been expected in the unit 
covering such a great span of frequencies.
Regarding the low output power, it much depends on the voltage of the power 
supply and voltage drop on the feeding wires. With factory supplied feeding 
wires and voltage of 14.8 V set on the power supply I can get  between 94 
and 110 W out on all the bands. The voltage drop at this power is about 1.2 
V according to KX3 meter. Therefore at 13.6 V by the meter KXPA100 indeed 
delivers close to 100 W. I get only around 84 W on 10m band when the amp is 
fed from 13.2V LiFePO4 battery. The voltage meter of KX3 shows then 11.1 V 
at that power.
IMHO KXPA100 is pretty sensitive to voltage of the power supply.

73, Igor UA9CDC
----- Original Message ----- 
From: "Hans J Rasmusen OZ7BQ" <oz7bq at yahoo.dk>
To: <elecraft at mailman.qth.net>
Sent: Wednesday, June 25, 2014 1:11 AM
Subject: [Elecraft] Experience with KXPA100


Hello,

My KXPA100 ser.nr. 00822 has now been on the air for several months and 
produced several hundred QSO's. The performance however, is mixed.
The output power varies from one band to another with the output set on the 
KX3 to 110 Watts and using the KXPA100 utility for meetering and a dummy 
load. The antenna tuner is in manual and SWR indicated to be between 1:1 and 
1:1.1 from 160 M to 10 M.

The best band is 20 M, where the KXPA100 will produce 112 Watts out with 5.5 
Watts driving power and an indicated power dissipation of 62 Watts.
The worst band is 40 M where the KXPA 100 only will produce 83 watts out 
with 2.8 Watts drive and an indicated power dissipation of 92 Watts.
On 80 M the KXPA100 utility shows a power dissipation of 118 Watts and an 
output power of 89 Watts.
Except on 20 M no band produce more than 90 to 95 Watts output.


I am surprised by the big variation in efficiency. Almost twice the loss on 
80 M compared to 20 M. Besides there seems to be plenty of drive power, so 
why less than full power on most bands?

Has anyone else observed similar variations?

73 OZ7BQ, Hans Jørgen (Joe)
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