Steve,
It is not likely that you will be able to achieve a 000 indication when
nulling the KAT2 - in fact I believe that fact is pointed out in the
manual. You should strive for the lowest reading possible, and if that
lowest reading is less than 010, all is likely OK. Do not simply stop
if you get a reading below 010, the proper point is the lowest reading
that you can obtain - use the null point and not any absolute value.
If your dummy load is not precisely 50 ohms resistive only at the
frequency of operation, the base K2 will give either a higher or lower
power indication. Since the KAT2 has a real wattmeter, it measures
power rather than only the RF voltage (the base K2 measures only RF
Voltage) - so with the KAT2, the dependency on having a precise 50 ohm
non-reactive dummy load is removed. Since I have not measured your
dummy load with an antenna analyzer at the operating frequency, I cannot
really answer your question directly, so I just give possible reasons
for the apparent discrepancy.
Any residual inductance in the tuner can have an effect on the full
power output available from the K2 - but that reduction should be less
than 1 watt if all is within the normal range.
73,
Don W3FPR
Steve Banks wrote:
Hello Everyone,
I just completed the KAT2 accessory for K2 S/N 5615 (my second K2), and I'm
wondering whether my KAT2 calibration results seem to agree with others'
experiences with this tuner.
Here's a digest of my experiences:
All KAT2 MENU FUNCTIONS operate exactly as specified in the Assembly
Instructions.
K2 SUPPLY VOLTAGE = 13.1 VDC (SLA Storage Battery used on my test/assembly
bench)
BRIDGE NULL (C55) result was 007. I was not able to achieve a CALn of 000
as the manual suggests, but 007 was stable and easily repeatable with C55.
Since C55's adjustment seemed a little twitchy at first, I
rewound/reinstalled T1 on the KAT2 Control Board and replaced the D1 and D2
1N5711 diodes on the bridge. Reinstalling these bridge components produced
identical results as the first time around. CALn still stays put at 007
with an occasional flicker to 006.
The rAnt menu function was turned OFF on all bands for all measurements.
All voltage measurements for CALp settings were done with my Tripplet Model
60-NA VOM and also with my RS DMM (a Fluke clone) using their regular test
leads. The RS meter was likely more accurate, but both were very close to
each other.
CALp (adjusting R1) was done at 7000KHz using a "requested power" (POWER
control) of 5.0 watts as instructed on p.17 of the KAT2 manual. In lieu of
a "known accurate wattmeter", which I don't have, I used both of my meters
to measure the DC voltage at TP1 of my Elecraft DL1 dummy load, using each
meter's regular test leads. Both meters were in close agreement as I
measured, and remeasured, all voltages. I used the suggested formula on the
Elecraft DL1 Instruction Sheet P(watts) = ((V (volts) x 1.414) + 0.15) ) ^2
/50 to compute the CALp power. I reset R1 accordingly as the instructions
direct. I repeated this process several times and was satisfied that all
seemed well. R2 was then reset to match the physical position of R1 as
instructed in the manual. (In case anyone wonders, neither meter seems to
like my DL1 RF probe. I haven't yet figured out why -- maybe an open diode
or a cold solder joint.)
After all the CALp, CALs and CALn adjustments were completed, I then reset
to the Pout menu function to measure the K2/KAT2's actual output power. At
the very bottom edge of ALL EIGHT BANDS, Pout was within a few tenths of a
watt of the requested 5.0 watts.
I then decided to see what the Pout results would be at the same frequencies
but at a requested power of 10.0 watts. Again, all eight bands' results
were within 1 watt of 10.0, except for the lower edge of 10m, which reported
a Pout of 8.5 watts. This still seemed OK (10m Pout rolloff might be due to
the K2 FA transistors' limitations.) The other seven bands' results were
all within a few tenths of one watt of 10.0 watts.
Finally, I decided to measure Pout again still at the same frequencies, but
at a requested power of 15.0 watts. The results on 80m, 40m, 30m, 20m and
17m results ranged between 13.3 and 14.5 watts. On 15m Pout was 12.9 watts;
on 12m it was 10.3 watts; and on 10m it was 8.6 watts.
Having reported all this, my question is simple: Do these KAT2 calibration
and power output results look reasonable to you? I've noticed that WITHOUT
the KAT2 tuner attached to the K2, the reported Pout is somewhat higher; 15
watts is easily achieved on most bands except for 12m and 10m. I suspect
that the KAT2's results are more accurate than the basic K2's without the
tuner, but I'd be interested in your comments.
Thanks for the bandwidth and your wisdom. Assuming all seems well to you,
I'll button up the KAT2 and KIO2 port in the top cover and move onto the
KPA100 assembly.
73,
K0PQ
Steve Banks
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