Bret,
I am not certain what you mean by the phrase "the RF watt meter built
into the rig reads correct on 80 and 40, but does not reflect the lower
power output on the higher bands, its still pegged". What do you mean
by "pegged"?
Is the internal RF meter indicating a high RF voltage? If so, you
should believe that the RF voltage is really high and something is wrong
with your test setup. The detector used in the basic K2 is a simple
diode detector and does accurately reflect the RF voltage, and the
microprocessor calculates that value to watts with the assumption that
the load is 50 ohms resistive.
Is your load at the time of these measurements a good 50 ohm resistive
dummy load?
If you do have a good 50 ohm dummy load on the K2, then I would strongly
suggest that you check your connecting coax link before doing anything else.
What kind of power meter are you using? How has its accuracy been verified?
We need to know exactly what your setup is before we can provide
informed answers to your questions.
How are you measuring the current draw? Is this the indication on the
K2 or are you using some other measuring device?
All in all, what I can say at the moment is that the base K2 will
control its power output according to the RF voltage indicated at the
internal diode detector. That detector is not a wattmeter and needs a
good 50 ohm resistive load in order for the K2 to control the power output.
As far as adjusting C21 - adjust any of the bandpass filter elements at
a power of 2 watts or lower. Attempting to adjust them at higher power
levels can lead to incorrect alignment due to several other factors.
How are you determining that the harmonic content "goes way up"? That
is unusual and indicates that you have a problem with soldering or
incorrect components somewhere.
The usual cause of high current draw coupled with low power output is
the Low Pass Filters and/or the T4 circuitry. Do you have T4 properly
wound?
73,
Don W3FPR
Brett gazdzinski wrote:
After work today I got much closer with the vfo calibration,
and moved onto the TX alignment.
I hooked up the dummy load and the 0-20 watt meter.
3.5 MHz 12.5 watts out, 2.7 amps
7 MHz 14 watts out, 4.3 amps
10 MHz 10 watts out, 2.4 amps
14 MHz 8 watts out, 2.3 amps
18 MHz 9 watts out 1.8 amps
21 MHz 9 watts out, 1.8 amps
24 MHz 6 watts out, 1.5 amps
28 MHz 5 watts out, 1.8 amps
13.8 volts per my DMM.
When tuning C21 in the 30 meter bandpass, the output power
would take off and go to 20 watts till I turned the power down
then back up, then it acted normal.
In my kit, C22 was a 2.7pf, not the 3.3pf listed.
I assumed the 2.7 was what they could get instead of the 3.3.
Something is really wrong there, but the parts seem to be
the correct values, the toroids have the correct turns, etc.
I checked the voltage at the RF output detector and its ok.
I looked into all the trouble shooting steps in the manual,
made sure all the correct parts are in the correct places,
the toroids have the correct turns, etc.
Nothing gets hot, or even warm, despite the 5 minute key downs
at full power.
Looking at things on the spec an, after the power knob
is up past 1/2 to 3/4 the harmonics go way up, but I might
be picking signal up before the filters.
One other thing I noticed, the RF watt meter built into the rig
reads correct on 80 and 40, but does not reflect the lower power
output on the higher bands, its still pegged.
I looked at the signal on the spec an, probing the driver input and
output power levels, and I don't think the drive falls off,
I did not probe the output of the power amp as it would risk
the spec an (1 watt max input).
I don't need lots of power out, but dislike when something does
not work up to spec.
The receiver seems to work very well, although I have
not run the spectrogram on the filters yet.
Brett
N2DTS
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