Odd power problem?

[Web Williams]

Just finished the conversion of my K2 to a K2/100. On SSB, power
seems quite robust, with my wattmeter showing 70~80 watts on voice
peaks (I would have expected about 40~50). On CW, I'm only getting
about 40~50 watts dead key (I would have expected 100). It seems
like this is backwards from every radio I've ever owned, and I can most
certainly live with this. I got every upgrade available (resistors,
caps, etc.)
before starting the build so all parts/firmware are current as of July
2005.
I really don't want to go back inside since everything else is performing
quite flawlessly. But in the event I ever have to go back inside in the
future for another reason, what should I look at as the culprit?

Thanks, -KR4WM

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[Dan Barker]

My first suspicion would be the test setup. How are you measuring power?
What supply voltage? What's it drop to on Key down or Voice Peaks? What's
the current Tx? What's the load?

Dan / WG4S / K2 #2456

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]]On Behalf Of Web Williams
Sent: Sunday, August 14, 2005 9:19 AM
To: Elecraft List
Subject: [Elecraft] Odd power problem?


Just finished the conversion of my K2 to a K2/100. On SSB, power
seems quite robust, with my wattmeter showing 70~80 watts on voice
peaks (I would have expected about 40~50). On CW, I'm only getting
about 40~50 watts dead key (I would have expected 100). It seems
like this is backwards from every radio I've ever owned, and I can most
certainly live with this. I got every upgrade available (resistors,
caps, etc.)
before starting the build so all parts/firmware are current as of July
2005.
I really don't want to go back inside since everything else is performing
quite flawlessly. But in the event I ever have to go back inside in the
future for another reason, what should I look at as the culprit?

Thanks, -KR4WM

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[Don Wilhelm-3]

Web,

Are you referring to the KPA100 internal wattmeter readings or some external
wattmeter?  If it is an external wattmeter, do you know its accuracy?  Have
you calibrated it?

Several possibilities occur to me - 1) You are driving an antenna with high
SWR and the KPA100 is reducing power because of the SWR; - 2) The internal
wattmeter in the KPA100 is not properly calibrated and is detecting that the
KPA100 output is at your requested poswer setting when the actual power is
considerably less; - 3) The internal wattmeter pot in the KPA100 is not set
correctly and is incorrectly reporting a high SWR condition.

I suggest calibrating both your external wattmeter and the KPA100 internal
wattmeter with a known good 50 ohm non-reactive dummy load (check it with an
antenna analyzer) and an RF Probe measuring the RF Voltage across the dummy
load.  Use the 40 or 80 meter band so the added capacitance of the RF Probe
does not have a significant effect and calculate the actual power output as
V*V/R where R is the resistance of the dummy load.  Note that your dummy
load MUST be resistive only - no inductive or capacitive component if good
accuracy is to be achieved.  A power level somewhere between 20 and 50 watts
can be used for the calibration.

73,
Don W3FPR

> -----Original Message-----
>
> Just finished the conversion of my K2 to a K2/100. On SSB, power
> seems quite robust, with my wattmeter showing 70~80 watts on voice
> peaks (I would have expected about 40~50). On CW, I'm only getting
> about 40~50 watts dead key (I would have expected 100). It seems
> like this is backwards from every radio I've ever owned, and I can most
> certainly live with this. I got every upgrade available (resistors,
> caps, etc.)
> before starting the build so all parts/firmware are current as of July
> 2005.
> I really don't want to go back inside since everything else is performing
> quite flawlessly. But in the event I ever have to go back inside in the
> future for another reason, what should I look at as the culprit?
>
> Thanks, -KR4WM
>
>

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