I read his article. He uses an RF filter. I might try that.
My meter is a "good" one, a Fluke. But of course I've never sent it out
for calibration.
73,
Victor, 4X6GP
Rehovot, Israel
CWops #5
Formerly K2VCO
https://www.qsl.net/k2vco/
On 05/06/2022 16:12, Jim W7RY wrote:
One also needs to make sure they are measuring the filament voltage with
a true RMS voltmeter.
Most cheap meters wont do that.
Did you take a look at W8JI's site for measuring filament voltage. He
does is successfully with drive power.
73, Jim W7RY
On 6/5/2022 6:04 AM, Victor Rosenthal 4X6GP wrote:
I did measure the voltage at the tube pins. I haven't measured it
while transmitting, because the RF drives my meter crazy. I assume the
voltage drops a bit. Unfortunately I no longer have my trusty analog
voltmeter. I wish I did.
I'll measure the line voltage. But the only thing I can think of that
would cause that to increase after long transmissions would be if the
breaker on the line heated up and lost resistance. I have never heard
of that!
73,
Victor, 4X6GP
Rehovot, Israel
CWops #5
Formerly K2VCO
https://www.qsl.net/k2vco/
On 05/06/2022 6:19, Jim W7RY wrote:
*I'm curious Vic...*
*See below"*
On 6/4/2022 4:35 AM, Victor Rosenthal 4X6GP wrote:
This isn't a problem, just a phenomenon that I would like to
understand.
I have a TL922. Mods include directly grounded grids. I also
measured the filament voltage with my Fluke true RMS meter and put a
small resistor in the primary of the filament transformer to provide
exactly 5.0v in standby.
*Where did you measure this voltage. Best is to wrap a small wire
around the tube pins, (all 3 of them) and measure the voltage at each
tube.*
It has been running with the same genuine Eimac 3-500Zs in it for
about 6 years.
So here is what happens: after a longish CW transmission, the power
output INCREASES. On 20m, for example, it may go from 1200 to 1400
watts. When it cools, the power drops back.
I've noticed this with several wattmeters. I have observed no change
in SWR when this happens (it's 1:1 thanks to a Johnson KW Matchbox).
It happens when the amp is driven with an Elecraft K3 and also a
TS890s.
I'm interested in hearing theories about why this might occur.
*I cant add anything about what your seeing... Other than is the line
voltage changing?
*
*73, Jim W7RY*
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