Posted by
Mike WA8BXN on
Mar 09, 2012; 11:03pm
URL: http://elecraft.85.s1.nabble.com/high-power-tuner-tp7314904p7359876.html
I can think of a few ways to investigate a tuner's efficiency. Google
searching can probably give more.
You can read the inductor and capacitor values selected by the 998 and then
do a circuit simulation of the L network and determine current through the
inductors to find their ohmic losses.
Second, you can connect known non-inductive resistors (of different values,
throw in some inductance or capacitance too) as the output load and then
with an RF voltmeter determine the voltage across the load and then
calculate the power out. You will have to calculate the phase angle of your
load as well if its not purely resistive. This method could be done using
low power so its easier to build the output loads.
You could probably also measure the temperature rise of the tuner in
operation (put it in an insulated box).
Granted, there may not be a simple off the self instrument to do it, but it
can be done!
73 - Mike WA8BXN
-------Original Message-------
From: WILLIS COOKE
Date: 3/9/2012 5:31:30 PM
To: W5RDW;
[hidden email]
Subject: Re: [Elecraft] high-power tuner
I wonder how those that claim a certain efficiency for a MFJ-998 or any
other antenna matching device are measuring the output power. No watt meter
that I know including the famous and antique Bird can measure power with any
degree of accuracy unless the load is very near the nominal value (usually
50 ohms). If you need a tuner, your antenna does not meet this criteria so,
what are you using to form your opinion? I suppose that you could compare
two tuners for a relative efficiency by using the same transmitter and
antenna and a field strength meter. Of course, if you are running near the
rated power, you can watch for smoke and get a one time opinion that the
device was not efficient enough to survive.
Willis 'Cookie' Cooke
K5EWJ & Trustee N5BPS, USS Cavalla, USS Stewart
______________________________________________________________
Elecraft mailing list
Home:
http://mailman.qth.net/mailman/listinfo/elecraftHelp:
http://mailman.qth.net/mmfaq.htmPost: mailto:
[hidden email]
This list hosted by:
http://www.qsl.netPlease help support this email list:
http://www.qsl.net/donate.html