Can you give us a magnitude, for example for a g5rv on 3.8 MHz fed with 50
feet of 50 ohm coax. Is it .5 or 5 dB?

Or we can be more specific and say we want to match
a 50 Ohm source to R 5000 -J720 using an MFJ989C. What loss is to be
expected?

Granted there are cases of attempting to load a short (with respect to
frequency) antenna that has extremely low values of R can cause large
losses. I would think that a general statement could be made about antennas
that are 1/2 wavelength or longer at the operating frequency and the
magnitude of losses one could expect from the typical tuner.

Is there no way to quantify the losses, no rule of thumb, should we all
throw our tuners away because they may have unpredictable horrendous losses?
What steps should be taken by the average amateur to obviate these losses.

I am at a loss to understand how bad the losses are that you and Cecil refer
to. Can you lead me from the darkness Sir!.


"Roy Lewallen" wrote in message
...
Fred W4JLE wrote:
Can you give us a typical loss for a tuner matching a G5RV?

No, sorry, I can't, and I don't believe there is such a thing. It's
possible of course to find the input impedance of any wire antenna like
the G5RV at each of the frequencies of interest. But transmission line
lengths and impedances vary, which transforms the impedance seen by the
tuner. Those impedance changes can be dramatic, and can result in widely
varying tuner efficiency. On top of that, you have the variations in
tuner topology and construction which makes a "typical" tuner also an
elusive beast. I'd be very suspicious of any "typical" tuner loss
figure, and wouldn't expect to see it in practice unless the conditions
are spelled out really well and my setup was very similar.

You see, I'm not a true Guru. A real one wouldn't waffle like this, but
would give you a positive answer, and you'd very probably never have
reason to doubt it.

Roy Lewallen, W7EL