"Owen Duffy" wrote in message
...
"Jimmie D" wrote in
:


"Owen Duffy" wrote in message
...
K7ITM wrote in news:1186788470.852002.260460
@b79g2000hse.googlegroups.com:

On Aug 10, 2:28 pm, Owen Duffy wrote:
...
I don't think you can compensate for lack of f/b ratio in the
coupler, for example because the coupled lines are too long.
...
I'm curious what you mean by that, Owen...

Tom, I was thinking of several instruments, all of the coupled lines
type of construction, that on a s/c and o/c failed to indicate rho=1,
and showed
similar readings when physically reversed, suggesting it was not just
a fwd
/ rev matching issue, there was something about the coupler that was
too dependent on the location of the SWR pattern relative to the
coupler. Since
they worked better at lower frequencies, the length of the coupler
was likely to be a contribution.

Owen


Would this be a problem for a directional coupler designed for a
specific frequecy?


Jimmie

Jimmie, I am talking about the el-cheap inline SWR / Power Meter that is
often sold to hams with unrealistic specs.

You can / should always test the performance of the kit you are using to
determine if you should have confidence in it.

There are a bund of notes on testing a directional wattmeter in the
article at http://www.vk1od.net/VSWR/VSWRMeter.htm .

BTW, for your purposes, if you had a Bird 43 with an element that read
upscale on fwd power (250W element for your application), it is all you
should need to form a reasonable estimate of line loss and set the
transmitter to deliver 100W to the antenna. You might need a smaller slug
to make a measurement of RL on a s/c or o/c termination.

Owen

Well it a done deal,
Engineering support came out last night and ran the checks for us while Im
on vacation and recovering from minor surgery, Yaaay. They did it the normal
way and by measuring the return loss and they decided the "return loss
method" worked better. Not sure what better means at this point. accurate
enough and easier and faster would constitute better.


Jimmie