RadioBanter - View Single Post - Length of Coax Affecting Incident Power to Meter?

August 11th 03, 10:31 PM

(Tom Bruhns) wrote in message om...

:-) The meter-needle zero generally not a very big part of the
problem! Yes, it's the coupler (bridge) inside that you want to make
sure is calibrated for your reference impedance. If it's not
adjustable, at least learn what it is calibrated to, or how good it is
for your reference impedance.

It's all supposted to be for 50 Ohms, or course. And that is the
only adjustment on the meter.

The easy way to insure proper operation is to present the
transmitter/amplifier with the right load. A properly calibrated SWR
meter (or as Reg would have it, a "transmitter loading indicator")
will tell you when you have such a load. Yours is telling you that
you do not. In such a case, I'd work on a match to the antenna (or
the Cantenna or whatever) first--well, right after making sure the
meter was telling me the truth or something close to it. When you get
that correct load, then the length of coax won't matter noticably,
assuming the SWR meter is calibrated to the line impedance.

I've never seen an SWR meter that wasn't designed for 50 Ohms...
:/

If you mean adjusting the meter so that the forward power is full
scale deflection, well, that's not needed for a cross-needle SWR
meter.

I'm gonna try the long RG-58 trick...

Slick