On Tue, 19 Dec 2006 15:04:58 -0500, Fred McKenzie wrote in :
In article ,
"Mike Andrews" wrote:

Some friends and I have been looking into making antennas for 70 cm.
and higher frequencies, but we don't have an MFJ-269; my MFJ-259 tops
out at 175 MHz. I _do_, however, have an SWR meter that supposedly
works up to 500 MHz( and maybe higher), and an HP 8640B that is good
to about 1.2 GHz.

If the SWR meter is sensitive enough, could I get at least ballpark
SWR values using the 8640B as a source, running the signal through
the SWR meter to the antenna? Or am I way off in left field?

Mike-

I think you are on the right track with the RF log-amps.

Another idea - I understand the MFJ-259 has a standard SWR configuration
with a built-in signal source that uses an ALC to keep forward power at
the equivalent of full scale. Why not replace the 259 signal source
with the HP 8640B?

I hadn't thought of that. I suppose I could put a jack on the 259's
case, and a switch to select the 8640B, which has _marvelous_ ALC all
its own. The switch, and some RG-174, ought to be good enough for what
I'll be asking them to do. But that changes the question to "Is the
259's SWR sensor good enough above 175 MHz, and especially around 33
cm to 25 cm, to give real-world answers?"

I'll never know if I don't try.

I may have to buy a factory UHF-and-above antenna analyzer to validate
my answers, of course. I'm sure W5DNA will understand why we're eating
potato soup for two or three months.

Thanks!

--
Mike Andrews, W5EGO

Tired old sysadmin