Ian,
As some others have pointed out, I too have seen a little odd response
from the MFJ analyzer too. I very recently used one to toy around with
several DB420 antennas. The MFJ wasn't "wrong" really, but it did not
give the same response that two different SWR/Wattmeters powered by
two different transmitters did (the Wattmeter SWR combos always
matched). BTW: All of my testing was at the antenna feed point.
In the end, reflected power at the transmitter and how well the system
works in the real world are what are most important to me, but since
you have real-world problems, jumping to the antenna in an attempt to
start at one and and work your way back is the right thing to do.
73 DE N0MJS
On Sep 5, 2008, at 8:43 AM, Ian Miller wrote:
Our group has a Sinclair 8 dipole array for UHF.
The repeater was recently moved, and has not been behaving as usual.
It hears OK, but seems weak on transmit.
One of the members went up to the site last night with an MFJ antenna
analyser - and he measured SWR at 3:1 - with no real resonant point.
Our old UHF beam that was on the same tower and same feedline had an
SWR of 1.5:1 measured on the same analyser.
Is this method of measurement on an 8 dipole antenna correct? We
have not put an SWR bridge on it.
For the moment the repeater is off the air until the antenna question
is resolved.
What is inside the guts of one of those 8-bay antennas? Do they have
a weak point where a bad connection can occur?
Thanks
Ian
VA2IR
--
Cort Buffington
H: +1-785-838-3034
M: +1-785-865-7206
