On Sun, 25 Apr 2010 15:29:20 -0700, JIMMIE wrote:

On Apr 25, 3:16Â*pm, Chuck Forsberg WA7KGX N2469R wrote:
I installed a Diamond X-200A antenna just above a Thunderbird TH5MK2
tribander. Â*Due to a short mast, the Diamond is virtually sitting on
top of the Thunderbird.

The lead-in consists of some 20 feet of 9914f and 50 feet of 9913,
connected with UHF connectors.

The measured SWR minimum is at 147.7 MHz and 1.2:1 at the far end of
the coax. Â*The MFJ 259B reads 1.9:1 at 144 mHz. Â*Presumably the SWR is
a bit higher at the antenna connector.

If I use a longer mast to raise the Diamond above the tribander, can I
expect the resonant point to move to the specified 146 MHz and the SWR
at 144 to go down? Â*How much separation is needed?

The 9913 is infamous for getting water inside of it. This is usally
indicated bu an unusually low and broad banded VSWR reading. There
should be some good info on the internet about "stacking antennas" I
think some of those who loiter on this NG have written some papers on
it, I seem to remember Owen but I may be wrong.

Jimmie

I checked the 9913 and discarded some of it where there had been a hint
of water ingress. In this instance, the SWR is a bit higher than Diamond
shows in its chart. The SWR minimum at first glance is no broader than
spec - it's just at the high end of the band instead of the middle.

Later this week I should know if separating it further from the Thunderbird
will change things.