I'm trying to set up a 160-m. Inverted L for ARRL-160 this weekend but am
having an interesting tuning problem. All thoughts appreciated!
The Inverted L is made up of #12 stranded copper wire 136' in total length:
82' vertical and 54' horizontal. The vertical wire is spaced 6' from a 88'
self-supporting tower with a Cushcraft XM-240 mounted on top. (XM-240 elements
are not grounded) Initial radial system is 2- 135' radials laying on the
ground- not much but two similar radials worked pretty well on my 60' tower
year as the towers are 150' from a salt water river.
Placing the Antenna Analyzer (AIM 4170) at the base of the Inverted L gets
the following measurements:
1) With the coax braid connected to the tower base which has two 8' ground
rods: lowest SWR is 3.9 at 1.776 Mhz and Z = 79.
2) With coax braid only connected to the two radials (and not the tower
base): lowest SWR is 1.62 at 1.614 Mhz and Z = 81.
It was my understanding that the coax braid should be connected to both the
radials and the base of the towers gnd system, but as you can see the the
minimum SWR and resonant freq. go crazy when I do.
Any recommendations what I can do to get it working before tmw night?
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