[TowerTalk] Inverted L Tuning Question

[Tom Osborne]

Hi Dick

You can get some screwy readings if there is a BC station nearby.  I can't 
even use my analyzer here on my 160 inverted L because of RF from the local. 
I have to use the SWR bridge in the shack.  73
Tom W7WHy



> Hi Guys,
>
> 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 last
> 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?
>
> 73,
> Dick- K9OM