[TowerTalk] 160-m Inverted L or Sloper?

Tom Rauch w8ji at contesting.com
Mon Nov 14 19:13:42 EST 2005

> Well last year I put up an Inverted L (100' vertical, 70'
> with 20 full size radials on a separate tower and compared
> to my half slopers. I didn't do any transmit comparisons
but my receive
> comparisons were 2-3 S units down from the half sloper.

Right away Doug that's a big red flag. The average for S
meters in mid-scale is about 5dB, so that would be 10 to 15
dB. That's a signal ratio of 10 to 30 times. What that
really indictates is you had something wrong with the
Inverted L more than anything else.

 Admittedly I
> didn't do the comparison using good specific comparison
techniques for
> a technical report.  But my 'ballparking' comparison gave
me enough
> information to decide whether to continue the testing or
not.   My initial
> evaluation did not warrant further Inverted L testing.
The test
> configuration
> is still in place as I haven't taken it down yet.  Maybe I
will look at
> it again as we all know that you cannot have too many

Actually we can have too many antennas. Some of the poorest
performing installations I have seen are those with multiple
antennas jammed in a small area. This is especially true on
low bands, where antennas need to be hundreds of feet apart
to not interact.

Even the best method in the world won't provide reliable
results when antennas a fraction of a wavelength apart are

I can and have installed simple Inverted L's here, and a 70
foot high 1/4 wl long Inverted L with 50 radials was within
one dB  or so of my 200 ft insulated base tower with 100 200
ft radials. In Toledo Ohio K8GIJ on a small city lot was
always neck and neck with me, and I had a 130 ft vertical in
a swampy area of wet black dirt with a hundred radials. On
the other hand W8LNV had five times the back yard as Harold,
but Joe had it jammed with multiple antennas. Joe would
consistently be 10 dB and more down from Harold.

Even 4 element phased arrays with 1/4 wl elements can't beat
a properly 70 ft Inverted L by ten dB.

Something must have been wrong with the Inverted L.

73 Tom

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