W8BYA:
>I was wondering if someone could recommend an easy and elegant
method that would allow me to use a bunch of 7/8" 75 ohm hardline I have. My
antennas on 2 of 3 towers require over 270' runs and I would like to use this
very nice hardline. On VHF and UHF I built custom 1/4 wave transformers which
have worked perfect for years but for my tribander that approach will
obviously
not work. Any ideas?
Gedas you have the perfect length
for half-wave multiples of 75 ohm hardline.
I measured my 3/4" hardline Vf at 0.8711 and cut
it to 242.29' (8 wl on 10m, 6 wl on 15m and 4 wl
on 20m). You could also use this on 40-160 since
it is 2 wl on 40, 1 wl on 80 and 0.5 wl on 160.
I was curious about the bandwidth of the
hardline itself, so I terminated it with a 50
ohm non-inductive load and measured the 1.5:1
bandwidth of the feedline alone as follows
using an MFJ-259B (which I also used to fine
tune resonance at 28290 kHz and sub-multiples):
27735-28990 kHz
20877-21670
13820-14546
6738-7439
3204-3900
FLAT ON 160
Measured loss (MFJ-259B):
28.3 - 0.4 dB
21.2 - 0.4
14.14 - 0.3
7.070 - 0.2
3.535 - 0.1
1.768 - 0.1
Free hardline and nearly free connectors
(pipe reducers and barrel connectors) makes for
easy, elegant and inexpensive! For the remaining
~30' of your 270' run, simply use 50 ohm coax.
73, Bill W4ZV
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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