[TowerTalk] re: CATV question

[Michael Lamb]

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From: 	Randy Lake[SMTP:rlake@monad.net]
Sent: 	Thursday, October 08, 1998 7:03 AM
To: 	towertalk@contesting.com
Subject: 	[TowerTalk] re: CATV question 

Randy:

I have been using .75 inch CATV cable for many years and never paid attention to the lengths.  I just thought I would accept the raise in SWR because it should only be about 1.5 : 1 increase.  I had a lot of problems getting the SWR on my triband stack down and so I finally went and got some Amidon 1.5:1 wideband UNUNs and put one at each end of the 75 ohm line.  That finally got my SWR down to a reasonable level and the stack seems to be very competitive again.  The Amidon UNUNs are nicely packaged and only claim to be good up to 40 MHz, but I placed one on the CIA analyzer and it showed only 1.2:1 with a calibrated 75 ohm load at 54 MHz.  I put it in line on one end of my 500 foot run on six meters and the SWR dropped from 1.6:1 down to 1.25:1.  I will put one up at the tower end soon!

It just seems to me that you might want to consider the easy way out that will bring your SWR down, regardless of the HF band you want to use the coax on.  I am so sold on them that now I am considering using open wire feedline in the future with 9:1 UNUNs in the line.  I can drop my losses on the 550 ft. run of coax to the triband tower almost an additional 1.5 dB!  That's like adding an additional 4 yagis to the six stack!

73/Mike, N7ML

I have approx. a 160' run of 3/4 CATV going to the tower. my question is this, the overall length of the run, should that include going from the back of the amplifier to the antenna? I have a 6' piece of 50 ohm going to my 75 hardline then back to 50 ohm rg213 to the th6 stack, approx 33' each.......I never once measured anything when I put this all together....I do get some off the wall swr readings...at the antennas it all looks good but once you get inside...yuk.......does the 50 ohm to 75 ohm back to 50ohm cause problems.....should i get rid of the CATV and get some 9913 or something similar for the whole thing?
Any thoughts?
Randy N1KWF
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