[TowerTalk] Using 75 Ohm Hardline

[Gedas]

Wow, what great responses from so many on and off-line.  Thank you all those who helped think this through.  As I mentioned in the original post, I have been using the cable for VHF/UHF for some time and don't have any problems making up the ends to be PL-259 or N-connectors. I seal the ends with a tight wrap of electrical tape then apply a thick layer of outdoor grade Silicon RTV. What's great about the RTV is, that if needed, it can be peeled off in just a few minutes. I have had connections like this outside for years so far without any signs of degradation even at 70cm.

But, regarding the mismatch between 50 and 75 ohms, if on all bands my antenna were a 1:1 (at 50 ohms) I would not have worried about the immediate jump to 1.5:1 or the extra loss created by such.  My antenna at best is around 1.5:1 and near the band edges gets higher than that.  My concern was the added SWR to this when using the 75 ohm cable.  I do not own a high power tuner and just purchased a legal limit amp and do not want to experiment tuning it into a possibly high SWR. My rig of course has a built in tuner so lower power operation would have been no problem.

I had considered the 1/2-wave principal early on but did not take it far enough.  I considered a 1/2-wave working on 20m and on 10m but not on 15m. However, as several had mentioned, if the cable is made longer, like when the primary frequency is made to be 40m or lower, then all three bands can be made happy.  That's the trick I was looking for.  I want to thank everyone for taking the time to share thoughts and ideas.....this is a great group of people !!!

Hope to see you on the air soon. Oh, BTW, found the problem with the HAM-IV rotor.....I faulty limit switch.  Rotor is back together and soon to go up the tower.  I should be QRV this afternoon.
73,
Gedas, W8BYA
 
e-mail  w8bya at mchsi.com
online gallery  http://gedas.cc
web page  http://www.w8bya.com

----- Original Message ----- 
From: David Robbins K1TTT 
To: towertalk at contesting.com 
Sent: Sunday, June 05, 2005 6:03 AM
Subject: Re: [TowerTalk] Using 75 Ohm Hardline


First, forget the impedance mismatch, for hf use it is absolutely
insignificant.  Then follow the comments some others have made about using
plumbing fittings to make your own connectors, cover them with lots of duct
seal available cheap at the same hardware stores and enjoy them for years to
come.


David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
 

> -----Original Message-----
> From: towertalk-bounces at contesting.com [mailto:towertalk-
> bounces at contesting.com] On Behalf Of Gedas
> Sent: Sunday, June 05, 2005 01:29
> To: towertalk at contesting.com
> Subject: [TowerTalk] Using 75 Ohm Hardline
> 
> Hi everyone. 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?
> 
> 73,
> Gedas, W8BYA
> 
> online image gallery at  http://gedas.cc
> e-mail address at  w8bya at w8bya.com
> web page at  http://www.w8bya.com
> _______________________________________________
> 
> 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.
> 
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk

_______________________________________________

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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