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LMR Feedline for Will Burt Mast

This forum is dedicated to helping people with questions about installing radio equipment in vehicles. This can include antenna installs, electrical wiring questions/problems, and mounting systems. Pictures of installs are welcome.

Note: Discussions regarding lighting, sirens, and other equipment now has its own forum in the 'off-topic' section below.

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a1emt
Posts: 82
Joined: Thu Jan 02, 2003 7:44 am

LMR Feedline for Will Burt Mast

Postby a1emt » Fri May 26, 2017 6:56 am

I am working with a Will Burt pneumatic mast for the first time. Installing a portable UHF repeater in a trailer with a 20' mast attached.

Looking for recommendations on what the best feedline to use in this installation. The repeater will be in the 462.xxxx MHz range operating at low power (10-25 watts) through a Celwave flat pack duplexer. Sounds like the user will be removing the antenna and feedline from the mast when traveling. Would like something that is relatively flexible for ease of deployment and the ability to coil around the mast as it is extended.

Anyone have experience with such an animal?

jsilberberg
Posts: 39
Joined: Wed Sep 28, 2005 1:55 pm

Re: LMR Feedline for Will Burt Mast

Postby jsilberberg » Mon May 29, 2017 6:45 am

So to begin with, the answer for cable management is usually Nycoil when dealing with Wilburt masts, either through them as part of the package or independently -- . http://www.willburt.com/products/access ... anagement/

But the more important question here is what is the loss calculation you can live with. 100 Watts in could be 1 Watt out with is probably not acceptable. So get out a an excel workbook and put in the losses and add them up to see what works. I have often seem LMR 400 Flex used in this style deployment due to it's loss characteristics in UHF. Times Microwave has some good charts to help and be sure to include your duplex and and any jumpers in you calculations.. http://www.timesmicrowave.com/cms/tech- ... lculators/

Good Luck --
J. Silberberg
CompuDesigns, Inc.
Atlanta, GA.

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a1emt
Posts: 82
Joined: Thu Jan 02, 2003 7:44 am

Re: LMR Feedline for Will Burt Mast

Postby a1emt » Tue May 30, 2017 5:06 am

Thanks for the link to the Nycoil product. That was what I was envisioning, but I don't think it is going to fit into my customer's budget for the project. LMR400 flex may be the ticket, but as you said, I will crunch some numbers to see what the loss turns out to be. Thanks for your reply!

Jim

resqroz
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Joined: Mon Jan 28, 2008 5:49 am

Re: LMR Feedline for Will Burt Mast

Postby resqroz » Tue Jun 06, 2017 5:59 am

I maintain a lot of TV trucks that have WillBurt masts. I use LMR Ultraflex in Nycoils. If the person is going to deploy this a lot it would be much more secure to spend the extra money and use the Nycoil for protection.

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motorola_otaku
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What radios do you own?: 2 turntables and a microphone

Re: LMR Feedline for Will Burt Mast

Postby motorola_otaku » Thu Jun 29, 2017 11:56 am

Loss at 20' of LMR400 is more than acceptable for a GMRS repeater.

Ideally you would leave the cable attached to the mast and trailer, and take it into a N bulkhead connector at the top of the mast that the antenna would connect to. The best setups I've seen took the Nycoil into a weatherproof box with mil-spec weatherproof Cat5e and N bulkhead connectors on the box for antennas and IP devices.
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