Cabling recommendations for 25' dual runs from modem to LTE antenna

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rwidebrook
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Joined: Tue Aug 27, 2019 7:01 pm

Cabling recommendations for 25' dual runs from modem to LTE antenna

Post by rwidebrook » Tue Oct 01, 2019 9:19 pm

Hi everyone. I've got my first build/use of "fixed wireless internet" equipment, namely the WE826-T2 + MC7455 in stock form. My question here involves choosing a 50 ohm cable for a proposed 25' run from modem to rooftop LTE antenna. I'd like to hear your experiences and recommendations.

I get "just fair" 4~5Mps download speed in a Sprint fringe/roaming zone, by optimizing placement of the modem and its standard 3dB rubber antennae. The modem usually is operating on Band B41, with "not bad" at!gstatus? results, so a good antenna+cable setup seems a natural next step.

25 feet isn't such a long run, but I'd like to balance my choice of a suitable low-loss cable between performance and price. I'm leaning toward 5D-FB or LMR-240 due to their good attenuation specifications. I've eliminated RG-58 and RG-174 as being lower performance, and LRM400 as being overkill. Here's one interest: https://www.amazon.com/gp/product/B07JP ... SQKY&psc=1

What experiences and recommendations do you have?
Thanks, Rick

swwifty
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Joined: Thu Aug 30, 2018 8:21 pm
Location: NE GA Mountains

Re: Cabling recommendations for 25' dual runs from modem to LTE antenna

Post by swwifty » Thu Oct 03, 2019 2:36 pm

You most definitely don't want to skimp on cheap cable. Especially if you are going through all the effort of running it to the roof.

I did some quick calculations and on Band 41 (2500mhz) LMR 400 only loses about 2db of signal for 25ft.

That 5D-FB (which i've never heard of) best I can find loses about 3db of signal for 25ft. I'm not 100% sure that is right, but it's what i found online.

I'd go with LMR400. I have two 10ft runs of it on my roof and don't regret the extra expense after all the work I went through to get it up there.

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terryjett
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Location: West Tawakoni

Re: Cabling recommendations for 25' dual runs from modem to LTE antenna

Post by terryjett » Fri Nov 01, 2019 3:10 pm

In 100% agreement with @swwifty. Don't skimp on your cable. Just an extra loss of 1 or 2db can make a world of difference if you are on the fringe.

This calculator gives you good idea of different cables: https://www.qsl.net/co8tw/Coax_Calculator.htm

LMR-240 @ 2500MHz = 3.234DB for 25ft
LMR-400 @ 2500MHz = 1.695DB for 25ft

Keep in mind that all calculators will give you different results since they are based on a specific manufacture or maybe just a general calculation.

Do not see a big selection of cable in LTEFix store:( Do a search for amazon for "LMR-400 25ft N-Type Connector" (or whatever connector your need).

swwifty
Posts: 508
Joined: Thu Aug 30, 2018 8:21 pm
Location: NE GA Mountains

Re: Cabling recommendations for 25' dual runs from modem to LTE antenna

Post by swwifty » Fri Nov 01, 2019 7:09 pm

Another thing that is very important with cable loss to keep in mind is, you lose transmit power as well, not just received signal strength.

Let's say you lose 3 db of signal in your cable (keep in mind this is 50%). That works both ways, so you're 23dbm (max transmit power for a LTE modem) just turned into 20dbm, doesn't sound like much, but you lost half your power. Which could be the difference between the tower hearing your modem well or not. Essentially it could effect your upload speed as well. Something to keep in mind.

HazelOvElt
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Joined: Mon Sep 09, 2019 7:24 pm

Cabling recommendations for 25 dual runs from modem to LTE antenna

Post by HazelOvElt » Sun Nov 10, 2019 9:16 am

I avoid the attic at all costs. Since you are QRP, there are other options. From mag loops, to shortened dipoles, etc.

Search Google again, they are there.

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