Cat5 Cable Noise on Tower

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Birken Vogt
Posts: 262
Joined: Thu Nov 10, 2005 7:53 pm

Cat5 Cable Noise on Tower

Post by Birken Vogt »

With WISPs everywhere, we run into this problem from time to time. When they are above our rx antenna, the Cat5 cable will frequently be radiating enough noise to seriously degrade the rx.

There have been some hillbilly solutions we have tried such as running the cable inside EMT conduit where it passes the antenna, but I have my reservations about that with extra joints and potential loose hardware on the tower.

One thing I have recently considered would be the underground Cat5 that has an overall corrugated copper shield that looks like hardline. This shield is only overlapping at the ends and not a solid pipe like hardline which makes me wonder about its efficaciousness. Not sure about terminating the end(s) either.

Any words of wisdom here?
jry
Posts: 481
Joined: Fri Feb 06, 2004 3:14 pm

Re: Cat5 Cable Noise on Tower

Post by jry »

you know I would run optical ( Multi Mode FIbre should work if the distance is not too long OM4 a plus)...not sure they have an SFP port instead of copper ethernet ports( RJ45) but this would have a number of advantages.

1. should fix your noise issue
2. more reliable especially outside over distance
3. no ground loops at least from that cable.

1Gbe SR SFP's are pretty cheap these days so not a massive expense. 10Gbe SR is not too bad either .

It's the LR SFP's that tend to get pricey and need single mode fibre cable as well.

Just a thought ...may not work in your context depending on the HW they use.
Birken Vogt
Posts: 262
Joined: Thu Nov 10, 2005 7:53 pm

Re: Cat5 Cable Noise on Tower

Post by Birken Vogt »

More often than not, the WISP is the 800 lb gorilla. We are attempting to take care of the little volunteer fire departments.

We can ask the WISP nicely to behave themselves, but the site owner collects rent from them and usually next to nothing from the VFD. So we have to develop some sort of mitigation for copper ethernet cables.

But indeed thank you for the clue on the fiber. Not being IT people we are not keeping on top of the latest and greatest. We do have to renegotiate some sites that are more 2 way oriented with WISPs there as well. I think we will specify that all runs on tower must be fiber from here on. (Or coax cable IF for MW that way too)
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Astro Spectra
Posts: 668
Joined: Sat Sep 22, 2001 4:00 pm

Re: Cat5 Cable Noise on Tower

Post by Astro Spectra »

There have been a few threads on this in the past here.

First thing to do is have all the cable runs replaced with top quality outdoorcrated shielded Cat 5/6 cable. Like the Tough Cable from Ubiquity.

You can explain to the WISP that it's better for them (reduces chances of induced lightning damage and less chance of RFI from you) and that it not unusual to do this at shared RF sites. Explain that if Ubiquity sell and recommend the cable it must be good for WISP use as that's maybe 75% of their business.

Next you need to treat the outdoor plastic cased RF units as they radiate at VHF. You can try RF Armor (expensive) or zinc rich spray from a can. Don't spray over the feeder section of the ODU obviously.
jry
Posts: 481
Joined: Fri Feb 06, 2004 3:14 pm

Re: Cat5 Cable Noise on Tower

Post by jry »

really surprised that they do not use fibre for this out of the box.
Nothing new here ...just standard networking stuff for decades.

Not really all that expensive in most cases.

The usual rule on fibre is you never run just one pair in that situation ...there is often breakage during the install so typically a multi pair bundle is installed so that you have spares.

You can order custom lengths and have the connectors installed and tested ...we often do that even in the data centers for trunk runs between major pieces of equipment
Jim202
Posts: 3609
Joined: Sun Sep 09, 2001 4:00 pm

Re: Cat5 Cable Noise on Tower

Post by Jim202 »

This is not a really new problem and it has killed a bunch of low band service users including the 6 meter ham band. The real issue is with the tower owner for not having any restrictions of using ordinary CAT5 cable. Not grounding equipment racks and noisy routers being used. This is just the start of the noise problem.

I would suggest sitting down with the land lord and have some good back and forth discussions. If your dealing with one of the stubborn tower rental companies, good luck. It took me over 9 months to negotiate a lease contract for a public safety agency with one and that only happened after contacting one of the vice presidents. The sales agent just didn't have a clue what he was doing or could even care about the time he was taking.

Some of these nation wide tower rental companies are a real pain in the butt to deal with.

Jim
Birken Vogt
Posts: 262
Joined: Thu Nov 10, 2005 7:53 pm

Re: Cat5 Cable Noise on Tower

Post by Birken Vogt »

Thanks for the suggestions thus far.

I suppose for Cat5/6 stuff, the aluminum shield/drain wire stuff "should" be just as good as the copper/steel stuff and much easier (more normal) to work with.

We are taking over this system from another vendor and our little VFD customer is not the top billing on some of these sites. So we can ask nicely, but beyond that we will have to see where it gets us.
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