Ethernet near FM antenna on tower having problems

Gotta watch those Fresnel zones!
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steveschuh
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Joined: Thu Dec 16, 2010 3:36 pm

Ethernet near FM antenna on tower having problems

Post by steveschuh »

I have some Cambium gear on a tower carrying PTP network between several other towers. On this particular tower my cable is running down past three different translator antennas. I have the Ethernet set to auto negotiate and it ends up slowing way down to 10 MHz speed. I'm using Superior Essex BBDGE CAT5e cable which has a corrugated solid copper shield. At this time I have the shield grounded at the tower base. I have seen this problem mentioned on forums from Cambium, Ubiquiti, and Mikrotik. There is some recommendations to wrap the cable in ferrite filters. I am bringing the discussion to this site to see what radio engineers can share about this problem. Thanks
TPT
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Re: Ethernet near FM antenna on tower having problems

Post by TPT »

Anyplace on the equipment to ground the top end of the cable?
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kkiddkkidd
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Re: Ethernet near FM antenna on tower having problems

Post by kkiddkkidd »

I have put UBNT dishes on a number of AM and FM towers and they are all different... I always try to ground at the top and bottom and as possible at other places along the cable.

With all that said, I had a client with Cambium radios that would slow to a crawl and eventually disconnect when the wind blew. It had common Cat5 that was changed to shielded Cat5 with little to no improvement. We later found out the shield wasn't grounded to the tower but not sure if it would have mattered.

The cambium radio and dish was about 3oft below the bottom FM bay of an 18kw DA 8bay. Turning the FM TX off would usually allow the radios to reconnect but sometimes not. The network would come back up as soon as it either started raining or the wind abated. We finally installed a cable similar to what you posted (rodent proof... copper shield) in some spare conduit that our tower crew had laying around and the problem was cured. I think that the copper jacketed cable would have been OK by itself but we had the conduit available cheap and wanted to beat it into submission once and for all.

We could only surmise that the cable was gathering static that caused the radios to puke up a byte.

Good luck,
--
Kevin C. Kidd CSRE/AMD
WD4RAT
AM Ground Systems Company
http://www.amgroundsystems.com
KK Broadcast Engineering
http://www.kkbc.com
steveschuh
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Joined: Thu Dec 16, 2010 3:36 pm

Re: Ethernet near FM antenna on tower having problems

Post by steveschuh »

The cable isn't grounded at the top yet. Tower crew had split before the job was done this summer due to bad weather. I put the ground kit at the base but when the crew returns we will try more grounding. There is a SFP port on this radio but I hate to go to the trouble of adding fiber. Conduit might be a better alternative.
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davek
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Re: Ethernet near FM antenna on tower having problems

Post by davek »

How long is the Cat5 cable run?
steveschuh
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Re: Ethernet near FM antenna on tower having problems

Post by steveschuh »

Cable run is about 225 Ft.
Kelly
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Re: Ethernet near FM antenna on tower having problems

Post by Kelly »

I would try the torroid trick. Get some 2" ferrite doughnuts and wrap as much cable through and around it that you're able, keeping the cable close to the ferrite material. May have to do one at each end.
Skype:kellyalford Twitter: @KellyAlford
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