Do you know what frequency the 911 radios use? I'm guessing these are VHF 2way radios?
Closest thing I can think of that I've run into is customers who are also ham radio operators, or with OTA TV antennas and interference into low band VHF channels 2-7. I didn't have much luck with shielded cable or ferrites. The fix has been to change from 100M to 10M Ethernet. I assume you cannot do this. If the radios are GigE capable, you could experiment with forcing 100M or 1G Ethernet. I think once long ago I had a case where the interference was harmonics of the switching power supply in the POE brick, and changing it to a linear (transformer) brick helped. Probably not applicable in your case. -----Original Message----- From: AF <[email protected]> On Behalf Of [email protected] Sent: Thursday, February 28, 2019 4:21 PM To: AnimalFarm Microwave Users Group <[email protected]> Subject: Re: [AFMUG] Interference with 911 repeaters I would first attempt to discover if it is the CAT5 or the radio itself. Ask the 911 guys if they have a spectrum analyzer they can lend you to puzzle this out. Shielded CAT5 helps. Putting in coils at the ends helps. Ferrite chokes help. Some run it in liquidtight or full metal conduit. You can put fiber media converters on the ends of a CAT5 and perhaps fix it. But every single ethernet device, every switch, hub, router, radio does radiate noise. Just because they passed FCC certification tests does not mean they are noise free. The 911 repeater probably has a high gain omni and probably a super low noise pre amplifier too. So it will naturally be more sensitive to noise than a normal 2 way repeater. Isolating it to a particular radio or cable is a good place to start. -----Original Message----- From: Craig House Sent: Thursday, February 28, 2019 1:45 PM To: [email protected] Subject: [AFMUG] Interference with 911 repeaters > > I think I’ve posted this question on here before but I want to try again. > We have multiple water towers where we have various types of equipment a > mix of Mimosa cambium and ubiquity products. It seems that on many of > these water towers our cat five power over ethernet creates RF > interference for the repeater. In one instance we were able to install > magnets that clamped around the cable which did help enough they stopped > complaining. In other cases we’ve attempted to move our equipment from the > top of the water tower down to the catwalk to create some distance and > installed the ferrite beads with little success at all. I’m tired of > playing with ideas that might or might not work. Can someone give me > advice that will solve this problem once and for all. I understand that > grounding the CAT5 might help I’ve also been told that putting our wires > inside of conduit might help or shortening the wires might help. I don’t > want anymore might help I would like someone who has actually done this to > be able to give me some advice > > Sent from my iPhone -- AF mailing list [email protected] http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list [email protected] http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list [email protected] http://af.afmug.com/mailman/listinfo/af_af.afmug.com
