We're on about a dozen FM sites. Most are 3-6kW ERP, 1-3kW Tx. No issues
on those. And then one 50kW ERP, 17kW Tx. No major issues, just some CRC
errors. Got a 450 cluster here. The ethernet links have been up for 194
days and only two of the radios are showing about 3000 CRC errors.
That's about 265 feet of Shireen shielded cat5e, too. No ferrites, just
Rev B GigE-SS-HVs. I did discover that if I disconnect the ground from
the PRM24, the errors do tick up a bit. So.. something is doing...
something.
Which brings me to... the worst mistake you can make on an FM or a VHF
2-way site is not making sure everyone is following the single-point
bonding principle. Everything from surges to common mode RF on the
shields of coax and cat5. Been there, done that.
That 50kW site has an old transmitter. They don't want to replace it
because they say it "sounds good" to them. They have some big copper can
thing between the transmitter and the transition to the transmission
line. I have no idea what that's for, but I imagine some kind of filter.
On 9/17/2017 10:21 AM, Adam Moffett wrote:
It might do nothing to you.
The most crippling problem we saw was colo with a 35,000 Watt FM
station. The only thing that fixed that was fiber to a box at the
top, and then shielded CAT5 jumpers as short as possible to the AP's.
In other FM radio cases shielded cable alone was enough, even when
their antenna was pretty close to our AP's. One case was fixed with a
huge ferrite core with the cable looped through it a bunch of times.
------ Original Message ------
From: "Jon Langeler" <[email protected]>
To: [email protected]
Sent: 9/16/2017 3:13:52 PM
Subject: [AFMUG] FM radio colocation interference?
Theres a potentially new FM radio tenant wanting to colocate on a
tower we are already on. We're predicting there is absolutely no way
this will work with our 100BT and 1000BT Ethernet links.
He anyone collocated with FM radio and 'it worked '?
Jon Langeler
Michwave Technologies, Inc.
