Always good to use shielded. Three types of shielding:
1) Electrostatic Shield grounded at one end.
2) Magnetic Shield grounded at both ends.
3) Faraday Shield not grounded but present.
Then there are chokes to prevent the RF from traveling on the surface of the
cable conductors and shield conductors. That is probably the problem. You
add inductance.
You do that my making a coil out of the cable. Like 5 turns of CAT5 on a 5
inch diameter circle. Just coiling it up chokes the FM frequencies from
continuing.
Add ferrite split cores around the CAT5. Does pretty much the same as a
choke coil. Maybe better.
You have to buy the ferrite for the frequencies you are trying to choke.
You might be able to also choke it out by putting a POE injector in line or
even two, one at each end. If you don't need poe on the line a POE injector
will block longitudinal signals like this.
-----Original Message-----
From: Nate Burke
Sent: Friday, July 20, 2018 11:45 AM
To: [email protected]
Subject: Re: [AFMUG] Ethernet problems next to FM Antenna
Do you have to use unshielded cat5 if you put a core or choke on?
On 7/20/2018 12:02 PM, [email protected] wrote:
Ferrite beads/cores around the cat5 as well as choke coils of cat5 seemed
to help many with this problem.
-----Original Message----- From: Nate Burke
Sent: Friday, July 20, 2018 10:31 AM
To: Animal Farm
Subject: [AFMUG] Ethernet problems next to FM Antenna
It looks like the old archives aren't back online yet, so I couldn't go
searching through there for ideas.
I have a site where we have been co-locating with a 800w FM Transmitter
for years. We've always had Ethernet problems at the site since the FM
went in. Everything is shielded cat5 (Belden 7919). It is at a grain
elevator, our equipment is on one corner of the platform, and the FM
Transmitter is on the other corner. We are horizontally separated by
about 10 feet. There is no way to get vertical separation. I used to
run all the cables down to the bottom of the leg, about 100'. In an
effort to make the Ethernet work better, I installed an Edgepoint fed
with Fiber at the top, so cable lengths between the radios and the
Edgepoint are now 5'-10'. With the FM Transmitter turned off, everything
runs perfectly. When the FM is turned on, most equipment drops to
100mb, and some goes down to 10mb. On the most problematic equipment, I
have installed the 4 pair FM Filters from Sandman
http://www.sandman.com/rf.html within 12" of both the switch and the
radio. It made no change.
What FM Elimination tricks have I forgotten to try? I was really
expecting the short cable lengths to solve the problem.
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