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Posted: 6/22/2011 10:07:07 AM EDT
I recently started noticing a fast "choppy" interference on my radio. Through the process of elimination I narrowed it down to a recently installed security camera. The camera is an Axis FD216, IP camera, that is connected to the computer by a CAT 5e cable. It is also gets its Power Over Ethernet (POE) from a TP-Link 8 port router.

When I disconnect the camera cable from the router, the interference stops. When I plug it back in, it starts up again and the interference matches the flashing from the ethernet port on the back of the camera.



Would shielded CAT 5 cable stop this?

If so, where's a good place to buy it?



TX




Link Posted: 6/22/2011 10:21:44 AM EDT
[#1]
Without trying the usual "reposition stuff" option, I would recommend shielded coax.  Can't make a recommendation on where to get it, but it should be plentiful.  I would look at NewEgg.com, TigerDirect.com, or CDW.com.
Link Posted: 6/22/2011 11:01:37 AM EDT
[#2]
It's a long shot but you could try plugging the router into a different outlet.  For no more time than it would take it's worth a try.  
Link Posted: 6/22/2011 11:59:58 AM EDT
[#3]
Also, if it is at all possible, you might try a cat6 cable. Cat6 cable has a spine running the length of it that keeps the twisted pairs a bit more separated than in 5 or 5e. This cuts down on crosstalk. As an added benefit, not sure you might need this or not, the spine gives the cable a robustness that 5 or 5e lack. I don't have any experience with shielded cat6, however, from working in audio for many years, I would guess that it would make a difference. I also think that the shield should only be grounded from one end, though.

If you supply power to the unit locally, instead of PoE, does the interference go away?

ETA, the jack you plug a shielded cat6 cable to would also have to have its shielding tied to ground if you expect the shield on the cable to have continuity with ground. I'm not sure all jacks have this option/provision.
Link Posted: 6/22/2011 1:27:22 PM EDT
[#4]
It's not the cable, it's the switch.

I've tried several desktop switches in my office at work and ALL of them put out massive (S7-S8) RFI, affecting my lowly little HT and VHF/UHF reception. Being a geek, I just wired up a few extra ports to a wall plate in the office and 86'd the switch... problem solved, plus now I have all Gigabit, all the time.

The only cure is to swap out switches until you find one decently shielded (unlikely IMHO) or try to get as much separation between the switch and the radios, or unplug it.
Link Posted: 6/22/2011 7:08:04 PM EDT
[#5]
Quoted:
The only cure is to swap out switches until you find one decently shielded (unlikely IMHO) or try to get as much separation between the switch and the radios, or unplug it.


You could also shield your existing switch - Re-mount it in an RF-tight metal enclosure, mount filtered RJ connectors on it, use feedthrough caps and ferrite beads for the power supply wires, etc.

It's sometimes also possible to tack some extra bypassing on to the circuit board itself.
Link Posted: 6/22/2011 7:14:12 PM EDT
[#6]
Quoted:
I recently started noticing a fast "choppy" interference on my radio. Through the process of elimination I narrowed it down to a recently installed security camera. The camera is an Axis FD216, IP camera, that is connected to the computer by a CAT 5e cable. It is also gets its Power Over Ethernet (POE) from a TP-Link 8 port router.
When I disconnect the camera cable from the router, the interference stops. When I plug it back in, it starts up again and the interference matches the flashing from the ethernet port on the back of the camera.

Would shielded CAT 5 cable stop this?
If so, where's a good place to buy it?

TX




What frequency[s] does the interference show up at?

This will give many clues how to eliminate it.



Link Posted: 6/22/2011 7:42:37 PM EDT
[#7]
Quoted:
What frequency[s] does the interference show up at?

Although likely you'll need to either replace the switch or else attenuate the RF garbage it's spewing by some combination of choking/ferrites on connected wiring, case shielding, or inside-case noise suppression.
Link Posted: 6/23/2011 2:21:28 AM EDT
[#8]
Good thread. I have been working with the same problem as I just picked up an HDMI cable that does this. It puts out so much RFI that my VX7 is unusable within 20ft. It even makes my HT1000 break squelch from time to time.
Link Posted: 6/23/2011 5:00:49 AM EDT
[#9]
I tried a CAT6 cable and a lot of the "chop" disappeared, but I could still hear the digital signal.

I then powered the camera by the wall wart and plugged the net cable into my main wireless router and most of the chop came back.



I'm going to try a shielded CAT6 cable next to see if that solves the problem....




Link Posted: 6/23/2011 5:27:10 AM EDT
[#10]
I keep a drawer full of those clamp-on ferrites for this sort of thing. Every time I order from all-electronics, I get a few more. I once had to put them all over a PC power supply to quiet it down. Looked funny, but it's inside the case and it worked!

GL, Eric
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