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Old 4th September 2012, 08:22 PM   #11
john57 is offline john57  United States
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What is the source connected to the TV? I had a problem with ground loops coming from the cable TV coming into the house. If your are using cable you can temporarily disconnect the cable and see if the problem goes away.
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Old 4th September 2012, 08:31 PM   #12
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Well, while BBC Wiltshire bangs out timeless gems, such as Eye of the Tiger, followed by Pass the Dutchie, I've bypassed the nicely-clipped-to-skirting-board 10m ethernet cable with a bundled-mess-that-was-recently-a-coil 20m ethernet cable, and the glorious local content is still there, but far quieter. I assumed the 20m would pick up more, but I guess the inductance from the coiling is acting as a ferrite would.
So, I hope this can be fixed with ferrites and shielding (if needs be).
Hopefully can fix the issue faster than Steve Miller can say Abracadabra!
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Old 4th September 2012, 08:33 PM   #13
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Hi John,
The TV is fed by just an aerial - and a STB and PS3 both connected to the network (although the STB is currently disconnected).
Cheers,
Phil
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Old 4th September 2012, 09:29 PM   #14
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Does it disappear when you unplug the aerial from the TV? If so, the TV aerial cable will be a good place to try the ferrite ring.
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Old 5th September 2012, 07:18 AM   #15
marce is offline marce  United Kingdom
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Shielded ethernet, ie CAT 6 or CAT 7
At least youve saved on a receiver
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Old 5th September 2012, 08:42 PM   #16
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Hi Don,

Unplugging the aerial doesn't seem to help. Ho hum.
Hopefully the ferrites will arrive soon, and I can try them out.
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Old 28th September 2012, 06:14 PM   #17
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So, I've tried ferrites and cat6, and have discovered the radio is still audible. I have also noticed with just a run between the hub and the mac (nothing else plugged into the hub) it is still there.
Alas, I've since used a different amp, and although very noisy, it's not picking up radio wiltshire. So it seems, somehow, if my JLH is plugged into a network device, it can receiver radio. Oh the joys of grounding issues!
Some further diagnosis has occurred, and more info has been gleaned, but still no closer to the problem.
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Old 28th September 2012, 06:27 PM   #18
john57 is offline john57  United States
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One more thing I can think of is cold solder joints inside the unit. I used to built Heathkits when I was a kid and had issues with noise caused by cold solder joints. It seems that you covered many things.
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Old 28th September 2012, 06:28 PM   #19
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I did some checking up on cat 5 cables and I noticed that only 4 of the 8 wires are used for up to 100mbit and all 8 are used for 1000mbit or giabit ethernet. So if you have some spare cable you can try to cut out the remaing 4 wires.

When disimilar metals make contact they can cause corosion and perhaps make a diode detector for the AM radio that you are picking up. Have you tried cleaning all contacts?

There is a military base near where I used to live and they used to broadcast to the troops overseas and when they uses a particular frequency at a certain time of the day I used to be able to hear the broadcasts through the Moving Coil preamp. A real PITA when I was trying to record to cassette tape for the car. Switching to MM solved that issue.
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Old 28th September 2012, 07:07 PM   #20
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Thanks for the ideas multisync.

I've finally made the break through!
I've noticed the main heatsinks weren't grounded. Some simple strapping with crocodile clips and all was solved!
I admit, they need proper earthing for safety (edit) purposes - which was going to happen, but I'm amazed how, when working with a LAN device they behaved as such an efficient antenna for a very exact frequency (without any drifting!).
If I tried to deliberately build an aerial for these purposes, I know I would fail!

What a saga!
Off to find a drill, nuts and bolts, and lugs....

Thanks for everyone's help!
Everyone. Ground your heatsinks dammit!!

Last edited by philpoole; 28th September 2012 at 07:12 PM.
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