atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Cabling Telephones Systems Wiring buzzing induced on analog phone system

I have an outbuilding with direct bury cat-5 cable connecting the outbuilding to the main-building.The
distance of the run is about 630ft. We are using a Panasonic KX-TG9582G Dect 6.0 wireless system in the main-building and have AT&T wired hand-sets in the out-building.

Whenever this wire is punched down into the 66 block with the rest of the extensions, we get an audible buzz on the line from any extension in the main-building and the outbuilding. I thought it may be grounding related, but i am not sure.

I tested continuity of the pairs and there is no cross wired or shorts between the pairs and i tried different pairs with the same result.

Any help would be appreciated!

Bob

Is your direct buried cable sheathed and is it grounded? You're saying buzz, AC hum or buzz? My guess would be AC power induction.

the AC Power is run 2ft deep - the direct bury is only about 1ft under the surface.
The cable is not grounded. Not sheithed either - just direct bury cat-5
If it is AC induced, not sure how i would correct that.

Without it having a conductive sheath you can't. Don't know how it can be called direct buried without a sheath. Rebury with the correct type of cable and give more clearance from the power if that's what you decide. Running parallel to power is never a good idea even with a good sheath, especially that distance. You could try grounding all the unused pairs, don't know if that would do it or not worth a try.

ok - i will try the grounding of the unused pairs. Thank you!

Are you sure you're using the correct white and the correct blue* to form the pair that is in use? If not, then you're using a split pair, which causes imbalance. Even without the AC power proximity, 630' of an unbalanced pair will pick up all kinds of noise, even nearby radio broadcasts!

* Or any other base color.

Many manufacturers of OSP cable, even drop wire, do not include a tracer mark on the whites to identify their matching base color forming a pair. You may be using the white that goes with the white/brown pair (or any of the others). Yes, it will work, but it will be noisy. You said that you checked for continuity on all pairs, but that just means that <a> blue and <a> white make it through.

Lastly, some Bell companies in the Southwest bury non-shielded drop wire due to their arid climates and soils, but that's the exception, not the norm. I've seen direct-burial CAT5e cable both in shielded and non-shielded varieties, but the shield is more of a copper foil. Regardless, grounding is NOT your issue. most ground faults on a working pair will cause all kinds of trouble, not just hum.

Ed, i have tried all 4 pair - same low level buzzing. I agree, i don't think it's AC induced. I thought the whole point of twisted pair was to reduce induced noise. Is there any type of filter or balancing device i could add to the circuit to help reduce the noise?

Shielded, that's the word I was looking for. Hell to get old. Ed, I don't think the OP's talking about a ground fault, he's talking about the drop not being grounded because there's no shield. I'm still betting on AC power induction.

i do believe there is foil wrap around the 4 twisted pairs. Maybe i should try grounding the shield? Have not had a chance to try grounding the non active pairs.

Couple of thoughts:

1) Ground the shield on one end only (you probably already know that).
2) Bill asked about the type of noise: would you know a 60-cycle hum if you heard it? That would be a clue.
3) One last thought is to disconnect your cable and walk the run with a wand/probe to see if the noise follows the whole path or if it is isolated to one area.

It's not 60cycle - i delt with that crap when i played in a band and had to chase down ground loops and other annoying noise in the guitar amps.
Will try all that is suggested - we got 70inches of snow on the ground here where i live so i doubt i will be doing the trace walk until next June!

I'm guessing that the original loop doesn't like the extra 600-700 feet of cable tied to it. It gives you a chance for an extra antenna. Try connecting only the remote building to the line and listen for background noise. If it goes away, your solution might be a small phone system where you are feeding an extension to the remote building.

For fun, you could do some research on bridge lifters here

In the C.O. days, we used to use them on party lines. It was great for hanging 4 separate cables on the same line, or an answering service to the customer's main number. Bridge lifters are probably made of unobtainium, but somewhere I have a single unit that weighs a lot and does such a feature. It may show up in the next 2 months.


Carl

So, what happens when you kill the power to the outbuilding? I can tell you from experience AC power induction isn't always a 60hz hum, I've heard buzzing, clicking and different harmonics on induction. It was a pretty big issue in the sandhills as you can't always get a good ground.

i tried grounding the un-used pairs - no difference - just a low level buzz/hum that is audible on both ends of the conversation. I will try killing the power in the out building next.

What would a guy recommend for getting phone signal to out building 600ft away?

Did you also ground the shield?

Let's find out what the problem is first. POTS travels for miles on twisted pairs without problems. I assume you are connected directly to the POTS terminals of a cable modem or similar and not a copper POTS line from the phone company? My thinking is that the line is not properly balanced to which you are connected. Wouldn't surprise me with a cable modem.

-Hal

That's a good point to mention, Hal. It is true that output ports on IADs, VoIP ATAs, EMTAs and other telephony toys are often used to emulate a real POTS line, but they often don't work.

I had an installation that called for the reuse of a pair in an existing 300 pair aerial cable to send a POTS line from an EMTA. This pair had carried a digital station on a Nortel system to a regular jack. It didn't take long to determine that Spectrum Cable's Arris EMTA lacked the horsepower to push clean dial tone that far. We obtained Viking Electronics' TBB-1B, which is a great per-line device that was developed specifically for these situations. Of course, you will need one per line.

HERE IS THE LINK FOR IT.

Well done, Ed!

Sam