FM RADIO NOISE FROM PSTN LINES

[070973eco]

Hi,

Actually a customer has a troubleshooting with his UC-560, this device has a VIC2-4FXO card receiving 4 lines from the PSTN, the Inbound calls from the PSTN have a FM Radio Noise, we can hear multiple stations radios when the call is answer. What´s going on? The UC560 is correctly grounded, we installed filters to ADSL service, etc. and nothing fix this problem. The PSTN provider says that the UC560 or the FXO Card are the noise suppliers, this is incredible for us. What we should do?

Thanks in Advance.

[greenturtlesteak]

Hi Edgar,

Have you tried disconnecting the lines from your UC560 and hooking a buttset up to the block to see if you still hear the same noise on the lines? Sounds like an issue with the line itself, but you'll have a hard time getting your carrier to own up to it unless you take the UC560 completely out of the picture. Give that a shot and let us know how it goes.

Cole

[paolo bevilacqua]

you'll have a hard time getting your carrier to own up to it unless you take the UC560 completely out of the picture.

Rated!

[hoorock89]

I'd even recommend adding and testing a generic SIP trunk on the box just to prove that voice services from another source will arrive without the same interference.  Make some test calls across those trunks and prove that the interference isn't coming from the UC500 itself.

[rcastill]

If you are looking to do some testing with a SIP trunk provider to make sure this is just a POTS line issue you might try www.les.net  I believe they offer a free SIP trunk that you will be able to use for testing after you listen to the add they run everytime.  As a second option you can consider www.didx.net; they will send you credentials to test a SIP trunk on their service for 30 days.

All the best,

Robcast

[rcastill]

Radio on POTS Lines
Normal radio troubles on the Plain Old Telephone Service (POTS) are interactive: they require that an entity act as an antenna, and that another entity act as a receiver tuned however well or poorly -- to the frequency offered by the antenna. Outside plant (OSP) and inside wire can act as an AM antenna, and the customer’s telephone becomes a crude radio.

When OSP is properly engineered and constructed, it is bonded and grounded so that the entire loop is shielded from noise. A properly shielded and grounded underground drop will carry that protection to the network interface ground, but unshielded aerial drop can often act as an antenna.

Most POTS radio interference can be corrected simply by grounding out or eliminating the antenna. If a buried service drop is the culprit, make sure that the drop is grounded and bonded at the terminal and at the Network Interface. If aerial drop is suspected, replace the drop with a 2-pair drop with a metal messenger grounded at the terminal or Category 5 drop.

Try a 66 block with a lightning arrestor to see if you can "ground out" the problem.  I have added a link.

http://www.telephonecentral.com/Products/25-Pair-Lightning-Protector__110422.aspx

All the best,

Robcast

[David Trad]

Hi Robert,

Good post and highly rated

Was going to also suggest if they cannot ground the line in the event that their local laws may not allow them to, then potentially another way to mitigate it would be to use a fly lead that has an isolation unit around it, and or run it through a central splitter that has some form of grounding right at the boundary point.

This has worked in the past to varied degrees, it is not a sure fire way of doing it, but it can bypass laws in certain locations that may prevent you from doing as you suggested

Cheers,

David.