ECN Forum Forums General Topics of the Trade Voice - Data - Video Discussion 2-way interference

Was back to this job today, it is a CB, using CH 26, and the dispatcher said he had someone check the radio all out for "RF leakage", said it was OK. Also, he said that sometimes when someone is on line 1 and a call comes in on line 2 it cuts off line 1. Guess there's a little more going on than they first thought. These ARE corded sets for multi-lines and I would need Sherlock Holmes to get the right info out of these guys, esp. when they are busy. They aren't too concerned about the problem and I am real busy, so I am not going to see it resolved I guess.

Sorry this little "brain teaser" from real life wasn't more fun, thanks for the input.

The best bet is to try separation of the phone wires if they are near the antenna/feedline. Next would be curative measures at the phone end. The ham radio magazine "QST" has ads for telephone filters and phones that are bullet proofed. The magazine can probably be obtained at your local library or just do an internet search. I don't know if the filters are designed for commercial type phones or just residential. In either case, most of the folks selling these devices used to work in the telco/communications industry and might be able to give you some detailed information specific to your problem.

It's a sad thing that there are no mandatory RF immunity standards in this country; we are the only industrialized country in the world without any. I used to hear this type of complaint just about everyday and the complainants don't want to hear they have to cure the problem. I worked for the FCC for 30+ years in the Saint Paul MN field office, so I am quite familiar with the issues.

poorboy,
Is there some sort of a phone-patch on this between the phone and the CB transciever?

There shouldn't be.. phone patches are not permitted in the CB service.

Check to make sure that they have a good ground for the antenna/tranceiver. Also make sure that they are not using any amplifiers with the radio, as the ones that are available for CB are generally of poor construction, and are highly illegal to possess or use.
http://www.kyes.com/antenna/interference/tvibook.html http://www.sncmfg.com/telecom/noise_protection/rid.html

techie,
I've got a heap of CB manuals here that state how to (in the US) hook up a CB transciever to a phone patch.
What's your take InspectorE?.

Right from the horses mouth...

Title 47: Telecommunication
PART 95—PERSONAL RADIO SERVICES
Subpart D—Citizens Band (CB) Radio Service
How To Operate a CB Station


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§ 95.420 (CB Rule 20) May I connect my CB station transmitter to a telephone?
(a) You may connect your CB station transmitter to a telephone if you comply with all of the following:

(1) You or someone else must be present at your CB station and must—

(i) Manually make the connection (the connection must not be made by remote control);

(ii) Supervise the operation of the transmitter during the connection;

(iii) Listen to each communication during the connection; and

(iv) Stop all communications if there are operations in violation of these rules.

(2) Each communication during the telephone connection must comply with all of these rules.

(3) You must obey any restriction that the telephone company places on the connection of a CB transmitter to a telephone.

(b) The CB transmitter you connect to a telephone must not be shared with any other CB station.

(c) If you connect your CB transmitter to a telephone, you must use a phone patch device with has been registered with the FCC.
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This is the "plain english" cb rules that were adopted quite some time ago. The upshot of telephone interconnect in cb is that one of your own transmitters has to be at the connection point. If a cb station is going to connect five different users, each of the five would have to provide a transceiver. The lawyers essentially wrote the rules this way to prevent someone from becoming a telephone system. It would have cut into the $$$ that the regular telephone companies were making with the old style mobile telephones. You've got to remember, this was long before cellular telephones. Some folks carried pagers, but not that many. And, ships at sea still used manual morse code to communicate.

You're right.. I was thinking of automatic patches.. I may also have been thinking of FRS and MURS, for which connections to the PSTN are not allowed.. [ 95.193(e), 95.1313 ]