Author Topic: Telephone line causing radio interference?  (Read 1983 times)

Offline Mr. Bones

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Re: Telephone line causing radio interference?
« Reply #15 on: December 31, 2015, 09:36:45 PM »
And the filter carried through to the 300 series phones. This is for a 304C/5304C. Same filter.

Question is, does the filter prevent the radio from interfering with the phone or the phone from interfering with the radio?
I believe the winning answer, at least according to the Laws of Physics, and based upon experience, is RF can work either direction. Just depends on the circumstances. ;)

Lex III: Actioni contrariam semper et æqualem esse reactionem: sive corporum duorum actiones in se mutuo semper esse æquales et in partes contrarias dirigi.

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« Last Edit: December 31, 2015, 09:44:28 PM by Mr. Bones »
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Offline AE_Collector

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Re: Telephone line causing radio interference?
« Reply #16 on: December 31, 2015, 11:43:52 PM »
No idea about the radio but I bet he didn't replace any wire but rather cut you to another cable pair to the CO. The old one probably had a partial tip or ring cross to another cable pair which was killing the ringing voltage.

Terry

Offline Brinybay

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Re: Telephone line causing radio interference?
« Reply #17 on: January 01, 2016, 01:22:11 AM »
No idea about the radio but I bet he didn't replace any wire but rather cut you to another cable pair to the CO. The old one probably had a partial tip or ring cross to another cable pair which was killing the ringing voltage.

Terry

Replacing a wire is what a neighbor said he did. I didn't watch him, I was busy with other things at the time.
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Offline G-Man

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Re: Telephone line causing radio interference?
« Reply #18 on: January 01, 2016, 06:09:28 AM »
 Other than possible dial-clicks, it is very doubtful your telephone line adversely affects your radio reception. To the contrary, it is more likely that it would enhance it.
 
Back in the early days of radio, the telephone company had to admonish subscribers who were coupling their AM radios to telephone lines in order improve their reception.
 
61P filters were used to prevent dial clicks from being heard on adjacent AM radios. Other 61-series filters were similarly used for either DC buzzer/ bell noise from being picked up on radios that were close-by.
 
On the other end of the spectrum, radio interference that is picked-up on telephone lines is still a common occurrence.
 
Western Electric manufactured the 425J network for telephone sets to deal with subscribers hearing radio broadcast on their line. They also manufactured the 1542 and other special filters, for insertion in series with an incoming telephone line to suppress this type of interference.

Offline G-Man

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Re: Telephone line causing radio interference?
« Reply #19 on: January 01, 2016, 06:25:09 AM »
 There were several types of filters and methods to prevent r.f. interference to telephones and telephone -lines. I have already mentioned a few of them in my prior post.
 
Another that just came to mind, it the 129F condenser; commonly seen mounted across the transmitter terminals in handsets. Amongst other problems, radio interference caused the carbon granules inside of transmitters to “coher.”  Here is an extract from a Bell System Practice that addresses this problem:
 
TRANSMISSION ZONING OF STATION APPARATUS
 
 1.12 F1-type Handsets and some E-type hand sets are not equipped with an anti-packing condenser bridged across the transmitter as this is not required at anti-sidetone stations except in the case of radio interference from adjacent broadcasting stations. In this case a 129F condenser should be mounted under the transmitter contact springs of F type hand set or E type hand set equipped with a 625A
transmitter having 129F condenser. All F2 and F3 type handsets come equipped with this condenser.

1.13 Handsets if used at common battery side-tone stations must be equipped with a 129F condenser.

Offline AdamAnt316

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Re: Telephone line causing radio interference?
« Reply #20 on: January 02, 2016, 10:40:52 PM »
And the filter carried through to the 300 series phones. This is for a 304C/5304C. Same filter.

Question is, does the filter prevent the radio from interfering with the phone or the phone from interfering with the radio?

To the best of my knowledge, the idea behind a filter like that has more to do with the dial contacts than any other part of the phone. If I have one of my shortwave radios powered up and I attempt to dial a number using one of my 'un-filtered' 300 sets, I can hear the clicks of the dial pulses through the radio's speaker. My 211/G1 has the filter installed, and I'm pretty sure its dial pulses do not get picked up by my radios.

Speaking of radio interference and telephones, my grandparents had the opposite problem for many years. They lived within sight of the antenna tower for a 50KW AM radio station, and occasionally the signal would get picked up by their phone lines. On the worst days, you could pick up any phone in the house, and hear the station clear as day coming through the receiver almost as strongly as the dial tone! I believe the issue did get solved eventually (not sure exactly how, though the switch to DSL probably helped).
-Adam

Offline Brinybay

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Re: Telephone line causing radio interference?
« Reply #21 on: January 03, 2016, 12:05:56 AM »
Ok, mystery solved (somewhat).  You're correct if you said it was purely coincidental to the phone line fix.  It has something to do with the antenna connection.  The length of telephone station wire that I'm using for an antenna may have a break in it somewhere.  When I went to move it, the radio went silent.  I moved it again, it came back in loud and clear.  Then it went out again when I touched it, but I could hear it (barely) if I turned the volume all the way up.  At least I'm hoping it's just the station wire and not something else with the radio itself.

My apologies for starting a ruckus.
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Offline 19and41

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Re: Telephone line causing radio interference?
« Reply #22 on: January 07, 2016, 01:57:20 PM »
If any of your equipment uses wall transformer/power supplies, these are notoriously rich with RFI that can take out a substantial portion of your AM dial.  I just had to retire a simple LED night light that splattered the shortwave bandwidth of my console radio. 
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