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post #1 of 25 Old 12-05-2010, 04:04 PM - Thread Starter
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Hello,
I was hoping someone could help me with a source for an adapter to the antenna connection in my apartment building. My building has a rooftop antenna. It is an old style plug and I've been searching all over the internet, been to radio shack/hardware stores to see if anyone can help me. Haven't been able to find anything yet.
The connection is a female wall plate that would receive a 3 prong adapter. I have attached a photo of the plate, and back of the plate. I need to find the male end which would be a 3 prong connector.
Any ideas where I can buy an adapter?
Or, any ideas on for a new wall plate that would work with the existing wires in the wall?
LL
LL
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post #2 of 25 Old 12-05-2010, 05:12 PM
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What your building has is an old-fashioned distribution system that terminates in 300 ohm twin-lead connections. Don't even think of replacing the plate. You are likely to screw up more than just your own connection. You need to find the corresponding plug and connect it to a 300-75 ohm balun to use with modern gear.
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post #3 of 25 Old 12-05-2010, 10:54 PM - Thread Starter
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Colm,
Thank you for your follow up and recommendations. Would you happen to know a source of where I can find the plug that works with my current connection?
I'm not very familiar with what a 300-75 ohm balun is. Could you help elaborate on what this will do for me? Also, where can I purchase one of these?
Thank you for your help,
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post #4 of 25 Old 12-06-2010, 06:22 AM
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Quote:
Originally Posted by EdzBenz View Post

Would you happen to know a source of where I can find the plug that works with my current connection?

Never seen that type before - did you try asking the apartment maintenance folks? They may have them or at least know what it's called or where to find one...

Quote:


I'm not very familiar with what a 300-75 ohm balun is. Could you help elaborate on what this will do for me? Also, where can I purchase one of these?
Thank you for your help,

http://www.summitsource.com/product_...ducts_id=10240

I think most of us probably have a half dozen or more of them laying around from previous decades...

Jeff

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post #5 of 25 Old 12-06-2010, 07:44 AM - Thread Starter
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Jautor,
Thank you for the website link. I guess I didn't know the technical name for a balun. I think I've got one of those laying around somewhere.
The folks in my apartment building have no clue where I can purchase a plug for the connection. The building just had its antenna upgraded and fixed, so I'll probably have to call the company that did the work and have them take a look see.
Still open to more suggestions, but it sounds like I'm running out of options on a DIY for this job.
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post #6 of 25 Old 12-06-2010, 03:58 PM
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The best solution would be to replace the old tap in the wall with a new one with a 75 ohm F-connector so you could just connect coax to it. It would have to be done by someone who knows what they are doing, though.

A workable kludge might be to strip the insulation off the end of the twin lead on the balun, bend each wire over three or four times, twist each wire so that you have something thick enough to make contact in the socket, stick one wire in the left hole and one in the right. You would probably have to tape it in position.
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post #7 of 25 Old 12-06-2010, 05:21 PM
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Quote:
Originally Posted by EdzBenz View Post
The folks in my apartment building have no clue where I can purchase a plug for the connection. The building just had its antenna upgraded and fixed, so I'll probably have to call the company that did the work and have them take a look see.
Upgraded and fixed? Do other folks have the same connectors, and do they use them? You should definitely call the company that did the work - if they can't tell you how to connect to it, your building shouldn't be paying them...

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post #8 of 25 Old 12-06-2010, 10:24 PM - Thread Starter
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Quote:
Originally Posted by jautor View Post
Upgraded and fixed? Do other folks have the same connectors, and do they use them? You should definitely call the company that did the work - if they can't tell you how to connect to it, your building shouldn't be paying them...
Good point, but they only fixed the broken antenna on the roof. Nothing with the wiring or connections within the building. The other residents have the mystery plug I'm looking for and are using it to get digital signals. They tell me that it works quite well. I'll probably have those guys install the 75 ohm F-connector in place of what I currently have per Colm's recommendation.

I really appreciate the help and information. I don't think anyone is going to be interested in learning about an update to this predicament (I do this on my mercedes forum a lot) because its such an old connection. But, I'll post what transpires for the sake of information gathering here.
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post #9 of 25 Old 12-07-2010, 09:22 AM
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Quote:
Originally Posted by EdzBenz View Post

The other residents have the mystery plug I'm looking for and are using it to get digital signals. They tell me that it works quite well.

If others have the plug, a picture of it might help, also check it physically on the chance that it has a manufacturer's name or other markings that may allow Google to help you...

Jeff

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post #10 of 25 Old 12-07-2010, 10:10 AM - Thread Starter
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Quote:
Originally Posted by jautor View Post

If others have the plug, a picture of it might help, also check it physically on the chance that it has a manufacturer's name or other markings that may allow Google to help you...

Jeff

Great idea. Didn't think of that one. Thank you,
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post #11 of 25 Old 01-03-2011, 01:53 PM
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Quote:
Originally Posted by Colm View Post

What your building has is an old-fashioned distribution system that terminates in 300 ohm twin-lead connections. Don't even think of replacing the plate. You are likely to screw up more than just your own connection. You need to find the corresponding plug and connect it to a 300-75 ohm balun to use with modern gear.

I am a neighbor of Ed's.

Colm, any idea where a corresponding 3-prong plug might be found?
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post #12 of 25 Old 01-03-2011, 02:25 PM
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Sorry, no idea. It is obsolete. IIWY I would put pressure on the building management to change out the taps for ones with F connectors.
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post #13 of 25 Old 01-03-2011, 08:13 PM
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Can you get a better, clearer picture of that jack apparatus? It might be simply some type of old-school T-tap that could be replaced by a modern F-connector tap or two-way splitter.

Just because there is a knob doesn't mean you should turn it.
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post #14 of 25 Old 01-05-2011, 02:11 PM
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This is the three prong jack
.

Additionally, there are painted-over jacks in the bedrooms which might be for TV. Are these TV?


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post #15 of 25 Old 01-05-2011, 03:24 PM
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Could you maybe get close enough to them so we can actually see the jacks? Does it say "TV FM" on the 3-prong jack? Also, most helpful would be to take a clear, close up image of the back of the plate, with the cables still attached, after you've unscrewed it from the wall...

Jeff

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post #16 of 25 Old 01-07-2011, 11:05 AM
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Quote:
Originally Posted by jautor View Post
clear, close up image of the back of the plate, with the cables still attached, after you've unscrewed it from the wall...

Jeff
^^^

I wasn't very clear. This is what I meant by better pictures.

Like the right hand pic in post #1, except clear and perhaps with the cover plate removed if possible, to really see the guts and what might be going on. A few different angles...as long as we're asking.

Just because there is a knob doesn't mean you should turn it.
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post #17 of 25 Old 01-12-2011, 06:26 PM
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Quote:
Originally Posted by whoaru99 View Post

^^^

I wasn't very clear. This is what I meant by better pictures.

Like the right hand pic in post #1, except clear and perhaps with the cover plate removed if possible, to really see the guts and what might be going on. A few different angles...as long as we're asking.




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post #18 of 25 Old 01-12-2011, 09:00 PM
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That type MATV distribution system was common from the 60's up to the 80's or so, especially in high rise apartment buildings and condos. They have been mostly surplanted by new 75 ohm coax cable TV and/orsatellite overwiring. So first of all, ask your neighbors or the building management if it's still in service! I'd be surprised if is, but if in fact it's still working, you can use it for OTA DTV reception. With the shift to the UHF band for most DTV transmitters, you may not get all the channels you'd like, however. If the building management has properly maintained the old system, it should have added the UHF antenna(s) on the roof as required for your market's new channel allocations a few years ago.

In those days most TV's only had balanced 300 ohm inputs to the tuner, so the wall plate side was usually a 300 ohm output (only the outer two pins were active, if I remember correctly), even though the in-wall wiring was 75 ohm unbalanced (coax). Jerrold (and others) made the mating plug; its size and spacing were an industry "standard" at the time. I remember my first apartment after college (dating myself, in the 60's) the building super had a box of the plugs and would give them to tenants on request, or you could just buy them at RS. Now they are scarce! (Do you have a building super or other management office that may still have some??)

Anyway, either by jury-rigging or using the correct plug, you can connect the old wall outlet to your TV using a 300-75 ohm balun and check it out. OBTW the other outlets in your photos are also 300 ohm TV/FM outlets, so it might be easier to try one of them first.

If one or more of them do work, it might be neater and better to replace the old wall units with something more modern, with a 75 ohm F-style connector. The problem is, it's not likely to be a splitter inside the box, but a directional tap or coupler. The old wiring style was not "star" split to each outlet, but rather "daisy chained" from the top floor to the bottom, usually at very high level, say +20 to +60 dBm, to overcome ingress. (that's why you see two coaxes on the back, one in from the previous jack upstream, and the other out to the next jack down the line). The directional tap output to the room was anywhere from say -10 to maybe -30 dB lower. So you'd need to find out the "tap" number, which hopefully will be stamped on the back. Look for labels like "in", and "thru" or "out" by the two coax connectors, and then a number like "-12 tap" close to the wires going to the 300 ohm output. If you see such a number, the whole thing can be directly replaced by a directional tap for $2-3 (from Blonder Tongue, Channel Plus, Pico, or dozens of other
makers) with a 75 ohm F output with a similar tap level number. Some are laid out with the output F-connector at right angles so it can be mounted directly on the back of a standard single-gang wall plate.

Some examples at: http://www.blondertongue.com/shop-by...s/indoor-taps/

Mike
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post #19 of 25 Old 01-13-2011, 03:56 PM - Thread Starter
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Mike,
Thank you very much for your extensive follow up. I'm going to digest this info, do some research, and see what I can do about swapping out the connector. Thanks again for your thorough follow up.
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post #20 of 25 Old 01-14-2011, 09:29 PM
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Balun is attached to screws tightened into wall jack.







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post #21 of 25 Old 01-14-2011, 09:46 PM
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Good kludge...
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post #22 of 25 Old 10-29-2013, 08:43 AM
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thanks a lot Mike, very detalied and easy to follow explanations.

 

i think i have a similar installation, old wall plate with 2 coax. However, mine has a single

hole in the plate, going into a metal sleeve about an RCA pin in size. From that sleeve, there is a wire going into a resistor? balun? then connected to the 2 coax cables

 

To connect to my room antenna cable, i have a piece of coax, with one end stripped. The bare copper pin is inserted that into the wall sleeve and bent around a little.

 

it used to work fine , then i had my floor done and they screwed up something. Previously i was getting 37 digital channels, now i'm getting only 24, no matter how i jiggle that wire.

 

Would you know what type of connector i would need and how to find it?

 

Many thanks and best regards!

 

Ion

 

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post #23 of 25 Old 11-12-2013, 06:03 PM
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I believe this is the plug you're looking for.

 

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post #24 of 25 Old 11-12-2013, 06:35 PM
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The back of that wall plate looks like the connector that was on am/fm receivers from the 60's and 70's for the FM Antenna. That so called balun may be for some kind of impedance matching. Could 1 coax be for UHF and the other for VHF? If that would be the case, you may just be able to discard that wallplate and get one with 2 F Female connectors on it and use the VHF for your FM Radio and the UHF for HDTV.

But what Satori84 says is correct, forget what I just said. It could be daisy chained.

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post #25 of 25 Old 11-12-2013, 10:57 PM
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Looks like a Motorola jack to me from the back and description. Hard to tell from the front picture. There were taps made with Motorola jacks. If that is what you have, you can get a plug at Radio Shack or a lot of other places. You can replace the tap with a new one if you can figure out the value. Or you can drill out the rivets holding the connector in place and replace it with an F-connector.
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