Yet another strange question from yours truly: on the roof of my house,
anchored to the chimney, is a large outdoor antenna. No idea which
antenna - it was installed before my time, probably 15 years ago (or
more) and, for various reasons, I can't climb on the roof to find
out. From that antenna and into the house runs a brown cable (or is it
wire?) labeled "Belden Celluline 9275 300 ohm UHF transmission" and
a bunch of patent numbers.
For some strange reason (it may have been done by the cable company
when cable was first installed in the house - also before my time),
that Belden cable was cleanly cut mid-way through its run across the
basement. While it doesn't look like any twin-lead cable I've seen
before (and, admittedly, I haven't seen that many), it has a white
core which looks like frozen foam and what appear to be two very thin
metal lines, one on each side of the core.
And the question: I want to find out if that antenna+cable setup still
delivers a signal. I would like to do it by connecting the Belden
cable to a standard RG6 coax and then to a regular or HD tuner. I
understand that this connection would require a gizmo called a balun
but that's as far as my understanding goes. So what type of balun is
it (if there is more than one)? How difficult is it to find? I imagine
I need to strip the Belden cable on one hand and the RG6 on the other
in order to connect them to the balun. Is it possible and, if so, how
is it done?
Typically a 300 to 75 ohm balun will have a pair of screw terminals for
the twin lead connection and an F connector for the coax connection.
Thus the twin lead simply needs stripping and screwing (yes, I know how
it sounds) but the other side will require that you install the
appropriate connector on the coax to match to the connector on the
balun. Sadly the most common sort of balun to be found has a male F
connector and the most common F connector for coax is also a male so you
will probably have to come up with a female-female F adapter to match
You can pick up a 300 ohm to 75 ohm matching transformer from Radio
Shack, Wal-Mart or even Walgreens for a couple of bucks. The 2 wires
from your existing flat cable connect to one side and a coax cable
connects to the other through a standard F connector.
300 Ohm foam Filled Transmission Line, Matching Balum 300 ohm to 75 Ohm with
the appropiate terminals will work just fine with minimual loss. The
Matching Devices can be probably bought at the local Radio Shack or any
Radio TV Supply.
TN climate may have rusted out your 300 ohm rooftop antenna, making
your old system low quality or possibly useful to a radio.
see hdtv antenna compass directions from entering just your zipcode at:
That old twin-lead cable reminds me of the setup in our city apartment
building back in 1961. The twin-lead was connected directly to the
back of the TV with screw terminals. Occasionally a wire would break
and it would be necessary to re-attach it. The problem was how to
strip it... The plastic dielectric was the most awful, stiff material
Thankfully my father showed me the way. He lit it with a match and
burned away the plastic from the bare copper wires. I still remember
the drip drip of hot plastic and the nasty smell it produced.
There weren't many stations, just the ABC, CBS, NBC and a struggling
PBS affiliate that ran shows about "math lessons" for educational TV.
There was also one big-city independent station that ran Laurel &
Hardy, Abbott & Costello, the 3 stooges and some fine local children's
Every few months a tube on the set would go bad. Then we called the
Zenith Repairman who brought no less than 3 giant tube caddies and
filled up the living room with spare replacement tubes when the cases
were open. Later, every drugstore had a tube-tester available and we
could test and sometimes even replace our own tubes.
On Tue, 24 Jan 2006 05:01:30 GMT, not firstname.lastname@example.org (Beachcomber)
It really pisses me off that you cant find tube testers in drug stores
any longer. Whatever happened to "SERVICE". I finally had to buy my
own tube tester and now I have to test them alone in my own home. The
drugstore tube tester used to be a great place to pick up women,
particularly those who had broken tvs. It's no wonder there is so
much violence in today's society. People no longer have a place to
gather and test tubes. It was always a big thrill to watch them light
up, and slowly watch that meter climb into the "GOOD" (green)
zone. That was so much more exciting than all these boring computer
games these kids play these days.
By the way, 300 ohm tv cable will still work if it's still properly
attached to the antenna and the antenna is still intact. To splice
it, strip it back about an inch on each piece. Twist the two wires
and bend them down along side the cable. Wrap with tape. Connect to
tv and see what happens. On newer tvs you will need an adaptor. A
couple bucks at Radio Shack.
On 23 Jan 2006 18:09:50 -0800, email@example.com wrote:
There you go, 300 ohms. Just like other flat lead.
This white foam might be easier to strip than the flat plastic.
You could use screws and nuts to attach this current antenna to the
flat lead side of impedance matching transformer, the small white or
black cylinder 1 3/4inches by a half inch, with flat lead coming out
of one end, and the coax connector at the other end. (Between a
dollar and 2.25. Though only surplus and hamfests charge a dollar.)
And later you could solder the leads if you wanted to.
The female coax connector on transformer will fit well with the male
one on the piece of coax cable you will buy or make.
Some bigger wider ones have screw terminals for the flatlead, and if
the washer has teeth, supposedly you don't even have to strip the
wire. And they may have coax wire coming out with a male connector.
That's when you'll need a M-M adapter, only about 2 or 3 dollars They
sell bothl M-M and F-F adaptors.
www.mouser.com has everything.
I haven't done it, but I think you can just connect the flat lead to
the coax input of a tv, and you'll still get a picture, even if it is
not the best quality. Stick one wire in the hole and touch the other
lead to the threads. Still, I guess if there were no picture, I'd
still try it with the matching transformer.
I used an outdoor antenna in Indianapolis in the 60's and NYC in the
70's and 80's, with flatlead. I didnt' do anything about lightening
protection in either place, and never had a problem. But maybe I
wouldn't do these hookups during a lightening storm. Don't know
whether that caution is necessary or not.
In Brooklyn, I was up on the roof of the apartment building and found
an antenna above my apartment. No one else seemed to be connected to
it, and the wire ran right by my window, so I just connected myself
for 10 years of ghost free viewing.
Remove NOPSAM to email me. Please let
me know if you have posted also.
If the signal is strong enough. Some places you can even get something
with no antenna connected.
During the late seventies, I was living in an apartment building that
had an antenna with a distribution amplifier (a big one using tubes)
with a connection to each apartment. That amp was still working even
though no one was using it.
Thanks everyone for the info. One piece is still missing (at least for
me) - how do you actually strip a clean cut twin-lead wire?
Beachcomber's retelling of his father's method - burn everything around
the wires - sounds good, except that if I do that in the basement
(where the wire terminates and air circulation is minimal) - the
resulting smell will probably be grounds for divorce and a major
violation of zoning regulations :)
Nevertheless, I'm willing to use that method as a last resort. Question
- is it actually the last resort?
Not only smell, but lots of smoke :)
Back in the good old days (around the time sunshine was
invented) I would have done it in your house by putting
the lead flat on top of something hard and not important...
the top of my caddy, perhaps). Then with a knife I'd cut
a slit clean through it alongside each of the wires for an
inch or so. Next fold back the resulting center piece and
cut it off. Now you're left with what for all practical
purposes is just two separate wires, easily strippable with
side cutters or your knife.
I hope that's well enough explained. :)
Some matching transformers don't require the 300 ohm wire to be stripped at
all. I don't know if they're still available, but basically, the flat cable
went between two screws. The screws had a "star washer that was shaped like
an inverted bowl. When the screws are tightened, the sharp part of the star
washer would pierce the insulation on the cable and provide a connection to
the inner wires.
Since you have the foam filled stuff it's a little more difficult to
trim away the center so I'd use a utility knife to make a slit along
each side and pull the wires out. Then just cut away the remaining
center carcass. Finally, attach the leads to the wire leads or screw
terminals of the matching transformer.
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