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Want to replace old flat tv cable with better coax.

I have done some reading about balun transformers and how I can connect my existing flat antena cable to 75 ohm cable.

However, my questions is this... what if I replace the 30 year old flat cable all the way to the antenna. Will this yield better reception? (It is pretty good as it is.) The exiting flat cable is starting to fall apart at some places. Currently I just have it directly wired to my coax cable (just before it enters the house) with out any type of transformer. The coax is properly grounded (to the circuit breaker box.)

So my questions are these:

  1. How do I connect the coax directly to the antenna? Or should I? Do I still need a balun transformer?
  2. If I need a balun transformer, does anyone know of a heavy duty outdoor one? (Or should I build my own.)
  3. Will reception improve?

Thanx to all who reply.

jg

Reply to
jg
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Yes, your reception will improve. You have a mismatched impedience now. Yes, you need a balun transformer. Around $5 at any hardware store, or Radio Shack. If the old cable is deteriorating, it's time to replace it. The balun comes with about 4 inches of flat cable that goes to the 2 antenna nuts, then the coax screws to it and goes to the tv stuff in the house.

Just do it. It's no big deal to do as long as you can get on the roof and to the antenna. Total cost is the balun, some electrical tape, and whatever coax you need. Then tape the coax to the mast with electrical tape. You dont need standoffs for coax.

(Be sure to wire brush the rust off the antenna nuts and coat them with automotive grease.

Mark

Reply to
maradcliff

When moisture gets into flat cable (300-ohm twinlead) it degrades the signal. If the insulation is cracked and the wires are exposed, it should be replaced all the way to the antenna. Don't use cheap twinlead. The good kind has foam insulaton under the plastic outer insulation. Connect the new twinlead just like the old one at the antenna. Clean the antenna terminals with some electrical cleaner spray and a plastic scrub pad. It might be better to replace the terminal screws, nuts and washers with new ones made of brass or stainless steel. This may require cutting and/or drilling the old screws off. They usually get corroded on an old antenna.

Currently I just have it directly wired to

If you decide to continue using twinlead to the antenna, you should install an impedance matching transformer where the twinlead connects to the existing coax. (See next paragraph below.) Twinlead has less signal loss than coax so it's preferred in reception areas where signal strengths are low. This may not apply in your case. Coax has greater signal loss than twinlead but better immunity to noise reception from home appliances. This is a consideration when deciding which kind of antenna lead wire to use. If coax is used all the way from the antenna to the TV it might require an antenna amplifier to make up for the signal loss in the coax. The amplifier is installed on the antenna mast. The power supply for the amp' is located near the TV.

If you want to connect 75-ohm coax to a TV antenna which only has two screw terminals for twinlead, you'll need an impedance matching transformer. This is the kind which is used on the back of older TV's that have antenna screw terminals instead of a female coax connector. The matching transformer has a coax connector on one end and two wires (pigtails) on the other. The pigtails would be attached to the two terminals on the antenna and the coax goes to the female connector on the matching transformer. You should use a transformer made for outdoor use. You can buy one at Radio Shack or home improvement stores that have a TV hardware department. The labeling will say that it's made for connecting coax to a TV antenna which has screw terminals.

Matching transformers for TV use are not expensive, so it's not worth the effort to make one. It's also not easy to make one that works well at TV frequencies, especially UHF. Proper impedance matching between antenna and lead wire is important for getting the best signal quality to the TV.

Reply to
HFguy

Thanx, I'll try it this weekend. I have some high end coax cable ready for the job. Only one more question... should I worry about the quality of the balun transformer? The ones I have seen at Home Depot/Lowes/Radio Shack look pretty flimsy. I know there is probably nothing inside that should not get wet, but I still wonder...

jg

Reply to
jg

I'm not sure what to tell you about the quality of them. I'd guess they are all made by the same company anyhow, but who knows? Use the boot that comes with them, and I tend to wrap electrical tape around that to be sure it stays dry at the coax connector. If water gets inside the balun, it's cracked and bad from the start. They are sealed. As another posted said, replace the screws and nuts on the antenna with brass ones if they are real rusted or corroded.

Mark

Reply to
maradcliff

The outdoor TV antenna baluns are sealed better to prevent moisture from getting inside and degrading the components. They also have a rubber boot to cover the coax connector.

Here are two URL's for Radio Shack TV antenna baluns. The second one has gold plated connectors which should make it more reliable for outside use.

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Reply to
HFguy

Should I be worried about this? Currently the twinlead only runs from the top of the antenna to where it enters my house. About 40 ft. Then I have coax in my crawl space for another 80 feet or so. 30 ft of which is just coiled and wasted. Reception for local (Sacramento) stations is pretty good. Reception for San Francisco stations is too grainy to watch at times. My zip code is 95682. (So I should not expect too much from San Francisco.)

If need be I can replace the existing twinlead with new twinlead. Should I look into this?

jg

Reply to
jg

While you are at it, you may wish to replace the antenna as well. If you do be sure to get one with good UHF reception. Once the US switches to digital TV, I believe in 2009, all TV signals will be in the UHF band.

Reply to
Jeff

That's not true. VHF High Band and UHF.

Reply to
David

JG,

I agree with everyone here that coax is better but so far noone has mentioned there are two types of coax, 50 ohm and 75 ohm. Make sure that you use the 75 ohm coax. 50 ohm is generally used for communications and you can't tell the difference between the two by the size or thickness of the coax. You can tell by the number stamped on the coax, eg. RG75U, etc.

J

jg wrote:

Reply to
Joey

If you want the best weak signal reception (San Francisco) either use new twinlead all the way from the antenna to the TV or new coax all the way with an antenna amplifier too. You might want to consider an antenna rotator if the local and distant stations are in different directions. BTW- If you use twinlead, install it with a continuous twist along it's length. Make several twists per yard. I know it's a pain to do this but it helps to reduce the reception of noise from home applicances on the twinlead.

Reply to
HFguy

Maybe. :)

How did you do that? Soldered one wire to the center and the other to the braid? I'm curious, but as others have said, you should redo it, and run straightaway to a tv or a signal splitter, if you want to go to more than one tv. They still sell them for flat lead.

I would also pay attention to the way the wire is run now. Flat lead should have stand-offs to keep it away from the pole and the siding, and as someone pointed out, it should be twisted I can imagine that some prior amateur or neat-freak kept the wire untwisted because he thought it looked better. So if they didn't do a good job the last time, your job can be better. (The interference will still try to interfere, but its effect on one part of the flat-lead will be exactly the opposit of its effect on the other part of the wire, so the two effects will cancel each other out. Hence, no interference. This is similar to the reason that wires from burglar alarm sensors use twisted pairs of wires, so that lightening won't generate a voltage spike in the wires that will damage the control panel (or set off the alarm?).

Yes.

They're not so much heavy duty as they are designed to keep the insides dry, with the rubber cover and all.

Remove NOPSAM to email me. Please let me know if you have posted also.

Reply to
mm

You haven't told us what type of tv antenna you have, and whether or not you have a rotor. To get San Francisco stations in your area, you must use a rotor as the Sacramento stations and the San Francisco stations are not coming from the same direction. Also, to get the UHF stations from San Francisco, I recommend the Channel Master 8-bay bowtie. It is very common in Sacramento to have separate VHF and UHF antennas as it is fairly easy to get decent reception from San Francisco, Santa Rosa, Concord, Chico, Redding, Reno, and even more, as well as all the local stations. But you MUST have a high-gain antenna with a narrow beamwidth. Otherwise, the local stations will interfere with the distant stations. As in Fresno (where I now live), with a high-gain antenna with a narrow beamwidth, it is possible to get more than one station on the SAME channel, just by turning the antenna. I recommend NOT using any pre-amp at the antenna as the powerful Sacramento stations will wipe out most of the distant stations. Generally speaking, in the Sacramento area good coax cable will work better than twin lead, especially if you are around any electrical interference. Also, even twisted twin line can pick up signals that may interfere with the distant signals. But DON'T have several feet of coax wound up in your attic. Every foot of lead, whether twin lead or coax, adds to signal loss. Generally speaking, the antenna should be mounted as high as possible, although this is not always the case, especially with UHF signals. There is never a guarantee as to what you will receive. As far as using a balum at the antenna (and at the tv if necessary), all balums are NOT created equal. Different samples from the same manufacturer can vary greatly in the amount of signal loss, etc., especially at the UHF frequencies. For the antenna AND balum, I recommend staying away from Radio Shack. In Sacramento, the most popular antennas for picking up San Francisco, are made by Winegard and Channel Master. The BEST UHF antenna you can use is the Channel Master

7-foot parabolic but strong winds can cause problems if the mast is not strong enough. I used the 7-foot parabolic on a 30-ft. mast with rotor and got excellent reception from most of the UHF stations from San Francisco. Second best is the 8-bay bowtie. For more information, read my article in RADIO ELECTRONICS magazine, August 1982, titled HOW TO SELECT THE BEST TV ANTENNA. You should be able to find that issue at a library.
Reply to
garyarnold

How did I connect the twinlead to the coax? I used two cones and twisted them. Center to one lead, outside to the other lead. This was meant to be a temporary solution (two years ago.)

At any rate I have one more question, if I go twinlead all the way from the antenna to the TV (almost to the TV, I'll have to switch over just before cable runs up the wall behind my tv) should I be concerned with grounding? As I explained before, coax is well grounded just before entering crawlspace. Will I need to do the same for twinlead?

Reply to
jg

You can't expect good reception by mixing the two kinds of cable. Use one or the other. Coax is preferred. You get less ghosts with coax, and most likely better signal. Depending on your directions, an antenna rotor may benefit you. That way you can point it toward SanFrancisco or your local towers.

BTW: Coax is easier to install. You dont need all those standoffs and stuff.

Reply to
maradcliff

Yes, this is correct. Most hardware stores only carry the 75 ohm RG75U these days. The 50 ohm was popular in the 70's and 80's during the CB radio craze, but is seldom used these days except by amateur radio people and the few that still use CB. In fact Radio Shack no longer carries the 50 ohm cable in bulk. I wanted a piece for my scanner and they only had pre-made cables, and not the lengths even close to what I needed. I finally chopped a piece off an old CB antenna and soldered on my own ends.

Geeezzzz, I'm having a brain fart.... Is that RG50U.... ???? Don't sound right.... The older I get the more my memory fades !!!

Reply to
maradcliff

Cones?

Wirenuts?

Are you in the USA?

LOL

My mother paid a tv guy to connect our tvs to the rooftop antenna, back in 1957. When I was in the attic several years later, a little before she was going to move, I saw that he had just twisted the wires together, even though there was a flatlead antennal splitter hanging right there, not being used.

The purpose of grounding iirc is for lightening protection. Lightening protection is NOT accomplished by providing a path for the lightening to reach the earth. A conductor would have to be enormous to accomplish that (as big as your thigh?).. It's accomplished by providing a path for excessive charge in the antenna or any piece of high metal to dissipate to the earth, so that the lighening will not be attracted by that charge.

This question is beyond me.

Remove NOPSAM to email me. Please let me know if you have posted also.

Reply to
mm

I couldn't tell you what kind of antenna I have if my life depended on it. It is big and it is very high. At least 40 feet high. If memory serves correctly, I only have one antenna for both VHF and UHF. (Too dark to see right now.)

As for the direction, both the Sacramento and the San Francisco stations are in the same general direction. I am about 40 miles East of Sacramento and given that the Sac antennas are in the Delta by Stockton, I pick up San Fran stations as well. Ironically the station that I really want to pick up does not come in at all, it is Channel

  1. (I want my kids to watch Spanish cartoons and I refuse to pay for cable.) I think Channel 19 is East of Modesto some place. (I had a link to a site that pinpointed all towers on a map but I have since lost it. Maybe someone here knows of the site.)

So as of earlier reading I was leaning towards coax, then twinlead (to minimize loss) and now I'm confused all over again.

This is basically a summary of what I have gleaned from you gusy...

Coax: Pros:

--Easy to install.

--Less suseptible to interferance.

--I have a huge roll ready for deployment. Cons:

--More lossy

Twinlead: Pros:

--Less lossy Cons:

--More difficult to install.

--Must twist.

--Must purchase about 100 ft.

--Must purchase hardware to keep away from mast and wall.

Come the weekend, I'm doing one or the other... so I better decide by then.

Thanx again to all who replied.

jg

Reply to
jg

Your best off to use RG6, if using coax. Its lower loss than the more common RG59

You can avoid all these issues by getting satellite TV! In most areas of the country they carry lour locals.

all conveient on one pizza pan sized dish, and bets of all they have DVR, digital tv recorders built in.

you record what you want, to watch anytiome you care to, and can skip thru commercials. one version is called TIVO. a hour of prime time has

15 minutes of commercials, well thats now my time to do with as I wish!

satellite tv has free installs, with no commitments if you get the right package. you have nothing to lose!

Reply to
hallerb

RG-6/U is 75 Ohm. RG-58/U is still fairly common for ethernet.

Reply to
David

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