Folded-Dipoles are amazing!
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Folded-Dipoles are amazing!


This is a discussion on Folded-Dipoles are amazing! within the DTV | HDTV Reception and Antenna Discussion forums, part of the Over-the-Air (Antenna TV) category.

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  1. #1
    DTVUSA Jr. Member
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    Folded-Dipoles are amazing!

    Considering where we live, we're probably lucky to have good reception, even though we're only 45 miles away in mountainous terrain.

    TV FOOL

    Like many folks here, I've been building antennas:

    First one was the popular coat hanger/cat whiskers. Only tested indoors, it didn't receive anything until I added a tin foil reflector. Then I got one flaky channel. Not much, but more than I expected. It was also huge and ugly.

    Second antenna was a small Yagi (I always thought it was Yagi. Now I'm seeing Yaqi?). PCB Antenna Specification Data
    Indoors, nothing. Outdoors, several channels from the top of a 5-foot step ladder.

    Then I built myself a 47-inch dipole. While I was looking for a vintage VHF amplifier I have, I stumbled onto a pair of Radio Shack telescoping whip antennas. From the top of the ladder and without the amplifier, the TV stored more than 20 channels. After enclosing the assembly in PVC, I mounted this to the remnants of a satellite dish mount. After adjusting the position and height, I got Channel 2.1 (RF: 27) through 50.1 (RF: 45) and everything in between (11 channels). My Samsung TV only tells me relative signal strength, but I recorded 5 to 7 bars, with VHF being the strongest. I'm still amazed at how broad the bandwidth is for such a simple thing, but it was a bugger to get aimed correctly. It may be broadband, but it must have a knife-edge for beam width. While I was reading and studying, and playing with calculators, I kept bumping in to folded-dipoles. That's when the bell rang and the light went on...

    Now focused on folded-dipoles, I've built three or four. The wire diameter isn't critical. I used 12 AWG solid aluminum electric fence wire, 26 AWG magnet solid wire, 14 AWG solid copper, and (my favorite) 18 AWG stranded hook-up wire, The wire-to-wire spacing isn't critical either. I built a couple on the outside of the PVC using it as a former. Then I started using a 7/8" dowel as a former so I could stuff it inside the PVC.

    I don't even remember now where I got the numbers or which calculator(s) I used, but the first was too long so I cut it in half. Then it was too short so I made another somewhere between the two. Then I started cutting it down in half-inch increments. Ultimately, I ended up with a 21.5-inch folded-dipole, totally enclosed in PVC, on top of a 6-inch pipe nipple, mounted to the dish mast with a couple of hose clamps. It still gets Channels 2.1 through 50.1 at 8 to 10 bars. Without an amplifier. It actually gets more than 30 channels, but I don't speak the language(s).

    Anyway, I'm posting this because I'm hoping to pique someone Else's curiosity about these and built one for themselves. I'd like to know if others get similar performance. It only takes about ten minutes to construct (if you're slow) and you can test it from the top of a short step ladder.

    VHF/UHF Folded-Dipole
    -----------------------------

    10 minutes to build
    < $2 in parts
    < 24L x 1.25W x 2H (without the pipe nipple)
    Very good signal without an amplifier
    Wide band and wide beam
    Folded-dipoles.jpg

    This is what's up today. Maybe I should put a little effort into wire management.
    Fin-dipole.jpg
    Last edited by sweller; 07-01-2013 at 12:11 PM. Reason: Fixed typos and added finished installation pic.

  2. #2
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    to the forum, sweller!

    Important to distinguish whether we're talking about channels or stations. Your TVFR tells me a decent outdoor VHF/UHF antenna should get you at least 23 stations (everything above 21 dB NM except possibly K49KF at 283 degrees magnetic) received reliably, not just stored in TV memory. That equates to approximately 57 channels! You're in a very good location.

    A lot of those stations are really retransmitters, so may duplicate other stations.

    I'm pretty sure the word you're looking for is "Yagi." Yagi-Uda antenna - Wikipedia, the free encyclopedia

    Amplifiers aren't normally recommended unless you're splitting to several TVs. The first thing the RF signal hits in your TV is an amplifier that nicely matches that tuner.

    If you want to try to get even more channels, you might want to build a Hoverman antenna! There are DIY plans all over the internet.

    The Gray-Hoverman Antenna For UHF Television Reception - Digital Home Canada
    Single Bay Gray-Hoverman (SBGH) Antenna : DIY TV Antennas

    Rick

  3. #3
    DTVUSA Jr. Member
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    Thread Starter

    Thanks for the kind reception, Rick.

    And thanks for clarifying the differences between channels and stations. I'm old. Once upon a while ago, there wasn't a difference. You're also correct that when the TV scans, what it stores isn't necessarily watchable.

    My experiments started with wanting to know what I could receive, and what I'd need to receive it. It's kind of funny because when we moved here, I was told there was no OTA reception. I now know that folks that live in Los Alamos proper (1000 feet higher up) have a less than 50% chance of getting reliable reception. My testing confirmed your point about a decent VHF/UHF antenna, but I still wanted to know how much VHF/UHF antenna, how high, do I need an amplifier, a mast, etc...

    I did consider a Gray-Hoverman and other types, but almost all of them are UHF. I needed a multiband antenna. And I have two more significant problems. Nothing can go in the attic due to a Pro-Panel (sheet metal) roof. The other obstacle is wind load. When I first mounted the dipole, I used PVC for the vertical. About as stable as a rubber band. I swapped it out with a long pipe nipple, solving part of the problem. But then the horizontals waved around like a scarecrow. I didn't write it down, but I remember that when I tried the dipole with an old VHF amplifier, I got more than 50 channels. But again, many were either not reliable or were not in my native language.

    There is *one more* thing I had to take into account. Spouse Acceptance Factor. As long as I can spend $0, and she can watch America's Got Talent, I'm golden.

    And so, being a firm believer in simplicity, I'm tickled with this tiny broadband folded-dipole. Especially when I think about how much I spent on inferior satellite service.

    Afterthoughts:
    The folded-dipole is much easier to aim than the dipole.

    In theory, a folded dipole has more gain (over isotropic - 5.64 vs 2.14) than a dipole. I do get a stronger signal.
    Antennas

    The folded-dipole doesn't need or want to be mounted as high as the dipole. I had trouble getting my brain around that. But this link (sort of) helped a little: Siting the antenna

    These things are so simple, they can be laid out on a piece of scrap... *anything* that's non-conductive. As long as the wire is cut to the correct length, it can be attached temporarily with tape or hot glue or tie-wraps.

    With a bit of clever camouflage, A home-owners association wouldn't even know it was there.

    (Do I sound like I'm ranting? Probably. I saved a bunch of money! )

  4. #4
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    Quote Originally Posted by sweller View Post
    I did consider a Gray-Hoverman and other types, but almost all of them are UHF. I needed a multiband antenna.
    What you could do is keep the dipole for VHF and combine a Hoverman with a UHF/VHF combiner. But as long as you're "golden" I wouldn't mess widit.

    Rick

  5. #5
    Super Moderator
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    Quote Originally Posted by sweller View Post
    ... With a bit of clever camouflage, A home-owners association wouldn't even know it was there.
    Sweller,

    Thanks to Congress, in most situations Homeowners Associations have little or no say regarding outdoor TV antennas. Details can be read at this website: Installing Consumer-Owned Antennas and Satellite Dishes | FCC.gov

    Jim : )

    PS Congratulations on your home-brew antennas and if you want to see mine, look at my photo albums here on the Forum.

 

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