Make your own low vhf antenna - AVS Forum
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post #1 of 7 Old 01-03-2010, 10:43 AM - Thread Starter
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My do it yourself low vhf antenna.

I have searched the web unsuccessfully for a simple antenna design for receiving low vhf HDTV signals (channel 3, 55 miles away). With information from ham radio sites and from (google cheap and easy tv antenna because I am not allowed to post url's), I decided on the following design based on a simple folded dipole.

Materials required:

3/4" or 1" tape measure
3/4" pvc tee
1 1/4" hose clamp - 2 ea.
foam thread spools - 2 ea.
wire - 20"
electrical tape - 12"
reusable zip ties - 2 ea.

I used these items because I had them on hand. The tape measure I used was broken but inexpensive ones can be purchased for $2.00 from harbor freight. The spools and zip ties are not required if you are going to fold your antenna or leave it extended. I prefer being able to roll it up.

Instructions:

1. Cut two pieces of the metal tape measure to length according to a cheap and easy tv antenna website. Cut the entire length first and then cut it in half because the tape measure may recoil.

2. Tape the spools to one end of each piece of the tape measure.

3. Scrape 3/4" of the paint off the other end of each piece.

4. Cut the wire in half and strip the ends.

5. Clamp everything together as seen in the pictures. Make sure the wires are contacting the scraped area of the tape measure.

6. Connect the free ends of the wires to the pick up point of your antenna. Mine can be seen attached to my coat hanger antenna.


It actually works for me. I am able to maintain a 75% signal strength for channel 3 at a distance of 55 miles.
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post #2 of 7 Old 05-06-2010, 10:05 AM
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I may be making one of these. Thanks for posting!
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post #3 of 7 Old 11-16-2013, 08:44 PM
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Brilliant post! I've been looking for something like this.

 

I live in a rural area where I'm also 55 miles from broadcast of many of the major networks. In fact, they're almost all channel 17 or below, with NBC @ 13, PBS @ 11, CBS @ 8, and ABC @ 5. With my current 4-bay homemade antenna, I can only tune in 17 and up.

 

4 questions: 

1. How long did you cut your dipoles? Looks like you're going for 1/4 wavelengths for channel 3? (About 45"per, if I'm reading your tape measure pieces correctly).

 

2. How are you attaching your PVC tee to the antenna board? I can't tell what holds it in place.

 

3. Does it matter if you cross your wire leads from your dipoles to the balun/transformer screws? I made one of those UHF 4-bay bowtie antennas, and was instructed to cross the top and bottom wires, but parallel the middle ones. Is that a consideration for the VHF dipoles, or does it matter?

 

4. You are pulling in low VHF at 55miles, which is what I'm trying to do. I haven't had much luck with a "twin lead" wire 1/2 wavelength dipole scheme I read about. Is it the surface area of the measuring tape that makes the difference? Or do you have very flat land between you and the tower? Are you using an amplifier? Is your antenna on a second storey (or higher) floor? In other words, is there anything else you're doing to get channel 3 over 55mi other than just the 1/4 WL measuring tape dipoles wired into a 4-bay UHF antenna's 300-75ohm transformer?

 

Thanks in advance if you get this message and reply!

 


Not sure if this will work, since this is my 1st post, but I'll attempt to attach an excel spreadsheet with a calculator for people who want to figure out VHF and some UHF dipole lengths for 1/2 wavelengths. (divide by 2 for 1/4 WLs, obviously). functions based on a tutorial by Rick Matthews I stumbled upon, explaining how twin-lead 300ohm antenna wires make good dipoles. It didn't work for me, or I didn't do it right. But the dipole length calculator could help someone.

 

VHF Dipole Length Calculator.xlsx 23k .xlsx file  

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post #4 of 7 Old 11-17-2013, 04:08 AM
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The OP hasn't visited the forum in a couple of years.... He may never see your questions.
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post #5 of 7 Old 11-17-2013, 05:41 AM
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Bear in mind that the OP also looks to have been in the Roanoke, VA market where WBRA-3 is on top of a very tall mountain, so even at 55 miles the line of sight may have been good. I did signal testing for someone last month at about 50 miles away from WBRA with my VHF antenna and was able to see it outdoors.

I built a VHF antenna that I find works well on upper VHF (7-13) at least, out to pretty decent distances. It also works respectably on low VHF at decent distances if placed outdoors away from noise sources (as any low-VHF antenna would need to be). I've attached some images.

Ant1.jpeg 21k .jpeg file
Ant2.jpeg 50k .jpeg file
Ant3.jpeg 64k .jpeg file
Ant4.jpeg 48k .jpeg file

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post #6 of 7 Old 11-17-2013, 08:43 AM
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Yeah, I was just hoping the OP would receive an email alert.

 

@Trip in VA:
Thanks for the info on the mountaintop tower. That would probably make a difference. My dream here is to put all antenna in my garage rafters, so max of about 10' off the ground. I do, however, live in very flat country in the upper midwest. But I suppose even curvature of the earth comes into play at 55mi. 

 

Are you certain there's no hope for tuning in channel 5 without an outdoors dipole?

  • Do my chances of tuning in a signal go up if I go from 1/2 WL dipoles to full WL dipoles? 
  • Is this idea of using twin-lead wires as a dipole a bad idea? (It sees to have a lot of foam insulation on it, if that makes a difference). 
  • On your antenna, how did you determine how long to make your elements? I notice they're longer than the usual 7-9" lengths on all the 4-bay bowtie tutorials I've seen or read.

 

Thanks for the help!

 


See attached image of my antennas. The twin lead dipole doesn't seem to do anything, but I also didn't follow directions of twisting the ends together to make a loop yet... Any tips or suggestions is much appreciated. 

 

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post #7 of 7 Old 11-17-2013, 09:44 AM
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I won't say there's no hope, but low-VHF being what it is, the noise floor goes up 20-30 dB just from being indoors around electronic devices that interfere with the low-VHF frequencies. It just means you need that much more signal to get them in usably. Attic is better than indoors, but outdoors would be best.

My elements were cut for channel 11, and I think I used the full wavelength for channel 11 as my starting point. The pictures shown were right after I made it, but now I've trimmed the ends a bit so it's somewhat shorter, but being a bowtie it's supposed to be shorter I think.

Bear in mind that a full-wavelength dipole for channel 5 will be about 12½ feet long. So I'm not sure what kind of space you have, but that's the size you'd need to make an appropriate length dipole for the full wavelength. I don't know enough about them to tell you about using the twinlead for it, though I can't imagine it would harm anything.

- Trip

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Comments are my own and not that of the FCC (my employer) or anyone else.

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