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-   -   Has anyone made a 300 ohm twin lead antenna? (http://forum.tvfool.com/showthread.php?t=16222)

VTME09 10-Feb-2017 12:42 PM

Has anyone made a 300 ohm twin lead antenna?
 
Has anyone made one of these antennas for a single channel from 300 ohm twin lead? How well did it work? I want to get channel 3.
http://users.wfu.edu/matthews/misc/dipole.html

rickbb 10-Feb-2017 2:29 PM

They work well enough, but how will you mount it? They need to be "aimed" at the tower so it works best up on the roof and getting it on some kind of non-metal mount will be tricky.

One of these for real channel 3 will be just over 6 feet long.

You can buy a low VHF, (assuming you mean real channel 3), antenna very cheaply, BTW.

VTME09 10-Feb-2017 3:02 PM

I have seen some people have supported them in a PVC tune and was thinking about doing that and suspending it in the attic where size wouldn't matter.

I currently have a Antennas Direct High VHF antenna and it picks up real channel 3 (~50 miles away) in the winter only. I pointed it at channel 11 (5 deg mag ~50 miles away) thinking I couldn't get 3 (260 deg mag) but after the leaves fell I could. So I am expecting to loose it again come spring. My zip code is 24503.

What VHF Low antenna do you recommend? I have been looking at the Winegard HD7000R but it's only rated for 30 miles.

ADTech 10-Feb-2017 4:13 PM

Quote:

What VHF Low antenna do you recommend?
There aren't any VHF low antennas on the market any longer so your choices are very limited. We liquidated our remaining inventory of the V4 antenna a while back, I think these guys might still have them: https://www.affordablehdtv.com/terre...8ofsvgsqj1ian2 The V4 is a cut-to-channel 4 Yagi and is effective for channels 2, 3, & 4. Not so much on 5 and poorly on 6 and FM. If you needed 5 or 6 or FM, I think our old 3FM antenna (which we also liquidated inventory of) can still be found on Amazon.

If you do add in a low-band VHF antenna, you'll still need to score an HLSJ in order to readily combine it with the rest of your setup and they're getting very scarce. I did find a listing on ebay, do a search for "CABLETRONIX HLSJ". I've not tested that particular one, but it should work based on the manufacturer's spec sheet.

Quote:

I have a Antennas Direct High VHF antenna and it picks up real channel 3
If you have the C5, it's tuned very precisely for high-VHF channels 7-13 and does a remarkable job of rejecting low-VHF and FM frequencies (it is supposed to do that by design), probably in the order of -15 to -20 dB or so on channel 3.

If you have a suitable length of 2-conductor heavy electrical wire 12-14 ga, insulated or not) and a common matching transformer (https://www.lowes.com/pd/RCA-Outdoor...former/3724168), you can easily fabricate a simple dipole without trying to find twin-lead. Use two 4'3" sections of wire attached to a simple frame of wood or PVC with a 1-2" gap between them and attach each leg of the transformer to the inside ends of the gap with a simple sheet metal screws. Aim it broadside in the direction of WBRA, then adjust for best results.

VTME09 10-Feb-2017 6:13 PM

I have a DB8E with a VHF-1 retrofit kit.

Found a 100 feet of twin lead online at Fry's, ~10$ delivered. Would the twin lead or electrical wire be better?

ADTech 10-Feb-2017 6:40 PM

If you have a matching transformer (which you're going to need anyway) and some wire, why buy twin-lead? There won't be any difference in performance if executed properly.

VTME09 11-Feb-2017 2:01 AM

What is the range on the Antennas Direct V4? I see two places that say 25 miles and the link ADTech sent says 55 miles.

ADTech 11-Feb-2017 1:06 PM

It is my personal opinion that range numbers are an irrelevant but a necessary evil. At best, they're only a wild-a$$ guess. There are too many other variables that are actually more important than the antenna itself that are involved in determining if any given antenna is suitable for any given situation They're pretty much a lowest common denominator for folks for whom a mile is the only thing they can relate to.

rabbit73 11-Feb-2017 3:52 PM

2 Attachment(s)
I agree; mileage figures are only useful to compare different models of the same brand. What counts is how strong the signals are at your location, and putting it in the attic makes them even weaker. What good is a 55 mile antenna if you happen to have a hill five miles away that blocks the signals?
Quote:

Has anyone made a 300 ohm twin lead antenna?
Yes, the twin lead folded dipole is one of my favorite antennas.

Many years ago I was located between Richmond and Norfolk. In my attic I had a folded dipole or a 5 element single channel yagi cut for each channel. I had a 2-pole, 12 position ceramic switch with its shaft extended below so that I could select which antenna I needed. It worked very well. All the feed lines were 300 ohm twin lead, which is why I used a 2-pole rotary switch.

At my next location, I only used the Norfolk channels. I had a 4-bay UHF antenna and a folded dipole for 13 connected to the original 7777 preamp that had separate inputs for UHF and VHF. The antennas were only 5 feet AGL, but reception was satisfactory. The UHF and VHF channels were about the same strength on my report, but 13 was weaker for me because of the lower gain of the folded dipole.

At my present location I am closer to Norfolk and am able to use a GE 34792 Attic Antenna indoors at ground level. Channel 13 is again weaker because the GE antenna only has a single element folded dipole for VHF-High. The UHF section has more gain, so I can get PBS on 16 which has Create, one of my favorites.

http://forum.tvfool.com/attachment.p...1&d=1486828373

You can suspend a twin lead folded dipole for channel 3 in your attic to see how it works.

http://forum.tvfool.com/attachment.p...1&d=1486829832

Channel 3, 60 to 66 MHZ, center frequency 63 MHz

5540/63 = 87.9 inches length for a folded dipole antenna

rabbit73 11-Feb-2017 9:23 PM

1 Attachment(s)
To convert the dipole antenna into a 3 element beam for more gain, add a reflector and a director:

Wire Reflector, 92.3 inches,

Wire Director, 83.5 inches,

dipole to reflector spacing is 37.49 inches

dipole to director spacing is 28.12 inches

http://forum.tvfool.com/attachment.p...1&d=1486848071

VTME09 26-Feb-2017 7:04 PM

On channel real 3 I got 4 out of 10 signal strength with the twin lead and matching transformer mounted on a piece of wood in my den, in a brick house looking out a window. I am assuming it will drop some in the attic and summer with leafs also.

Is it almost certain that something like the AD V4 will work better?

ADTech, you mentioned the V4 is a cut to channel antenna, do you trim all three components? What is the difference between the V4 and Winegard HD7000R?

Is there an advantage to a full wavelength vs 1/2 wavelength antenna?

I found a well priced VHF High and Low combiner. https://www.solidsignal.com/m/product.aspx?p=zhlsj

rabbit73 27-Feb-2017 12:10 AM

1 Attachment(s)
Quote:

Is it almost certain that something like the AD V4 will work better?
Nothing is certain with an attic and trees involved. You just have to try it. It does have more gain than a folded dipole, and about the same as a 3-element wire yagi, but it might not be enough for WBRA. Do you have room for an antenna that is about 10 feet wide with a 5 foot boom?
Quote:

ADTech, you mentioned the V4 is a cut to channel antenna, do you trim all three components?
You don't trim anything. The term "cut to" means that the V4 was designed to work on channels 2-6, but the best on CH4.
Quote:

What is the difference between the V4 and Winegard HD7000R?
The V4 is designed for VHF-Low, real channels 2-6, and has more gain on that band than the 7000R. The 7000R is designed for all three TV bands, and doesn't have a lot of gain on any of them.
Quote:

Is there an advantage to a full wavelength vs 1/2 wavelength antenna?
A fullwave dipole has little more gain than a halfwave dipole, but it is twice as long. For channel 3, it would be 16 feet long instead of 8 feet. We see fullwave dipoles in UHF bowtie antennas that have fullwave dipoles for each bay. A fullwave dipole is often called a collinear pair, because it has two halfwave dipoles in line side-by-side. The bowtie antenna is derived from the collinear array.

http://i496.photobucket.com/albums/r...psrxqzi62s.jpg

http://i496.photobucket.com/albums/r...psfnpknksg.jpg

http://i496.photobucket.com/albums/r...urrentFlow.jpg

We also see fullwave elements in UHF and VHF loop antennas. Think of it as a folded dipole that has been opened up to form a circle, rectangle, or square. The folded dipole has two halfwave wires connected at the ends.

The most interesting fullwave loop antenna is the element used in Antennas Direct UHF antennas. Think of it as a fullwave dipole that has fat ends to increase the bandwidth, the way that whiskers increase the bandwidth in the bowtie antenna. Then, imagine that the ends are bent up to meet each other and join. This creates a tapered loop. Don't make one to sell, Antennas Direct holds the patent.

http://forum.tvfool.com/attachment.p...1&d=1488153777

Instead of a 3 element ch 3 yagi, you could make a 3 element quad antenna, with 3 fullwave loops, 1/4 wave on each side, about 45 inches. The director loop would be a little smaller and the reflector loop a little larger.

rabbit73 27-Feb-2017 1:11 AM

Quote:

I found a well priced VHF High and Low combiner.
That looks good.

I see that you have a previous thread. It would have been better to add your question to that thread instead of starting a new one, which would give us the background information, making it easier to help you.

Reception Help
http://forum.tvfool.com/showthread.php?t=16134

and the report
http://www.tvfool.com/?option=com_wr...dfaf2e0205f846

It was suggested that you try for WVPT PBS on channel 11 with a VHF-High antenna that has more gain than the VHF dipole kit for your DB8e. Did you try that idea?

VTME09 27-Feb-2017 1:37 AM

Since then I have found out they have different programming and decided to go for both. Sorry this went from a a question about the twin lead to a lot more.

rabbit73 27-Feb-2017 2:02 AM

Quote:

Sorry this went from a a question about the twin lead to a lot more.
No problem; we got to what you wanted anyway.

Quote:

Since then I have found out they have different programming and decided to go for both.
Right

WBRA
http://www.rabbitears.info/market.ph...&callsign=wbra

WVPT (my favorite; Create with travel and This Old House)
http://www.rabbitears.info/market.ph...&callsign=wvpt

Please let us know how it works out, on this thread.


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