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Old 2009-02-05, 07:43 PM   #16
balm
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Default bow-tie help

Anyone:

Any comments for changes to my DYI bow tie antenna for improved channel reception in the west island (Pointe-Claire), or should I scrap and build anew!

Thanks



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Old 2009-02-06, 01:11 PM   #17
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What dimensions did you use?

It looks like the V shaped whiskers are spaced too close together vertically and too far apart horizontally.

It's also best to use some sort of plastic spacer so the antenna elements are not directly mounted to the wood.
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Old 2009-02-06, 10:24 PM   #18
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mclapp:

whiskers are spaced at 5 3/4" in the vertical and 3" in the horizontal, they are 7 1/2" long - I know, I'm guilty, I copied the youtube, just to try - guess I was lucky that it got me all the US HD channels (UHF of course) and 2 of the 3 local HD channels!

My understanding is that I should have calculated the whisker length as follows:

- take the highest available channel wanted (#53, CBS) frequency - 700 Mhz
- calculate (300/700) x 1/2 = .214 m = 8.4"

calculate whisker vertical separation = say 8.4" - .4" = 8"

use whisker horizontal separation = 1 3/8"

use 10 gauge wire for the whiskers and lines, is that optimal?

I know I have many details, connections, stand-offs to improve...

also I noted that the reflector (24" x 30") did not improve my reception capabilites too much in any direction...

Does this make any sense, or should I try your 9.5" x 9" plans

Now that I am gaining more knowledge about the physics, thanks to people like you, I am addicted and have found a new hobby!

I plan on making a better version, or maybe build another type (SBGH..)

thanks for the HELP

Last edited by balm; 2009-02-06 at 10:34 PM. Reason: more details
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Old 2009-02-07, 11:26 AM   #19
The Antinuator
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Default bow tie help

where your wires cross one of them must be insulated or it will camcell out the signal
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Old 2009-02-07, 01:24 PM   #20
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antinuator:

I allowed a 1" separation between the two instead. Thanks
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Old 2009-02-08, 04:43 AM   #21
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Balm,

the 9 1/2 x 9 covers the UHF band up to ch45 quite well but after that it starts to lose gain. If your stations above 45 are fairly strong it shouldn't be a problem. If you need more gain up high the just resclae the whisker length and phase line vertical spacings a little shorter like 9 x 8 1/2".

A reflector should make a noticable difference on your weaker stations it should be spaced 4" behind the elements for best UHF reception. 10 gauge wire should be fine for the whisker elements and will work for the phase lines but 14 or 16 gauge is better for the phase lines, not so much for gain but for the sake of cost and ease of construction.
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Old 2009-02-09, 12:17 AM   #22
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mclapp:

Thanks. That is what I have done. I am now building a better model.

REGARDING MY NEW MODEL:

A) In your experience or studies how critical is vertical planity (in the z-axis)- for the following components, if you could comment each:

1- whiskers relative to phase lines (placing the whisker on top of phase line, instead of placing whisker bend adjacent (same elevation) to phase line);

2- one phase line relative to the other (if one is more elevated than the other);

3- cross-over points (uneven - one bridging over the other and/or one undercutting the other) - at one end I have one phase line bridged up and over the other (about 1/2" up and out of the plane of the phase lines), at the other end it's the opposite, I have one phase line passing beneath the other (about 1/2" under the plane of the phase lines)


B) How critical the location of the phase line cross-over relative to the top and bottom whisker connections (in the y-axis) - I saw a dimension of 2 1/4" to start of bends, 2 1/2" in the diagonals


C) What is the simplest, and/or optimal method of connecting the balun to the phase lines. Also is it always best to avoid using stand-offs and bolt connections for this.

I will probably ask you some questions later on about the reflector method, dimensions, but first I will study up!

Thanks for your patience...
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Old 2009-02-09, 10:53 PM   #23
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Default Pointe_claire - new model

mclapp:

This is my new bow-tie (9 1/2 x 9):




1) can now pick up digital WVNY - ABC channel # 13, at 30 ft height, cannot lock properly below this height, any ideas how to ensure a lock at say 26 ft, preamp, reflector, longer whiskers etc...

2) lost local digital channel # 42, seems to respomd better with reflector...

3) Still cannot get local digital CBC channel # 19 or # 20, Mount Royal blocks most of the signal, however I did notice improvement here too, TV shows a 30-40% strength, compared to 10-20%...any ideas for this, as in bullet 1) above....

Thanks
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Old 2009-02-09, 10:58 PM   #24
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Quote:
Originally Posted by balm View Post
mclapp:

Thanks. That is what I have done. I am now building a better model.

REGARDING MY NEW MODEL:

A) In your experience or studies how critical is vertical planity (in the z-axis)- for the following components, if you could comment each:

1- whiskers relative to phase lines (placing the whisker on top of phase line, instead of placing whisker bend adjacent (same elevation) to phase line);
Not sure what you're asking here but it's best to have the phase line to whisker connection so that the whiskers don't overlap too much, just enough to make a good connection. I've modeled the connection point where the whisker bend makes connection for more than 1/4" and it doesn't show any real difference.
Quote:
2- one phase line relative to the other (if one is more elevated than the other);

3- cross-over points (uneven - one bridging over the other and/or one undercutting the other) - at one end I have one phase line bridged up and over the other (about 1/2" up and out of the plane of the phase lines), at the other end it's the opposite, I have one phase line passing beneath the other (about 1/2" under the plane of the phase lines)


B) How critical the location of the phase line cross-over relative to the top and bottom whisker connections (in the y-axis) - I saw a dimension of 2 1/4" to start of bends, 2 1/2" in the diagonals
The key thing to remember is that the phase line is just a feed line that attaches the whisker elements in phase. Try to keep the phase line wire spaced evenly apart at all points and keep both wires the same length between elements. This can't be done by just looping one wire over the other because you'll end up with one wire longer than the other and that element will be sligthly out of phase with the others. Where the wires actually cross in between the elements is not critical. I've found that a simple twist in the middle works as good as anything.




Quote:
C) What is the simplest, and/or optimal method of connecting the balun to the phase lines. Also is it always best to avoid using stand-offs and bolt connections for this.

I will probably ask you some questions later on about the reflector method, dimensions, but first I will study up!

Thanks for your patience...
You can attach the balun to the phase lines the same way as you do the whisker elements with screws and standoffs. I prefer to attach my balun/feedline directly to the phase line by soldering and not use any screws or stand offs but that's not a must and they have worked fine either way.
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Old 2009-02-09, 11:16 PM   #25
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You must have posted your latest build while I was posting the answers to your previous questions. Your build looks really nice those cross overs look fine from what I see in the picture. A reflector will gain you about 2-4 db on most channels.

To improve VHF-hi a 32" wide or larger reflector will be required. It could be simple rods spaced 3-4" apart vertically or some sort of wire fencing or hardware cloth with a vertical spacing of 3" or less.

The reflector should be spaced 4" behind the elements for channel 13 and UHF channels if you are using the 9 1/2" x 9" size elements and phase line dimensions.

You can squeeze a little more UHF gain out of it by sweeping forward the elements 2" and building a dished/curved reflector with about 2 1/2 to 3" of curve for a 36" wide reflector.

Heres an example of the curve how you do it is up to you, I'll also include a picture of an angled reflector that also works well but doesn't produce as even of a gain across the UHF channels but is still an improvement over a flat reflector. Neither the curve or angled reflector has any advantage over a flat reflector on VHF-HI



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Old 2009-02-10, 09:31 AM   #26
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mclapp:

Thanks for the replies and close-ups.

you mention spacing rods 3-4" apart vertically, wheras with wire meshing to use 3" or less, why is the difference between the two, I assume it is due to the the larger diameter of the rods vs mesh...

thanks again
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Old 2009-02-10, 09:52 AM   #27
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Very nicely built Balm

I am amazed you catch WVNY with that antenna, you must have a clear view towards Lac St-Louis on the south?

your antenna is mounted 30-ft high on a tower?
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Old 2009-02-10, 12:31 PM   #28
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Yes due to the larger diameter of the rods or tubing you can get away with slightly larger vertical spacing. If using tubing or rods for reflector elements I found to get maximum gain for minimum elements it's best to put 2 reflector rods centered behind each whisker about 3 - 3 1/2"" apart like this.



This antenna uses single flat elements instead of whiskers but the same reflector layout could be used for either.

Forward gain isn't much different between this tubing reflector layout and 1" mesh but the rear rejection for the tubing reflector is not nearly as good on UHF.
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Old 2009-02-10, 05:17 PM   #29
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hungt1999:

yes, I was amazed also.

I temporarily put 12 ft ABS pipe into another ABS pipe running up the outside wall of the townhouse, and from the second floor window, this was for testing only - it is way too dangerous as it sways easily - I have since lowered it by some 10 ft.

I have since added a 32" x 40' reflector mesh at 4" depth, and I was able to get CBMT (CBC english -local digital channel #20 - intermittently) and intermittently WVNY digital - I was extremely surprised to get CBC, as it is blocked by Mount Royal to the west. As for WVNY I am surrounded by 3 and 4 story apartment blocks, however still get all Mount Mansfield channels in digital.


I am near Des Sources and Highway 20

Now I would like to improve on the reflector, and get a higher, permanent installation.

I think I will need to improve the antenna or maybe build another type to secure CBC, WVNY, and TQS - I 'm not sure about adding hardware, preamp?


thanks
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Old 2009-02-10, 06:53 PM   #30
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Quote:
I temporarily put 12 ft ABS pipe into another ABS pipe running up the outside wall of the townhouse, and from the second floor window, this was for testing only - it is way too dangerous as it sways easily - I have since lowered it by some 10 ft.
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