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Discussion Starter #1 (Edited)
Hello!

I am planning to build a mesh DBGH and am confused over what dimensions to use. 300ohm's specifications at this link differ slightly from the ones located at http://www.digitalhome.ca/ota/superantenna/design.htm. I know that the design will differ based on what frequencies I'm trying to capture.

I have had good success with stations from 70 to 130 miles away with both a Winegard 8800 stack as well as hacked XG91 stack (thanks to this thread).

The Winegard 8800 stack does not suit my application because at and above UHF 40 it sucks. Also the now somewhat end of life XG91 "hi-uhf" stack suffers on the low end due to the recent frequency transition, but was unbeatable with the higher range of UHF.

Most of the stations I want to receive now are about 70 miles away, 2 edge, channel 21 at the low end and 46 on the high end.

I'm already covered on the VHF-HI side with a Funke 1922, so I'm not concered with the DBGH being able to receive those frequencies.

Any guidance is much appreciated on which set of measurements for the mesh design I need to use for the DBGH that would work best for UHF 21 though 46 before I embark on this endeavor.
 

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Would these be the correct plans to use?
No, thats Autofils GH10, which has a steep drop off after about channel 42.

You want to use the dimensions from the first link you had, located at http://www.digitalhome.ca/ota/superantenna/design.htm.

and for extra gain, use a 89mm feedpoint gap, and a a 2 inch phasing line gap.
Also remember to have a 1 inch vertical gap in the mesh.
 

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Discussion Starter #6
It turns out I don't have two continuous pieces of 1"x1" wire mesh on hand that are 80" tall and 15" wide. I was able to make two of that size by patching several squares of mesh together and affixing with black plastic tie wraps.

Do you think it will matter much to the performance if I had to splice several pieces of mesh together on the vertical axis? And keeping the 1" gap between the two "patched" together pieces?

Or should I go out and find some longer pieces of mesh?

Thanks again!!!

It's almost built!!! I just need to figure out your slip on tee method, 300ohm - I'm having trouble making it fit in snugly enough without requiring hardware or glue.

Then bend my elements, attach with the hardware and glue everything up. A fresh coat of grey primer afterwards.
 

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Or should I go out and find some longer pieces of mesh?
No, youll be fine if you have a good electrical and physical connection of the mesh pieces.

I just need to figure out your slip on tee method, 300ohm - I'm having trouble making it fit in snugly enough without requiring hardware or glue.
The cut has to the just the right size, which with a little practice becomes easy. I draw the lines on the tee with a common number 2 pencil on a flat surface (and the tee being on the flat surface too.)

Also, rather than glue, a tiny #4 X 1/2" screw can hold a loose slip on tee in place, and can be removed or adjusted later.
 

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Discussion Starter #8 (Edited)
Speaking about a DBGH here.

I've read over these threads several times and have a few nagging concerns before I bend the elements and phasing lines.

I know it's nit-picky - and I'm not trying to mince words here - but when I see the words "millimeter precison" written I usually like to measure 8 times and cut twice.

1.) This post http://www.digitalhome.ca/forum/showpost.php?p=767687&postcount=8 calls for an element .5" inches shorter than this website http://www.digitalhome.ca/ota/superantenna/design.htm

2.) This post http://www.digitalhome.ca/forum/showpost.php?p=776553&postcount=28 says a common 16 penny nail with a 10 gauge wire looped around it adds 1" to the length of the element or phasing line. It does not add that much - only about .8 inches - and as far as I can calculate you would need a 20 penny common nail wth .148" diameter to get 1" more. But I'm guessing that aside from the math above the goal here is to not increase or decrease the length of the element or phasing line with any loops to accommodate mounting hardware (which is somewhat in question per point 1 above). Again, I understand different designs will yield different reception results.

3.) IF I stick to the goal of not decreasing or increasing the length of the element once I can confirm the proper dimensions, I am guessing it is safe to add the loops to the elements AS WELL AS the phasing lines for a more secure fastening option at the balun/combining points.

4.)
and for extra gain, use a 89mm feedpoint gap
Assuming that is center to center on the element wire, and NOT taking element gauge into account? For example with 6 gauge I would use 89mm or for 10 gauge I would still use 89mm.

5.)
and a a 2 inch phasing line gap.
With a 89mm or 3.5 inch gap between the elements (also feedpoints for balun), in order to achieve a 2" gap, the phasing lines will need to "bend inwards" after bending to the Z axis by 1" to achieve a 2" gap. Is this correct?

Thanks again! This is great fun! :)
 

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No, 142 mm is 5.5905511 inches, so since no one can measure that close, I used 5.6 inches.
180 mm is 7.0866141 inches, so with the bend, 7.0 inches covers that.
2.) This post http://www.digitalhome.ca/forum/show...3&postcount=28 says a common 16 penny nail with a 10 gauge wire looped around it adds 1" to the length of the element or phasing line. It does not add that much - only about .8 inches - and as far as I can calculate you would need a 20 penny common nail wth .148" diameter to get 1" more. But I'm guessing that aside from the math above the goal here is to not increase or decrease the length of the element or phasing line with any loops to accommodate mounting hardware (which is somewhat in question per point 1 above). Again, I understand different designs will yield different reception results.
3.) IF I stick to the goal of not decreasing or increasing the length of the element once I can confirm the proper dimensions, I am guessing it is safe to add the loops to the elements AS WELL AS the phasing lines for a more secure fastening option at the balun/combining points.
You dont have to have a loop, you could solder tabs in the middle like I did on a later phasing line. The important thing is to have the phasing lines exactly the same length and symetrical.
.)
Quote:
and for extra gain, use a 89mm feedpoint gap
Assuming that is center to center on the element wire, and NOT taking element gauge into account? For example with 6 gauge I would use 89mm or for 10 gauge I would still use 89mm.
The 89mm distance I used was the distance across one of my tees when wire was abutted to it. This makes a great stop edge for the wire. The actual sweet spot for more gain is like from 80mm to 105 mm IIRC, so theres a lot of room for different tees (Ive found that different makes are slightly different). And even at the original 44 mm distance, the antenna still works fine, as the difference is only like .2 - .3 dbi.
With a 89mm or 3.5 inch gap between the elements (also feedpoints for balun), in order to achieve a 2" gap, the phasing lines will need to "bend inwards" after bending to the Z axis by 1" to achieve a 2" gap. Is this correct?
Yes, exactly. And when I set up a real time measuring system, Ill experiment with bending in the phasing lines like mclapp does on his 8 bay to see if I can lower the SWR even more.
I usually like to measure 8 times and cut twice.
Heh, same here, so keep asking if youre confused about something. The DBGH with mesh is relatively easy and foolproof to get about 17 dbi top gain. :)
 
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