"Top Hat" GH with NARODs for VHF-HI: Major GH Improvement - Page 30 - Canadian TV, Computing and Home Theatre Forums

300ohm · 2011-09-11, 08:16 AM

Quote:

Meanwhile all my 3/8" reflectors and NARODS I am thinking of filling each tube with spray foam. I am thinking that this will REALLY stiffen these, although they are pretty good on their own, and be very light and have no influence on the antenna. What do you guys think?

I think it could be very messy if not very careful, heh.

But it wont have an effect on the performance, good or bad. I probably wouldnt even bother on short stand alone pieces of 18" or less.

rick5127 · 2011-09-21, 03:19 AM

Yah well the build is going quite slow. Lots of other things keep getting in the way. I just built my own idea for supports for the reflector elements. Instead of using PVC pipe and "T"'s and such I decided to use sheet plastic. Found some cutting boards at Harbor Freight that looked about right. They were about 3/8" thick and about 12" x 24". So I have been cutting them up on the bandsaw to use as supports. I took pictures but my picture editing software just crashed and the company that makes it have stopped supporting it. GRRRRrrrr so before I can edit any pictures I need to find another piece of software.

Anyways this will all make more sense when I can post the pictures on my website. I hope to have a lot of this done in the next week or so.

Still looking for a good way to clamp the two masts together as I mentioned before...

Dave Loudin · 2011-09-21, 07:44 AM

As has been noted by others, most types of plastic are not resistant to degradation from ultraviolet radiation.

rick5127 · 2011-09-21, 02:45 PM

Ok got the pictures up on the website so you can see what I meant about supports. Also revised the material list as I had made a mistake in the amounts of copper tubing I would need. Pictures are here

As far as the plastic used I plan on painting them to protect them from the sun.

Bjorn416 · 2011-09-23, 11:11 AM

Good webpage Rick - wish I knew how to make one.
I'm building the same antenna as you and noticed one gap dimension you may want to add since it's different from the one shown. Gap 4 of driven elements is 111mm as you show, but the centre gap is 109mm (call it gap 0?). For practical build purposes it may be difficult to achieve, especially if, like me, you use difficult to bend 1/4 inch T6061 aluminum rod. Trying to be helpful, not critical.

nikiml · 2011-09-23, 11:34 AM

he has it there as "feed gap" = 108.8mm

Bjorn416 · 2011-09-23, 12:09 PM

Sorry to have stirred the pot - was focused on the drawings.

rick5127 · 2011-09-23, 01:38 PM

Hey no problem with the stirring. Always good to hear constructive criticism.
My intent was just to put up some pics and info to help others when they go to build one.

Won't get to work on this till next week so no progress reports for a few days at least.

Oh and speaking of the feed point. When I finally get to it I plan on putting in the balun there. Was thinking of putting the balun behind the plane of the reflectors. But that is over 3" and I am sure the lead length will not be enough.

First off I am thinking that putting the balun behind the plane of the reflectors would do the least amount of antenna influence and that is my main goal. So since the leads will not be long enough maybe I should use some 300 ohm twin lead to connect the balun. What do you guys think?

Bjorn416 · 2011-09-25, 01:52 AM

Hope someone addresses your balun question Rick5127.
Perhaps the following questions could be addressed at the same time. I have a balun with two individual 5" solid conductor wires for attaching it to the elements. Questions:

1. should the wires, after being attached to the feed points, be brought together so the distance between them approximates that of 300 ohm twinlead?

2. assuming coax from balun will be attached to metal mast about 3" behind GH reflectors, what should orientation of the balun & wires be relative to feed points (horizontal, vertical, angled x-degrees, or ..)?

nikiml · 2011-09-25, 02:15 AM

Quote:

Originally Posted by Bjorn416

1. should the wires, after being attached to the feed points, be brought together so the distance between them approximates that of 300 ohm twinlead?

I think the answer to this question is yes.

Quote:

2. assuming coax from balun will be attached to metal mast about 3" behind GH reflectors, what should orientation of the balun & wires be relative to feed points (horizontal, vertical, angled x-degrees, or ..)?

I don't think it matters much after the balun, but I am no expert.

I think the ideal balun would be connected just as the antenna is modeled:

>----x (300ohm) x----<

here the < and > are the central bends of the active element
---- are straight horizontal wires and
the X's are the balun connection points

300ohm · 2011-09-25, 02:29 AM

Quote:

Quote:
Originally Posted by Bjorn416 View Post
1. should the wires, after being attached to the feed points, be brought together so the distance between them approximates that of 300 ohm twinlead?
I think the answer to this question is yes.

If youre going to do that, I think youll need to pay attention of the spacing depending on gauge of the extensions.
http://www.qsl.net/co8tw/openline.htm

Bjorn416 · 2011-09-25, 03:51 AM

I'm using flattend PVC electrical conduit as stand-off supports for the elements of the GH6n I'm building. They are drilled and tapped for #10-24 bolts. Also, will use notched spacers of same material to keep elements in place.

Was planning to use nylon bolts & nuts and triangle washers of the flattened PVC to attach the elements, except at the feed points. The nylon nuts would act as jam-nuts.

1. Is it ok to use metal (plated steel) bolts & nuts instead of the nylon ones? The metal bolts will not touch the elements (1/4" Al T6061 rod) - will put piece of PVC tubing on bolts if necessary.

Believe the nylon needs to be protected from UV.
2. What sticks to nylon and protects it?

Was planning to use plated steel bolts, nuts and washers at the feed points. However, have since made Al (unknown alloy) triangle washers thinking they will provide better connection between the elements, bolts and balun leads. Al washers are 3/16" thick with sides 1-3/4 x 1-1/4 x 1-1/4, same as PVC ones.

3. Is it ok to use the Al washers at the feed points, or will their mass have detremental impact on antenna performance?

300ohm · 2011-09-25, 11:27 AM

Quote:

1. Is it ok to use metal (plated steel) bolts & nuts instead of the nylon ones?

Sure, just keep them as short as possible. They can even touch the elements. With aluminum, use zinc plated or galvanized (or aluminum) nuts and bolts.

Quote:

Believe the nylon needs to be protected from UV.
2. What sticks to nylon and protects it?

Yep, white nylon doesnt last long in the sun. Spray paint will stick to it, but I dont know for how long a time.

Quote:

3. Is it ok to use the Al washers at the feed points, or will their mass have detremental impact on antenna performance?

Keep the washer end out of the feed gap area. Aluminum files very easily.

Bjorn416 · 2011-09-25, 10:19 PM

Thanks all. I’ve re-read part of Balun Thread and found picture in post 177 of a balun that looks exactly like mine: http://www.digitalhome.ca/forum/showpost.php?p=891630&postcount=177

Packaging for mine says made in Taiwan, so it should be better than one made in China, eh? Diameter of wire is 0.039" (+/- a thou) which should make it 18ga (18 being 0.0403"). Insulation is about 0.028" thick, making overall wire diameter about 0.095".

Post#179 of that thread says position/movement of wires of that balun has great impact on performance. Have read the info at the link provided by 300ohm, but if an answer to my question is there, I didn’t find it. Which do you think would be better?:

1. a narrow flat strip of black plastic (from large plant container – have lots of those) with two holes spaced equal to the spacing of the wires, as they exit balun body, at each end of the strip with the balun wires threaded thru the holes. Length of strip sized so the wires exiting the strip will be just long enough to be attached to feed point at right angles to the strip, forming a “T”.
2. shortening the wires so they are just long enough to be attached to feed point at right angles to the balun body, as illustrated by nikiml, forming a “T” with balun body.

Re keeping Al washer ends out of feed gap area: Feed gap from centre to centre of wires, or air gap from edge to edge of wires, or does it matter?

I appreciate all your help, now and when I first posted on the forum, and will post build pictures, reception results, and anything else that may be helpful to others.

300ohm · 2011-09-25, 11:05 PM

Quote:

Re keeping Al washer ends out of feed gap area: Feed gap from centre to centre of wires, or air gap from edge to edge of wires, or does it matter?

Keep it out of the air gap space.

Quote:

Which do you think would be better?:

With those "loose wire" type baluns, Ive found experimenting with wire placement, real time on the weakest channel, to be best. Sometimes, just moving the balun/wire a little bit will make a significant difference.

2011-09-21, 07:44 AM	#438
Dave Loudin Join Date: Jun 2009 Location: King George, VA Posts: 358	As has been noted by others, most types of plastic are not resistant to degradation from ultraviolet radiation. __________________ OTA, it's a beauty way to go!

2011-09-23, 11:34 AM	#441
nikiml Join Date: Dec 2008 Location: mississauga, ON Posts: 721	he has it there as "feed gap" = 108.8mm __________________ My Antenna designs, Nec optimization scripts and Web nec2 viewer

2011-09-25, 03:51 AM	#447
Bjorn416 Join Date: Apr 2011 Location: Toronto, ON Posts: 113	Attaching elements to stand-offs I'm using flattend PVC electrical conduit as stand-off supports for the elements of the GH6n I'm building. They are drilled and tapped for #10-24 bolts. Also, will use notched spacers of same material to keep elements in place. Was planning to use nylon bolts & nuts and triangle washers of the flattened PVC to attach the elements, except at the feed points. The nylon nuts would act as jam-nuts. 1. Is it ok to use metal (plated steel) bolts & nuts instead of the nylon ones? The metal bolts will not touch the elements (1/4" Al T6061 rod) - will put piece of PVC tubing on bolts if necessary. Believe the nylon needs to be protected from UV. 2. What sticks to nylon and protects it? Was planning to use plated steel bolts, nuts and washers at the feed points. However, have since made Al (unknown alloy) triangle washers thinking they will provide better connection between the elements, bolts and balun leads. Al washers are 3/16" thick with sides 1-3/4 x 1-1/4 x 1-1/4, same as PVC ones. 3. Is it ok to use the Al washers at the feed points, or will their mass have detremental impact on antenna performance?

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2011-09-21, 03:19 AM	#437
rick5127 Join Date: Aug 2011 Location: Warren, Michigan Posts: 68	Yah well the build is going quite slow. Lots of other things keep getting in the way. I just built my own idea for supports for the reflector elements. Instead of using PVC pipe and "T"'s and such I decided to use sheet plastic. Found some cutting boards at Harbor Freight that looked about right. They were about 3/8" thick and about 12" x 24". So I have been cutting them up on the bandsaw to use as supports. I took pictures but my picture editing software just crashed and the company that makes it have stopped supporting it. GRRRRrrrr so before I can edit any pictures I need to find another piece of software. Anyways this will all make more sense when I can post the pictures on my website. I hope to have a lot of this done in the next week or so. Still looking for a good way to clamp the two masts together as I mentioned before...

2011-09-21, 02:45 PM	#439
rick5127 Join Date: Aug 2011 Location: Warren, Michigan Posts: 68	Ok got the pictures up on the website so you can see what I meant about supports. Also revised the material list as I had made a mistake in the amounts of copper tubing I would need. Pictures are here As far as the plastic used I plan on painting them to protect them from the sun.

2011-09-23, 11:11 AM	#440
Bjorn416 Join Date: Apr 2011 Location: Toronto, ON Posts: 113	Good webpage Rick - wish I knew how to make one. I'm building the same antenna as you and noticed one gap dimension you may want to add since it's different from the one shown. Gap 4 of driven elements is 111mm as you show, but the centre gap is 109mm (call it gap 0?). For practical build purposes it may be difficult to achieve, especially if, like me, you use difficult to bend 1/4 inch T6061 aluminum rod. Trying to be helpful, not critical.

2011-09-23, 12:09 PM	#442
Bjorn416 Join Date: Apr 2011 Location: Toronto, ON Posts: 113	Sorry to have stirred the pot - was focused on the drawings.

2011-09-23, 01:38 PM	#443
rick5127 Join Date: Aug 2011 Location: Warren, Michigan Posts: 68	Hey no problem with the stirring. Always good to hear constructive criticism. My intent was just to put up some pics and info to help others when they go to build one. Won't get to work on this till next week so no progress reports for a few days at least. Oh and speaking of the feed point. When I finally get to it I plan on putting in the balun there. Was thinking of putting the balun behind the plane of the reflectors. But that is over 3" and I am sure the lead length will not be enough. First off I am thinking that putting the balun behind the plane of the reflectors would do the least amount of antenna influence and that is my main goal. So since the leads will not be long enough maybe I should use some 300 ohm twin lead to connect the balun. What do you guys think?

2011-09-25, 01:52 AM	#444
Bjorn416 Join Date: Apr 2011 Location: Toronto, ON Posts: 113	Hope someone addresses your balun question Rick5127. Perhaps the following questions could be addressed at the same time. I have a balun with two individual 5" solid conductor wires for attaching it to the elements. Questions: 1. should the wires, after being attached to the feed points, be brought together so the distance between them approximates that of 300 ohm twinlead? 2. assuming coax from balun will be attached to metal mast about 3" behind GH reflectors, what should orientation of the balun & wires be relative to feed points (horizontal, vertical, angled x-degrees, or ..)?

2011-09-25, 10:19 PM	#449
Bjorn416 Join Date: Apr 2011 Location: Toronto, ON Posts: 113	Thanks all. I’ve re-read part of Balun Thread and found picture in post 177 of a balun that looks exactly like mine: http://www.digitalhome.ca/forum/showpost.php?p=891630&postcount=177 Packaging for mine says made in Taiwan, so it should be better than one made in China, eh? Diameter of wire is 0.039" (+/- a thou) which should make it 18ga (18 being 0.0403"). Insulation is about 0.028" thick, making overall wire diameter about 0.095". Post#179 of that thread says position/movement of wires of that balun has great impact on performance. Have read the info at the link provided by 300ohm, but if an answer to my question is there, I didn’t find it. Which do you think would be better?: 1. a narrow flat strip of black plastic (from large plant container – have lots of those) with two holes spaced equal to the spacing of the wires, as they exit balun body, at each end of the strip with the balun wires threaded thru the holes. Length of strip sized so the wires exiting the strip will be just long enough to be attached to feed point at right angles to the strip, forming a “T”. 2. shortening the wires so they are just long enough to be attached to feed point at right angles to the balun body, as illustrated by nikiml, forming a “T” with balun body. Re keeping Al washer ends out of feed gap area: Feed gap from centre to centre of wires, or air gap from edge to edge of wires, or does it matter? I appreciate all your help, now and when I first posted on the forum, and will post build pictures, reception results, and anything else that may be helpful to others.