Antenna Experts, Please chime in!!

[Dmans]

So since my antenna rotor has been broken since last September, I had some time (caught up on the “Honey Do List”) to drop the mast to replace it.

My mast is a 40’ 1 1/2” water pipe attached to a 6 x 6 concreted in the ground and bracketed to the house at the 20’ and 35’ heights. It is mounted to the 6 x 6 with 2 1/2” bolts so can lean it away from the house for maintenance. This is done with ropes and about 16 pulleys to make it easier on me. Yesterday I let the rope slide through my hand and some damage ensued. The vertical VHF antenna snapped and the 3 element Hygain (horizontally mounted) suffered some damage. The 2/440 antenna was an easy fix.
The Hygain is where the question comes in.
This Hygain (LJ113) has 3 sections of tubing on each side of the boom. The largest diameter is 7/8” (attached to the boom) and has a “ double swage” whereby the middle section is 5/8” diameter and it has a “double swage” too whereby the outer element is 7/16” diameter.
I will have to replace some aluminum tubing but don’t want to replace the antenna completely. ( Purchase price $139.00- Todays price $359.00)
Since I have to replace some tubing, if I used 7/8” tubing for the inner element, 3/4” for the middle element and 5/8” for the outer element, will this increase the bandwidth of the antenna? Or should all elements have to be “upsized” to see any real benefit?
I use the Hygain on both 10 & 11 meters and I am thinking since I have to replace some tubing, can I improve the antenna at the same time?
All information is appreciated.

73
David

Edited to add:
I am talking about upsizing the driven element. I can salvage enough tubing to replace the Director and Reflector elements with the “stock” sizes.

 

[Eldorado828]

So since my antenna rotor has been broken since last September, I had some time (caught up on the “Honey Do List”) to drop the mast to replace it.

My mast is a 40’ 1 1/2” water pipe attached to a 6 x 6 concreted in the ground and bracketed to the house at the 20’ and 35’ heights. It is mounted to the 6 x 6 with 2 1/2” bolts so can lean it away from the house for maintenance. This is done with ropes and about 16 pulleys to make it easier on me. Yesterday I let the rope slide through my hand and some damage ensued. The vertical VHF antenna snapped and the 3 element Hygain (horizontally mounted) suffered some damage. The 2/440 antenna was an easy fix.
The Hygain is where the question comes in.
This Hygain (LJ113) has 3 sections of tubing on each side of the boom. The largest diameter is 7/8” (attached to the boom) and has a “ double swage” whereby the middle section is 5/8” diameter and it has a “double swage” too whereby the outer element is 7/16” diameter.
I will have to replace some aluminum tubing but don’t want to replace the antenna completely. ( Purchase price $139.00- Todays price $359.00)
Since I have to replace some tubing, if I used 7/8” tubing for the inner element, 3/4” for the middle element and 5/8” for the outer element, will this increase the bandwidth of the antenna? Or should all elements have to be “upsized” to see any real benefit?
I use the Hygain on both 10 & 11 meters and I am thinking since I have to replace some tubing, can I improve the antenna at the same time?
All information is appreciated.

73
David

Dang that's a bummer right there. No rope burns or hand injuries, hopefully not. I bet that got your heart rate up.

 

[Dmans]

Dang that's a bummer right there. No rope burns or hand injuries, hopefully not. I bet that got your heart rate up.

Yes a bummer!! No rope burns, no aluminum tubing in the eye either.
I forgot to mention in the above post that the accident also snapped my 1:1 Current balun as well.

 

[26OD004]

With the change in size you're talking about, you will notice no difference. You may find you need to shorten the driven element a tiny amount to make it resonate where the old one did but that's all. It's all relative to wave length, increasing element diameter by even 1 inch when the wavelength is 36 feet will make little difference to the bandwidth.

 

[Dmans]

With the change in size you're talking about, you will notice no difference. You may find you need to shorten the driven element a tiny amount to make it resonate where the old one did but that's all. It's all relative to wave length, increasing element diameter by even 1 inch when the wavelength is 36 feet will make little difference to the bandwidth.

This is an example of the “double swage” as I called I called it. In retrospect, I guess it is just swaged.
Below from the 1st element (attached to the boom) to the middle element.

Below from the middle tube to the outer tube.

I was lead to believe or read it somewhere that the larger the element, the greater bandwidth available. Is that just on the dipole (or driven element) or do all the elements need to be the same diameter?

I am trying to not wrap a bunch of money in this project. The antenna was initially tuned to 28.400 MHz but I am trying to reach the 11 meter band with a little better match/resonance.

73
David

 

[26OD004]

You are correct in what you have learned, the larger diameter element will give more bandwidth than a smaller diameter element, the only question is, how much?

In relation to the wavelength you are operating on the element diameter is changing by a miniscule fraction.

In short, just repair the broken parts of the antenna with what you have, you won't notice any difference apart from the antenna will work correctly again.

 

[Dmans]

You are correct in what you have learned, the larger diameter element will give more bandwidth than a smaller diameter element, the only question is, how much?

In relation to the wavelength you are operating on the element diameter is changing a by a miniscule fraction.

In short, just repair the broken parts of the antenna with what you have, you won't notice any difference apart from the antenna will work correctly again.

Actually, for what aluminum I will have to buy, going to a larger diameter for the middle and end sections (I can cut the swaged portion out of the boom mounted element) may make a difference in performance and very little difference in price of the 5/8” and 7/16” elements vs. going to 3/4” and 5/8” elements.

73
David

 

[Crawdad]

I certainly don't claim to be an expert, but modelling the antenna would be one way to gauge how much bandwidth increase you might gain but I don't think you'll see very much. Doubtful the changes will get you down a MHz if you couldn't get there before without a tuner.

7 3

 

[Beetle]

Those rivets make me nervous, especially on aluminum. Should be stainless steel hardware, including lockwashers.

IMHO, of course.

 

[Dmans]

Those rivets make me nervous, especially on aluminum. Should be stainless steel hardware, including lockwashers.

IMHO, of course.

I did notice the sections have some play in them with the rivets holding them. I will either remove the rivets completely and add TRUE stainless clamps or add the stainless clamps in addition to the rivets.
The plan is to disassemble the entire antenna, give it a good cleaning and re-assemble it with the same measurements.
It has been assembled and in the air for 10 years now and has maintained the tune it was set up with. (And it has occasionally experienced more input power than the manual specified-accidentally of course)
I will put the Antenna Analyzer on it before disassembling just to verify a few settings. (I didn’t have an analyzer when first putting this antenna together)

73
David

 

[Crawdad]

I did notice the sections have some play in them with the rivets holding them. I will either remove the rivets completely and add TRUE stainless clamps or add the stainless clamps in addition to the rivets.
The plan is to disassemble the entire antenna, give it a good cleaning and re-assemble it with the same measurements.
It has been assembled and in the air for 10 years now and has maintained the tune it was set up with. (And it has occasionally experienced more input power than the manual specified-accidentally of course)
I will put the Antenna Analyzer on it before disassembling just to verify a few settings. (I didn’t have an analyzer when first putting this antenna together)

73
David

Curious as to how your project worked out and were you able to tune it for 11m as well as 10m?

7 3

 

[Dmans]

Crawdad,
I finished it last weekend and haven’t transmitted on it once. I tuned it to resonance at 28.400 with the mast laid over and the reflector about 6’ off the ground. It very usable for all of 10 meters. See Nano
VNA display below.

After raising the mast to full height, I get an SWR of 1.5-1.7 at 27.385. No issue using it there. If I want to go lower in frequency, I have an outboard tuner.
I did remove all of the rivets and used stainless hose clamps on the elements. I did not use any larger tubing. With some straightening, all of the original tubing was usable.

Below is the finished product. I am liking the HD-73 rotor and if the afternoon lightning storms stop I will have to give it serious work out.

I now need to get back to some work bench projects. I have a particular “Frankenstein” project to finish up and a 2970 to straighten out.

73
David

 

[Crawdad]

Looking great David and sounds like it will cover the bandspace you were hoping to cover. Glad to hear it!

7 3 and good DXing