adding a reflector and director to a gainmaster ?

[BOOTY MONSTER]

ok ...... i'm having a good day <<More audio>>

one of the sweet benefits of the gainmaster is it's wide usable bandwidth . so .... if a reflector and director were added to it , should it keep its bandwidth ? i'm assuming they would need to be centered with the tuning stub in the vertical since its a center fed antenna ? would the lengths of the director and reflector need to be the standard give and take %10 of typical beams ? or would they need to be give and take %10 of the gain masters length from it's feed point at the center ?

what's your thoughts ?

 

[Marconi]

ok ...... i'm having a good day <<More audio>>

one of the sweet benefits of the gainmaster is it's wide usable bandwidth . so .... if a reflector and director were added to it , should it keep its bandwidth ? i'm assuming they would need to be centered with the tuning stub in the vertical since its a center fed antenna ? would the lengths of the director and reflector need to be the standard give and take %10 of typical beams ? or would they need to be give and take %10 of the gain masters length from it's feed point at the center ?

what's your thoughts ?

Seems you have asked a similar question before...with an A99 nearby.

I have an opinion regarding your question, but I can't tell anything about BW from modeling. I can't model the GM to show a good match, and I also can't model the choke at the bottom that makes it work so well.

Personally, I think the GM design really depends on being high and well into the clear. At my location both mounts are 36' feet apart and at least that far away from other stuff close by, trees and wires.

Here is what a center fed 22.5' foot radiator shows me with a Starduster and a A99 36' feet nearby at similar heights:

EZNEC ver. 5.0
Gain Master SD A99' 20' 2/17/2012 3:27:33 PM
--------------- SOURCE DATA ---------------
Frequency = 27.205 MHz
Source 1 Voltage = 438.4 V at 65.72 deg.
Current = 1 A at 0.0 deg.
Impedance = 180.3 + J 399.7 ohms
Power = 180.3 watts
SWR (50 ohm system) = 21.557 (75 ohm system) = 14.565

Here is the same GM with both the other antennas removed.

EZNEC ver. 5.0
Gain Master SD A99' 20' 2/17/2012 3:48:53 PM
--------------- SOURCE DATA ---------------
Frequency = 27.205 MHz
Source 1 Voltage = 436.2 V at 66.89 deg.
Current = 1 A at 0.0 deg.
Impedance = 171.2 + J 401.2 ohms
Power = 171.2 watts
SWR (50 ohm system) = 22.477 (75 ohm system) = 15.192

There's not much difference and that is probably why I don't see much affect. If you're expecting a beam like pattern to be produced, I don't think that will happen either. It may produce some kind of lopsided pattern however.

If your idea is to place the other radiators closer like a beam, then maybe you'll see some directional effect in the pattern. I'll have to check that out with the model I made for you before.

I don't think your idea about BW will be of benefit. Like a 1/2 wave dipole or an end fed 1/2 wave has a nice wide bandwidth standing alone, when they are placed close like a yagi beam, that BW may pretty much go away. So yes, IMO you'll loose the BW.

 

[Needle Bender]

Interesting idea, Booty... since the Gainmaster is a balanced center fed antenna, like a yagi driven element, I imagine you might be on to something.
Consider the Gainmaster produces the wave form with it's interesting 5/8 recurve bow current node shape, so why not add a 3%-5% smaller director element in front and a 3%-5% larger reflector element in back and have a 3 element 5/8 wave yagi?

Hey Sirio!

Booty you one belly smalt guy

 

[BOOTY MONSTER]

"Booty you one belly smalt guy"

i don't know about all that ......
but i do have a good supplier of glaucoma medicine .

 

[wavrider]

May have to look at this from a view point of resonance.

If the gain master is a 5/8 wl ( I dunno never looked at it) then it uses a matching network to get the impedance to 50 ohm.

By adding a 5% bigger reflector that reflector will need to be resonant 5% lower in frequency than the driven element ( gainmaster ).

Also the director will need to be resonant 5% higher in frequency that the gain master.

So just by adding some tubing 5% longer and 5% shorter is not going to work if the driven element is a 5/8 wl.

That is why most yagi's are either 1/2 wl driven elements or full wave length quads.

Exceptions to that are trapped yagi's and that is a whole nother ball game.

 

[AudioShockwav]

Booty is having flash backs of the old Astro beam... Lol

http://www.cbtricks.com/ant_manuals/avanti/av150/ad/index.htm




73
Jeff

 

[BOOTY MONSTER]

LOL , but that astrobeam is where folks got the idea to stick a 102 on their astroplanes in place of the stubby and tophat . might be interesting to make one with a vector basket hanging below it .

 

[Needle Bender]

May have to look at this from a view point of resonance.

If the gain master is a 5/8 wl ( I dunno never looked at it) then it uses a matching network to get the impedance to 50 ohm.

By adding a 5% bigger reflector that reflector will need to be resonant 5% lower in frequency than the driven element ( gainmaster ).

Also the director will need to be resonant 5% higher in frequency that the gain master.

So just by adding some tubing 5% longer and 5% shorter is not going to work if the driven element is a 5/8 wl.

That is why most yagi's are either 1/2 wl driven elements or full wave length quads.

Exceptions to that are trapped yagi's and that is a whole nother ball game.

Where do you get that info that "it's not going to work"?

Is there a page in the ARRL handbook dealing with a 5/8 yagi-type directional beam which states the reason it won't work to use a center fed 5/8 along with a 5/8 reflector and directors?

Since the Gainmaster sets up the balanced center fed 5/8 current distribution field, why wouldn't other 5/8 parasitic elements play against it, offering a directional effect just like a 1/2 wave yagi, since the 5/8 field is already presented by the 5/8 driven element?

Here's something you should see:

Build it, Booty!

 

[BOOTY MONSTER]

maybe some day . if i was gonna build a beam my first attempt would be using homers loop idea/example on a 2 or 3 element setup . cheaper , smaller and quieter .

 

[wavrider]

Where do you get that info that "it's not going to work"?

Is there a page in the ARRL handbook dealing with a 5/8 yagi-type directional beam which states the reason it won't work to use a center fed 5/8 along with a 5/8 reflector and directors?

Since the Gainmaster sets up the balanced center fed 5/8 current distribution field, why wouldn't other 5/8 parasitic elements play against it, offering a directional effect just like a 1/2 wave yagi, since the 5/8 field is already presented by the 5/8 driven element?

Here's something you should see:

Build it, Booty!

You might want to re read the post before you start inserting words that are not there.

I never said it would not work, I did say that the reflector and director would have to be 5% higher and lower in resonance to get any hope of having a pattern like a yagi.

Now if the builder wanted to have three (3) gain masters, with the reflector 5% lower in frequency for resonance, and the director 5% higher in frequency for resonance than it might develop a yagi type of pattern. Maybe, but would it be worth the time and expense? The weight and the wind load?

Would it be better than a half wave yagi? You would never be able to tell the difference on the receive end.

Just because an electrical length of a conductor is resonant be it wire, tubing, copper, or aluminum foil, pick your poison all will have a different length when made resonant at the same frequency. With the reflector and director there would also have to be a matching network, when dealing with something beside a 1/2 wl doublet or full wave length quad any type of antenna will have to have a matching network. the full wave loop even needs a matching network to lower the impedance.

Also you have to take into consideration mutual coupling between elements.

Since you brought the ARRL antenna hand book into the conversation why don't you provide a link to a yagi made up of 5/8 wl driven elements. I will be very interested in reading that link.

 

[wavrider]

maybe some day . if i was gonna build a beam my first attempt would be using homers loop idea/example on a 2 or 3 element setup . cheaper , smaller and quieter .

Booty yagis are fun to build and the nice thing about them is they like to work and can be made to work rather well when optimized.

EMT conduit is a cheap easy material to obtain from the big box stores, 1/2 emt is less than $2 a ten foot section and they do work for antennas real well. I have several scattered around FL and GA on the air, hard to beat a $25 four element yagi.

 

[Marconi]

LOL , but that astrobeam is where folks got the idea to stick a 102 on their astroplanes in place of the stubby and tophat . might be interesting to make one with a vector basket hanging below it .

When I made the top element of my AstroPlane a straight 1/4 wave using the 43" x 1/2" top element out of my Sigma4 attached to the 46.5" x 3/4" element of my AP, I overlapped them by 1"-4" inches using hose clamps. I got the following SWR bandwidth curve. The overall top element length was only 87.5".



I didn't sense any difference in signal when comparing these two on the same mount. If I still had my hub that I sent to Bob85, I would have built two A/P and compared them side by side too.

What kind of results did these folks get with their 102" top element? Did you ever see one? At that length I would bet they were center frequency well below channel 1. They were probably just lucky the antenna is so wide banded.

View attachment AstroPlane BW curves.pdf

Check out the difference that 3" made in center frequency.

By the way, when I replaced the top hat, the bandwidth match showed a much better match the entire range for CB and more. I didn't realize this at the time, but I did sensed better performance on air with the top hat model, even thought the signals were about the same. I think somewhere on WWRF I've already posted all about this project in 2009.

When I first got interested in this idea, was due to the image of this top element in the AstroBeam manual. It looked way short, but it was an artist rendering. I read the manual carefully and felt it indicated this full 1/4 wave element should be in the range near 79.5" inches long, and that is the length I started with in this project. That BW curve shows a center frequency of 28.000 to 29.750 mhz.

Your folks antenna probably worked, but I don't think they knew what they were really experiencing or talking about with a 102" element.

 

[Marconi]

BM, I think maybe a center fed 5/8 wave yagi design (not a GM) could be made and matched that might work as a driven element for a beam, but like someone has already said, I doubt you could tell the difference compared to a 1/2 wave. IMO, the GM has a terrible matching problem to over come, but the GM does it well...when used as intended.

My reason being, the CF 1/2 wave has an advantage in that its natural match is much closer to perfect that the match at the middle of the GM. Thus the much lower matching losses for the 1/2 wave radiator might tend to produce a better pattern and RF in this case. IMO, that alone would probably minimize any CF 5/8 wave advantage.

I think the GM design is not practical in such a beam setup due to how it uses common mode currents and the choke to handle the proximity problems with the feed line at the bottom of the vertical antenna. IMO the GM is very responsive to stuff near the bottom and needs to be well into the clear, and that might not sit too well with parasitic elements close by.

 

[Henry HPSD]

Hello Guys,

Longer element length on beam antennas have been done before.

Infact "different" shapes in order to produce more gain has also been under investigation by the pro's.

I believe, if my memory serves me rigth is that a 1,5 wl long element which looked like a S was about "optimum".

There is of course the point where the mechanical effort doesnt serve the "extra".
And the point of the entire antenna pattern.
These days normal yagi's can be made with a very very tigth FB/FR which is often of more advantage than the slightly higher gain would be.

In aspect to the 5/8 wave length... im sure if you would google edz beam, or end fed zeppelin yagi you will come up with a couple examples.

Dont worrie to much about matching in first place.
The impedance of a antenne is about the only thing we can "solve".

Kind regards,

Henry HPSD
19SD348

 

[Needle Bender]

You might want to re read the post before you start inserting words that are not there.

I never said it would not work, I did say that the reflector and director would have to be 5% higher and lower in resonance to get any hope of having a pattern like a yagi.

I'm sorry but, yes you did:

So just by adding some tubing 5% longer and 5% shorter is not going to work if the driven element is a 5/8 wl.

and the rest

Now if the builder wanted to have three (3) gain masters, with the reflector 5% lower in frequency for resonance, and the director 5% higher in frequency for resonance than it might develop a yagi type of pattern. Maybe, but would it be worth the time and expense? The weight and the wind load?

Would it be better than a half wave yagi? You would never be able to tell the difference on the receive end.

Just because an electrical length of a conductor is resonant be it wire, tubing, copper, or aluminum foil, pick your poison all will have a different length when made resonant at the same frequency. With the reflector and director there would also have to be a matching network, when dealing with something beside a 1/2 wl doublet or full wave length quad any type of antenna will have to have a matching network. the full wave loop even needs a matching network to lower the impedance.

Also you have to take into consideration mutual coupling between elements.

Since you brought the ARRL antenna hand book into the conversation why don't you provide a link to a yagi made up of 5/8 wl driven elements. I will be very interested in reading that link.

Hmm, where to start,

Regardless of the change in material, a resonant length x diameter combination will remain the same. Only the velocity factor would change the length and the velocity factor of air is so close to 1 at .9994 that it may as well be 1.

You say you would never be able to tell the difference on the other end, but if the driven element begins with 1-2dbd of gain and if that is increased by 5/8 parasitic elements, then how would you describe 2-3dbd of gain as insignificant? Never be able to tell? It might be all that is needed to barely make the contact through the noise or get over a jammer. Gain is gain and who's to say what amount it will provide until it's built and tested.
Why would you or anyone say that gain is insignificant?
Gain is gain, and I'll take all I can get.

Next you say it wouldn't be worth the size. HUH?
A 22.5' wide beam with maybe 2-3dbd gain isn't worth the extra 27" on each side? Why not? That's no mechanical nightmare, I've seen 20m yagi beams that were a lot wider than that.
Gain is gain, and who's to say that an additional 2.25'/side isn't worth the gain?
I'll take all the gain I can get.

[I misinterpreted your statement about parasitic elements needing a matching network]

What does mutual coupling have to do with the price of tea in China? Any antenna with parasitic or multiple driven elements can be in danger of mutual coupling, that's why trial and error testing and software modeling exists.

As far as having to provide you a link to a 5/8 yagi by using the ARRL handbook, this 5/8 beam idea was initiated by Booty when he began this post so why don't you tell him to do so before he ever posts another idea?

Because that would be ridiculous, just like demanding I show something in the handbook just because I challenged your offhand claim it wouldn't work. How would you know if it would work or wouldn't, have you tried it? Have you built one and tested it so you are speaking from experience or are you just saying no because it's easy to be negative?

This post is about a different idea and the possibility it might work, the onus for proof is on you who emphatically stated "It wouldn't work if the driven is a 5/8" as per above quote #1.

WTF? This isn't a pissing contest, this is about an idea of Booty's that no one knows whether or not it will work until it's tried, so what is all this negativity and nay-saying as if you already know it can't work?

If some factual info exists which demonstrates it isn't viable then show us where it is, otherwise why be so cock-sure it isn't feasible?