5/8 dipole used as driven element on a beam ?

[BOOTY MONSTER]

just thinking .........

could a 5/8 center fed dipole (similar to the gainmaster) be used as the driven element on a beam ? im guessing the reflector and director(s) would have to be longer because of the physical length of the driven element . since the gainmaster is supposed to have 1 or 2 db of gain over other 5/8's and a typical 5/8 had 1.5 db of gain over a typical 1/2 wl dipole would there be 2 1/2 to 3 1/2 db of gain over a typical beam with the same number of elements ? would the broad bandness of the gainmaster also benefit a beam based on it ?

im guessing the extra 4 ft of length over typical 18ish ft elements is a fair trade off for a extra 2 1/2 to 3 1/2 db of gain . heck some cbers might like that its a bigger more imposing looking antenna , LOL . i wonder if sirio has any plans to release a beam like this ... ? it would probally cost $200 more than a typical beam with the same number of elements though ........ coax and fiberglass is expensive :bdh:

am i onto something ???? or just showing my stupidity again ?

 

[Robb]

I think it would, so long as the reflector and driven elements are proportional as well.
Be interesting if Henry HPSD would comment on this.
Loading and tuning it would be the issues.
op:

 

[wavrider]

op:op:op:


How would the reflector and directors be made to work using an unbalanced driven element?

 

[Robb]

op:

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How would the reflector and directors be made to work using an unbalanced driven element?

Prolly a 15m beam tuned on 11m - lol!
Spacing would be all wrong.
op:op:op:

 

[wavrider]

op:

Prolly a 15m beam tuned on 11m - lol!
Spacing would be all wrong.
op:op:op:

I had the same idea as booty and pondered it around, as the logic seems to make sense until it is time to construct it.

the 5% longer rule for reflector actually puts it 5% lower in frequency resonance compared to the driven element, it would be a PITA to build a yagi like that.

On the other hand I also pondered a ground mounted two element vertical array for the lower bands, driven and director. .625 driven element then a 5% smaller director spaced .25 wl in front of the driven element, might work good for 40 meters. I thought about it, but will probably never experiment with it.
I like it when Booty posts the questions about antenna ideas, makes one think outside the box

 

[Captain Kilowatt]

The lengths and spacings of the parasitic elements would not change. They are based on frequency of operation and not in relation to the size of the driven element. As for if a 5/8 would be better than a 1/2 wave, I think you are splitting hairs there especially because your supposd gains are based on manufacturer's CLAIMS and we all know how accurate they are.

 

[BOOTY MONSTER]

op:op:op:


How would the reflector and directors be made to work using an unbalanced driven element?

my idea here is only using the gainmaster antenna because it is said to be a center fed balanced element . but i have absolutely no problem with this discussion also considering typical end fed 5/8 s ...... but then comes the problem you just mentioned

The lengths and spacings of the parasitic elements would not change. They are based on frequency of operation and not in relation to the size of the driven element. As for if a 5/8 would be better than a 1/2 wave, I think you are splitting hairs there especially because your supposd gains are based on manufacturer's CLAIMS and we all know how accurate they are.

"The lengths and spacings of the parasitic elements would not change. They are based on frequency of operation and not in relation to the size of the driven element."
i did not know that . thanks
going with the big majority of folks claiming a half to a full s-unit of gain with their GMs compared to their previous 5/8 it seems there is truth to the gain claim this time , and they may even be conservative . or possibly everyones previous 5/8 before trying the GM was dammaged , improperly assembled , or had lost connections in its parts through weathering/time .

wavrider , some folks may wish you hadn't encouraged my wandering off beat questions , but thanks

 

[wavrider]

Booty you may be on to something there and Like the Captain said spacing between the reflector and director is a matter of frequency not size of elements.

The input impedance may change when the gainmaster gets within .25 wl of another element IE reflector or director, and then a yagi usually has around a 25 ohm input impedance and use a mathing network, gamma, beta or something similar to bring the impedance up to 50 ohm.

Now if you have a GM to play with, try putting a reflector behind it, the boom would need to be isolated from the driven element and most likely the reflector also.

It may be a fun experiment.

 

[Marconi]

Booty you may be on to something there and Like the Captain said spacing between the reflector and director is a matter of frequency not size of elements.

The input impedance may change when the gainmaster gets within .25 wl of another element IE reflector or director, and then a yagi usually has around a 25 ohm input impedance and use a mathing network, gamma, beta or something similar to bring the impedance up to 50 ohm.

Now if you have a GM to play with, try putting a reflector behind it, the boom would need to be isolated from the driven element and most likely the reflector also.

It may be a fun experiment.

WR, in my experience with the GM, its best function is far too sensitive to stuff around the antenna for it to work well in a beam type installation. Maybe BM was thinking of a center fed 5/8 wave radiator, like an extended double zepp (EDZ) being used as a driven element for a beam. Maybe in such a setup an EDZ might yield a little gain advantage over a similar 1/2 wave yagi...if it can be matched well.

IMO if this was so, we would already see such beams available.

Even if you installed a raised vertical GM in between two appropriately sized passive elements like a beam setup without a boom, I think the GM would perform poorly. This would be due to the director and reflector being so close. The GM's matching system and the choke does all the work, and if it's skewed by stuff very close by, no telling what might happen. IMO, it won't likely be very good.

 

[Marconi]

The lengths and spacings of the parasitic elements would not change. They are based on frequency of operation and not in relation to the size of the driven element. As for if a 5/8 would be better than a 1/2 wave, I think you are splitting hairs there especially because your supposd gains are based on manufacturer's CLAIMS and we all know how accurate they are.

I think CK is right. Remember that the AstroBeam antenna has a typical reflector and a director, while the radiator is only about 12' feet long or less. For years when that one was reported to work you hardly ever heard anyone say anything bad about its performance. So, as far as the physical radiator length question goes, I think the length can work both ways, long or short, it don't matter as long as it's resonant.

 

[wavrider]

Marconi you are correct, look at the folded dipole being usd as a driven element, it is shorter in physical length but the reflector and director are longer in physical length yet it works great as a yagi.

Yes the GM may be to sensitive, and I have read where it does like to have coupling effects when exposed to nearby metal structures so, it would probaly be a failed attempt, but booty would have had fun trying and that is what the hobby is all about having fun.

 

[Needle Bender]

Hah! I just found this on a Google search.
I see you were asking once before, Booty. I don't know how I originally missed this one.

 

[BOOTY MONSTER]

i must of been having too much fun the other day and forgot about this thread .
my apologies to anyone that may have been harmed by the second post