2 in one antenna idea .... ?????

[BOOTY MONSTER]

ok , this may sound weird , and i may have read too many TOA comments .. LOL

i'm thinking of making a gamma and attaching it about 9 feetish below the tip of my vector and running a piece of 8x up to it . i want to try to be able to use the same antenna but be able to switch between the low TOA of the vector and the higher TOA of the vertical dipole . to be able to change to the lobe that allows me to tx/rx the best with individual stations , if one WL actually has a advantage over the other ATM of the contact .

the challenge , i think , will be to both have the dipole tune with the bottom element being over a full wavelength long (including the mast) and also not have it noticeably negatively effect the tuning and performance of the vector . i'll need to get another section of coax and a switch box . i'm also wondering if the coax running beside most of the vertical of the vector will mess up it's performance/tuning .. ??


anyhow ..... any idea if it has a snowballs chance in hell of working ?? LOL

 

[Robb]

I did like your idea to build your own copy of a Sirio Gain Master - though . . . .

 

[High Voltage Mobile NJ]

i would just spend more money and do it right . rgx coax is only rated for 500 watts bird . get your self an air variable 3-30 pica or 3-80 pica. your antenna will now handle more power , sound clearer , and you just lowered your angle of radiation slighty . do it right , dont waste your time on making baulms that are only good for low power situations and are not the proper way to tune your antenna system beacuse it makes weak spots and generates another crosstalk frequency harmonic . you are not suppose to wrap coax period .

 

[High Voltage Mobile NJ]

ok , this may sound weird , and i may have read too many TOA comments .. LOL

i'm thinking of making a gamma and attaching it about 9 feetish below the tip of my vector and running a piece of 8x up to it . i want to try to be able to use the same antenna but be able to switch between the low TOA of the vector and the higher TOA of the vertical dipole . to be able to change to the lobe that allows me to tx/rx the best with individual stations , if one WL actually has a advantage over the other ATM of the contact .

the challenge , i think , will be to both have the dipole tune with the bottom element being over a full wavelength long (including the mast) and also not have it noticeably negatively effect the tuning and performance of the vector . i'll need to get another section of coax and a switch box . i'm also wondering if the coax running beside most of the vertical of the vector will mess up it's performance/tuning .. ??


anyhow ..... any idea if it has a snowballs chance in hell of working ?? LOL

keep in mind the vector has alot of radiation from the bottom side to . so if you want more radiation focal point on the tip of ya antenna , i would not go that way with the coax . take a flouracent bulb and see how much rf you get , its easy enough to change out and go another way .

 

[wavrider]

i you are not suppose to wrap coax period .

Since when?

 

[wavrider]

i dont waste your time on making baulms that are only good for low power situations and are not the proper way to tune your antenna system beacuse it makes weak spots and generates another crosstalk frequency harmonic

Do you mean baluns? They do all that?

 

[W5LZ]

It sounds like what would be happening is just a method of changning the impedance match of the antenna for use on two bands. It wouldn't change the antenna's resonance at all, just how it's being fed.
Would it work? Probably, but that antenna would then not be a good performer on either band. That second feed line/feed point would certainly change it's radiation characteristics, and compromise it's "tune" on either band, I would think.
Try it, see what happens!
- 'Doc

(O.D.'ing on TOA isn't super serious, not deadly, but can produce hallucinations, be misleading. Is there a 'TOA Anonymous' near you?)

 

[BOOTY MONSTER]

i would just spend more money and do it right . rgx coax is only rated for 500 watts bird . get your self an air variable 3-30 pica or 3-80 pica. your antenna will now handle more power , sound clearer , and you just lowered your angle of radiation slighty . do it right , dont waste your time on making baulms that are only good for low power situations and are not the proper way to tune your antenna system beacuse it makes weak spots and generates another crosstalk frequency harmonic . you are not suppose to wrap coax period .

i only use 200 pep , so 8x will more than handle my power requirements .i dont understand how the air variable would make my signal sound cleaner or how it would lower my TOA , can you explain how that works please ? no baluns will be needed or used , air core coax chokes will be used though .
why is coax not supposed to be wrapped ?

the vector is supposed to have a low TOA so i'm won't be trying to get a lower TOA , i want the option of a higher TOA to play around with while keeping the same tip height . i don't expect it to be the bees knees .... just something to play with . my hope is ... that i can get my dipole idea at the top to tune low enough to use , and i'm sure the vector will need to be re-tuned , i may have to play with the length of the vertical a bit too to if it sees the gamma as adding length .
just something to play with .... and thinking out loud about it fishing for tips and comments .

 

[BOOTY MONSTER]

It sounds like what would be happening is just a method of changning the impedance match of the antenna for use on two bands. It wouldn't change the antenna's resonance at all, just how it's being fed.
Would it work? Probably, but that antenna would then not be a good performer on either band. That second feed line/feed point would certainly change it's radiation characteristics, and compromise it's "tune" on either band, I would think.
Try it, see what happens!
- 'Doc

(O.D.'ing on TOA isn't super serious, not deadly, but can produce hallucinations, be misleading. Is there a 'TOA Anonymous' near you?)

hey doc , it's still gonna be a mono-band CB antenna . there will still be coax going to the V's feed-point/gamma and a second run up to the gamma with a coax switch in the house to choose between the two . heres a rough/crappy idea of what i have in mind ... the white line below the top is the gamma to use it as a 1/4wgp and the black line is coax going down . i was thinking about the second feed-line effecting the vector , i think i may have a idea on how to run the coax inside the vertical from the 1/4's FP down without making a hole in the side of the aluminum

having the ground side of the dipole element at 39 ft is going to be the thing to overcome though . maybe dropping the antenna 3 ft so it's 36 ft may help with tuning though . or it may just be a waste of time , but still a entertaining lesson for me .

 

[wavrider]

Booty, I had to reread your post a few times to grasp what you are thinking about. I think I got it, ( a lot of thinking here)


The idea is worth while but I do not think it will perform as you may want it to.

The full vertical radiator for the vector is what you will be tuning with the gamma way up there in the air. The current will still go the full length of that radiator as there is no isolation to make it a 1/4 wl antenna so IMO (and I am probably wrong as I often am) I do not think it will perform as a 1/4 wl gp.

That is just my guess as I have never tried that type of feed configuration, nor have I seen one like it.

It may work great. Maybe CK will chime in with his thoughts on it but heck of an idea for a dual feed single radiator antenna.

 

[BOOTY MONSTER]

i'm sure you're right . it'll be a compromise , and compromises never give both sides exactly what they want . it'll be something to play with .

 

[wavrider]

Always fun to play with that is sure and it may do just what you want it to do. Let us know how it turns out.

 

[W5LZ]

It all depends on how long that vertical element is. If it's a half wave, then feeding it at one end, or in the center isn't going to make much, if any difference, it's still the same half wave radiator so the radiation pattern would be the same.
If you make the feed point of that gamma match at the 1/4 wave point, it's still going to be a 1/2 wave antenna, same end result. If you could 'open' that 1/4 wave point (cut off the top part), then you'd have a 1/4 wave from there down. But then you'd have really messed up the impedance matching that the 'basket' provides for the antenna. (Sort of a can't get there from here kind'a deal, you know?)
Now, if you were to start thinking in terms of a vertical array. Several (at least two) antennas stacked on top of each other connected by a phasing network, you'd end up with a very 'flat' radiation pattern. If you opened up one of those phasing thingys between elements, there would only be one element and the radiation pattern wouldn't be as 'flat'. But at HF, you'd be talking about something in the neighborhood of 40 feet tall. Not exactly a typical backyard antenna? (If you scale that down a lot, you'd be seeing the more typical vertical arrays used with VHF/UHF antennas.)
It isn't super impossible to change the length of an antenna, relays, what-nots. Changing the impedance matching for that longer/shorter antenna can get hairy real quick.
- 'Doc

 

[BOOTY MONSTER]

in a phased array are both antenna active at the same time ? i'd only use one at a time . anyhow , it'll be a entertaining way to waste some time and i can always just go back to the vector

 

[W5LZ]

Are all the 'elements' in a vertical array active at the same time? Yes, and they are in-phase, meaning same signal and polarity in each element at the same time. Because the polarity is the same, and like polarities repel each other, they result in a sort of 'flattening' affect on the signal produced by that array. Like mashing two balloons together, they 'pooch out' sideways. If you vary the phasing/timing then that 'pooching out' get's lop-sided and the radiation pattern get's sort of directional (varies the radiation angle, I think). If those phased arrays were arranged horizontally, two or more verticals phased together, then the radiation pattern get's directional in direction (not sure that made sense, did it?).
- 'Doc