1.6 vswr on 2 , 20 and 40

[BOOTY MONSTER]

ive got my homebrew antena tuned to 1.6 across the cb band . its as low as it will go , its gets higher if i keep going . thats not terrible , but i was hoping for better . i think i know why and i just want some second opinions .

the feed point is only about 8 feet off the ground and the bottom of the sloped ground radials are about 1 foot off the ground . there is a rancher about 15 feet to one side of it and some 30ish feet tall trees about 10 feet away on the other side . one end also has about a 60 foot tree about 25 feet away . im thinking i cant tune any lower due to reflect from the house and trees and being so low . im also thinking that once i get it up in the air so the feedpoint is above the house at about 27 feet that it should go down some .

does that sound about right ? the verticle height is 22 1/5 feet .

http://www.worldwidedx.com/cb-antennas/36898-pics-progress-homebrew-5-8-a.html

 

[GLR]

nothing wrong with 1.6

 

[HiDef]

Have you tried changing the GP angle by moving in on the support to wire connection?

The earth is going to change things that close.

 

[Moleculo]

I think you're going to find that the SWR will change as you get it up in the air. Adjust it as close as you can then stop messing with it until you raise it up and see what it is.

 

[W5LZ]

Anything around that antenna is going to affect it's 'tune' to some extent. I have a feeling that the fence and trees, while having some affect, are not really that big'a deal at all. No specific suggestions, just 'fiddle' with the impedance matching to get it lower. That would hold no matter where the thing was situated, ground level, 40 feet 400 feet in the air. Whether it was a 5/8 w, 1/4 w, or some other fraction of a wave length, things around antennas affect it's resonance more than it's input impedance. Of course, that input impedance is going to be affected by resonance to some extent, just not as much. I just don't know of a good way to do all that figuring and 'fiddling' with just an SWR meter. Are you getting a sneaking suspicion where that's headed? Yeah, well, them things do make things much easier to 'play' with.
- 'Doc

 

[hookedon6]

about this time, some one will post about changing his coax length

 

[packrat]

Just get the most expensive coax you can find. That'll fix it.

PR

 

[BOOTY MONSTER]

well its gonna be raining here for the rest of the week so i wont be messing with it till next week . got some comments on another forum suggesting that i could try adjusting the verticles length so i might try that . im currently at 22 1/2 feet on the verticle so i might try 23 feet .

i got a new so-239 yesterday so ill mount that and have a cleaner feed line connection than just bare coax ends .
heres another question.......is the wire from the 239 on maco type antennas with a tuning ring a part of the radiating system , or rather is its length a factor in the tuning of the antenna ? the reason i ask is im undecided about using either a peice of coax with or without the shield going frrom the 239 to the ring . the shield wouldnt be connected to ground . also , is hot glue from the little guns RF conductive ?

ive been talking on the antenna yesterday and today and even sitting on the ground like it is my locals that i checked signal levels with on the 1/4wgp in the air are seeing increases on their s-meters . one about 7 miles away said i gained 2 1/2 to 3 units on him .
so thats a great example of just how inaccurate s-meters can be . LOL

 

[W5LZ]

Booty M.',
About that ring. If the center part of the coax connects to it, then it's part of that portion of the antenna, so yes, it radiates. It doesn't radiate much compared to the rest of the antenna, but that's because of it's relative size. So treat it as if it was a radiating part of the antenna.
What that 'ring' is, is an adjustable amount of inductance between the 'hot' and ground portion of the feed line which puts it in parallel with the feed line and in series with the antenna. It would be the same basic thing no matter what it's shape. It can be coiled up, a bent, folded, square, or circular shape, electrically it has the same characteristic, that being an inductance of the 'right' value to do the impedance matching between feed line and antenna. A straight section of conductor has so much inductance. If you change the shape of that straight section of conductor (coil it up, for instance), you can get the same amount of inductance in a smaller space/volume/whatever. And if you put that inductance in the right place, it will do the same 'matching' as some other 'shaped' inductor. That's absolutely normal (if you can call any of this stuff 'normal'?). It does the same job no matter if it's a coil, 'ring', 'trombone', or a 'hair-pin'.
The 'tricky' part is understanding why what looks like a 'short' to ground does this matching instead of just being a short. Which deals with how things act at different frequencies. It's frequency related just like antenna lengths are. (And I figure you already know that, but maybe someone else doesn't?)
It does radiate, but that radiation is incidental, it doesn't amount to anything significant.
- 'Doc


(My word descriptions are not as good as my crayola drawn pictures, so I hope that made enough sense to understand. If I ever figure out how to post pictures on forums, I'm going to use very pretty colors of crayolas! But not pink, that doesn't show up too good on a white background...RATS!)

 

[Moleculo]

about this time, some one will post about changing his coax length

LOL

is the wire from the 239 on maco type antennas with a tuning ring a part of the radiating system , or rather is its length a factor in the tuning of the antenna ? the reason i ask is im undecided about using either a peice of coax with or without the shield going frrom the 239 to the ring . the shield wouldnt be connected to ground . also , is hot glue from the little guns RF conductive ?

The tap from the SO-239 to the coil ends up being part of the matching system and it radiates some. The shield of the SO-239 goes to the radials. I wouldn't use coax for the tap, even if you don't connect the shield to anything. Ground strap works pretty good, but there are a few ways you can do it.

Hot glue conductive? No, it isn't unless you've got something special.

 

[BOOTY MONSTER]

thanks for the speedy replies guys . so just a single unshielded conductor is what ill use to tap the tuning ring fron the 239 . ive got some scrap 8x coax so ill just use a peice of that without the braid/shield so itll have a nice thick coating/jacket to protect it .

 

[wavrider]

Pic of old school inductor tapping to get impedance matched on 5/8 wave homebrew vertical.

By adjusting the tap and also adjusting the vertical length this antenna will really broadband.

good luck on the verticle.

Base of the inductor is at ground potential and the top of the inductor is attached to the radiating vertical element.

SCH 40 electrical conduit was used as insulator and the vert is insulated from the base with a smaller piece of pvc inside the sch 40,, works beautiful

inductor is 14 turns of 14# house hold electrical wire with 1 1/2 inch inside diameter. 10 inches long in length.


Note the choke coil, ugly balun, ( bottom right of mast next to boom)a must to stop the coax from radiating and truly get the antenna tuned no matter what length of coax is used after tuning the antenna it will stay tuned.
so-239 is atached to back plate of support and puts the shield at ground potential. I used normal stranded wire from the center fo the so-239 to the tap of the inductor.

This was an experiment using a 4 element beam on the horizontal side as the reflector/counterpoise elements. worked fantastic