smaller groundplane for higher feedpoint ??

[BOOTY MONSTER]

well , ive moved again . but this time im in a 2 story house in a pretty nice hood and the home owner has told me theres no HOA rules and gave his blessing on a CB antenna . !!!!!!

the side of the house id like to mount to looks to be about 35+ feet to the peak of the roof , but less than 40 feet . so ill be able to put my antennas feedpoint 15 feet or more heigher than befor and hit that first wavelength + above ground that ive so often read folks talking about . i dont think theres anything magical about being 36 feet vs. 30 or so , but im a definate believer that higher is better with the biggest thing being to have the feedpoint well above any nearby structures

anyhow . even though my PVC and wire ground plane was very effective (till a snow laden limb decided it wanted to lay on it) i need to have something more attractive or less noticable but still effective for a ground plane . there are a lot of big trees close to and around the house so that will keep my antenna from sticking out like a sore thumb , but id still like to draw as little attention to it as possible . the big white X always caught my eye

i have 2 ideas in mind ....
i had looked and asked about the boomer GPX befor but now im considering imax GPK . the mini saw horse bracket design looks to be a perfect way to mount to my 2x4 (which ill replace with a solid plastic lumber 2x4 or 2x6 since this will be more or less a permanent install) to keep the ground radials just below the feedpoint and still have the antenna isolated from the mast and earth ground . the elements are a 6 ft wire on fiberglass sticks , 2/3 the length of full 1/4WL elements . im also thinking the sloped F/G elements will make the install a lot easier than stiff horozontal tubing with all these trees around the place . the down side is i wont be able to brag about the whole antenna being homebrewed LOL .
heres a link to pics of the homebrew to show what ill be attaching to .

http://www.worldwidedx.com/cb-antennas/36898-pics-progress-homebrew-5-8-a.html
http://www.worldwidedx.com/home-brew-mods/38300-64-homebrew-temporally-finished-up-pics.html

from what ive been reading lately im getting the impression that with antennas bigger than 1/2WL (5/8 WL) that full size radials arnt as necessary and that the higher the bigger antenna is above ground also can reduce the need for full size ground elements .

my second idea is to use another X but this time either use black pvc or paint the wite pvc with a few coats of black paint . i think black would be much less noticable with the trees around the antenna . im also thinking ill use black tv coax for its coloring and to have more surface area on the elements by using the shield part . and im thinking to make the whole thing smaller . instead of using four 5 ft pvc sections for the X and four 9 ft 12 gauge wires .... to this time use the tv coax as described above but make them 48 or 52 or 60 inches long and the X standoff would be four 2 1/2 ft peices of pvc . ill make this stronger than the inital one . this would be much cheaper than buying and shipping a kit and also allows me to keep the whole antenna homebrewed .

heres a link to a calculator i use for figguring ground element angles .
Right-Angled Triangle Calculator

i know 1/4WGP's need about a 35 degree angle to tune to 50 ohms and that bigger antennas with matching networks/tuning coils dont need a certian angle to tune . i am wondering though if a 23 degree angle (as shown on the hypotenuse/C of the triangle calculator) is too steep if i used four 24 inch standoffs (B) and 60 inch elements (C) .


im very intrested in comments on shorter ground elements on bigger antennas and how much slope is too much for ground elements . and of course comments on the imax GP kit .

thanks

P.S. i do not want to and am not going to use the mast as a ground element like the antrons , imaxs and ringos do .

 

[555]

2 story house
why not get a tripod or roof mount and go alittle higher and be in 2nd wavelength

 

[Robb]

The IMAX GPK radials are only 6 ft in length. Don't you need 1/4 wave length/9 ft ground planes for your home-brew 5/8 wave?

I had an idea that I could use four 1/4 wave length guy wires as ground planes; then hook up Dacron rope to the ends of these wires. In this way, they could act like ground planes AND be a part of the guying system. So long as the downward angles are consistent, it should work.
Just a thought...

 

[Simon004]

I've also homebrewed a 5/8ths wave, and I went out of my way to make the radials a 1/4 wave long. A guy whom I respect, and who knows his antenna theory, suggested to me that 8 1/8 wave radials (like on the sirio 827) actually work better, and will give a lower angle of radiation from the antenna than 4 1/4 wave radials would do. I'm going to try this, but I haven't done yet, so I have no idea or evidence if it is true or not. Would be interesting if anybody could model this or just comment on their experience. I think 8 1/4 wave radials would be even better, wouldn't it?

The angle of the radials has little effect on the radiation angle of the antenna, but more with the impedance, so if you change the angle of the radials, you would have to adjust the tap point on the coil or change the overall length to retune the antenna.

 

[BOOTY MONSTER]

im not interested in going higher than several feet above the roof line and i dont want to guy wire it . i also dont want to do a tripod on the roof . i want to do as little dammage/attaching as possible to the house and i absolutely dont want to be fastening to the actual roof deck/top . im going to run a mast from the ground up and and use a simple but sturdy bracket on the rake at the peak of the roof with a heavy dose of silicone in and around the lag bolts to be absolutely sure no moistures enters around it .

i do appreciate the suggestions , but ive already figgured out how i want to mount it . and since i was very satisified with the antennas performance at 24-25 feet to the feedpoint im sure ill be happy with it at 35-40 feet .

simon , eight 54 inch ground elements is something i can consider . i may just do four sloped 9 footers again . lowes has black rg6 tv coax for 24 cents a foot and i can sand and paint the the 1 inch pvc stand offs with several coats of flat black krylon spray paint to so they're less noticable . ive got a few tricks in mind to make it stronger and cleaner looking . if i go the homebrew route again , which im leaning twoards . i just want to get some others opinions on the ground elements .

 

[Marconi]

I've also homebrewed a 5/8ths wave, and I went out of my way to make the radials a 1/4 wave long. A guy whom I respect, and who knows his antenna theory, suggested to me that 8 1/8 wave radials (like on the sirio 827) actually work better, and will give a lower angle of radiation from the antenna than 4 1/4 wave radials would do. I'm going to try this, but I haven't done yet, so I have no idea or evidence if it is true or not. Would be interesting if anybody could model this or just comment on their experience. I think 8 1/4 wave radials would be even better, wouldn't it?

The angle of the radials has little effect on the radiation angle of the antenna, but more with the impedance, so if you change the angle of the radials, you would have to adjust the tap point on the coil or change the overall length to retune the antenna.

Based on my current thinking, I agree with Simon's buddy to a point. I'm not sure about the effects on angle of radiation business, because I can't see or test the angle. However my previous testing did suggest that adding more radials did improve the TX/RX signals on my 1/4 wave radiator Marconi6x, where I compared 1, 2, 3, and 6, 1/4 wave radials.

I cannot model and not much modeling is done with CB stuff. If proper modeling does what it is supposed to do, then it would be great to be able to understand the application.

I have been studying the following work on radials by W5ALT. I just posted his article "W5ALT Antenna Radial Notes" to my album in my profile with comments. http://www.worldwidedx.com/members/marconi-albums.html

Edit: Sorry guys, but all the comments I added to my images in the albums noted above were erased somehow. This is the second time this has happened after I spent time adding comments. I don't believe this is someone deleting stuff however. I think the album section has some critical flaws in its creation and edit processes.

Sometimes I find it easy to create duplicate albums without realizing it and at other times the order of images added---ends up posted in some random order in the index. This is only important when a series of images has some order to it---like page numbers or dates. There is something strange in using the edit pictures and edit albums that I have not detected in using the feature. Unpredictable things just seem to happen.

Maybe Moleculo or Robb could check this out and let me know what I'm doing wrong.

It is a study of 2 meter verticals, but maybe some understanding can still be gained by studying this work. I also posted earlier the work on 10 meter 1/4, 1/2, 5/8 wave verticals by nm5k. At this point I believe the work of W5ALT is far more objective and detailed. nm5k may be showing a bit of bias in his report and he is using the demo version of Eznec and it is limited by the number of segments that can be used. Plus Mark uses a different number of segments in almost every one of his 7 models. If the limit of segments can be of a concern in accuracy then using a different number of segments between models to be compared can also be a concern.

This said, I'm still skeptical as to modeling results I see on the Internet and for sure if two results don't seem to jive.

BM, you have a large file of references. Could you check and see if you can find some other comprehensive modeling studies, preferably 10-11 meters, and link them or send them to me?

BTW, will your new installation be installed where you can make simple changes to the ground plane? It is too bad that nm5k's reports on the 5/8 wave modeling did not include the mast in all of his models. The 5/8 radiators that did show the mast indicated there was a little current flowing on the mast, but not nearly as much as on the radials. Too bad he didn't show the actual current distribution values. Will it be possible for you to test the insulation idea in your new setup? About your height, I think you might see some increased signals if you could get the radials at least a 1/4 wavelength away from the roof. I know how it is to have limitations, but the most significant thing I noticed last summer with my work was how much attenuation there was to the signals while being close to my house with the bottom of the antennas. If you weren't checking that affect out closely you could miss it completely.

 

[W5LZ]

Here are a couple of general things that are a fact generally.

The angle of the radials have more affect on the antenna's input impedance than the antenna's angle of radiation.
The antenna's height above -effective- ground has more affect on the antenna's radiation angle than on it's input impedance.

There are "if's" and "but's" to both of those thingys, but that's how they generally affect things.

The number of radials used just depend on where they are, in 'dirt', or in the air. I can't give you a cite for that, but it's not anything new by any means. It takes more radials in 'dirt' than it takes for the same results if those radials are above ground in the air. That 'above ground' means more than just several inches/feet, it's measured just like other antenna stuff, in wave lengths or fractions of wave lengths, and varies with the frequency of use. (One reason why testing things at VHF can tell you things about HF, and 'scaling'.)

None of this is ever going to be absolutely 'true' for every set of circumstances. What may work just dandy at my antenna site may not work in yours without some 'finagling'. That's about as common as it gets.
- 'Doc

And if it wasn't for all that 'finagling', none of this would be any fun. Would it?

 

[Marconi]

I fixed my comments to the album noted above:

http://www.worldwidedx.com/members/marconi-albums-w5alt-antenna-radial-notes.html

BM, please check your files for more modeling work like W5ALT did with 2 meters.

 

[BOOTY MONSTER]

thanks for the replies guys . and marconi i really enjoyed our conversation the other day , thank you for Elmering me on the phone .

i cant seem to find the places i found the coments about using shorter radials the higher a verticle is above ground . i dont save links like i used to because it kinda got out of hand . LOL . i stumble onto a lot of stuff googling/researching other stuff trying to get a better understanding of things concerning the hobby , some of it seems accurate , some of it not at all based in truth and quite often to far above my head to make heads or tails of it . ill try to save the links if i run across them again , but im just gonna stick with full 1/4wave ground elements .

i wanted yalls opinion about the shorter ground elements though because you can find almost anything on the WWW , but theres several folks on this forum that ive found invaluable when it comes to filtering out the bull crap and pointing me in the right directions .

i did save a few links on ground elements info that ill post just incase someone else may be interested .

the downloads in this link may be what i was looking at befor ..... but my free version of adobe wont open it even with todays latest update ...
Antennas By N6LF: Design of radial ground systems

heres some others ...
http://forums.qrz.com/showthread.php?t=224105
http://forums.qrz.com/showthread.php?t=217687
Counterpoise?
The Mystery of radials
Basics of antennas

so ive decided to just stick with 9 ft 1/4 wavelength ground elements .
now............
ive found a place locally where i can get either 1/4 inch aluminium rod or 1/8 inch stainless steel rod in 12 ft lengths for $4 - $5 bucks each . i have to make a minium purchase of $30 though . ive also got an idea in my head on how i could use the bottom of a big thick old aluminium frying pan or pot to attach the ground elements too . if i make a H type cut in the middle of it about 3 3/4 inches wide and about 2 inches on each side and fold them up it should fit over the 2x4 and the the bent up flanges would be perfect for running bolts through to attach it to the 2x4 and using those same bolts to attach to the ground side of the antenna .

im gonna stick with sloped radials . from what i under stand it makes the over all antenna longer/taller and may give some slight benefit on the recieve end . it will also make the antenna easier to deal with on the ground during tuning and inital testing to be sure its assembled strongly and working properly , and also while raising it . ........ and of course since i have to make a minium $30 purchase im also considering 6 or 8 elements .

i wont be needing my X under the wire radials . im am interested in opinions on on the wire ground elements moving in the wind . and also opinions on weather to use the 1/4 inch aluminium (much stiffer) vs. 1/8 inch stainless steel (much more flexable) . im thinking the 1/4 inch aluminium for the larger diameter and less movement in stronger winds . ive seem some ham antennas with wire ground elements (horozntal but slightly bending/drooping down) so im thinking a lil wiggling isnt a big issue ????? im also thinking/hoping that using 6 or 8 of them will minimize/trivialize any negative effects of them moving in the wind a bit .

and of course itll be isolated from the mast and earth ground and have a coax choke about 9 feet below the feedpoint .

thanks again for all your comments folks