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A Dipole for your CB Base Station?

A 1/2 wave dipole does have some gain over a typical 1/4 wave vertical, but nothing like 5 or 6 dB's worth. It doesn't matter if it's hunk horizontally or vertically, it's still 'some' gain not a lot. Of course, that depends on the type of vertical doesn't it.
As for a full wave length dipole, there's no particular benefit to it. The radiation get's really 'odd', that pattern isn't 'linear', it starts to get cut up into lobes and nulls quickly.
Now if you want to make that full wave length 'dipole' into a loop, that can certainly be a different story.
- 'Doc
 
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I stretched my wire out for a 1/2 wave and cut it in two 110" sections (11m) and strung out my ladder wire. I have about a 35' run of 300 ohm ladder wire to the top of my roof. I tucked all the wiring under the lip of the shingles covering the hips. The antenna splits the roof and the ladderline runs the center hip perpendicular to the legs of the dipole. I fabbed up a balun/choke out of used coax-17' wrapped around a 2" piece of PVC with eye bolts for the ladder line and a 239 connector to jump back to my radio. I placed this near the eave of my roofline by my 1/2 car garage/workshop. At the antenna end of the ladderline I put 6 wraps the size of my fist into the line and tie wrapped it tight.

After 4 trips up trying to tune this thing I ended up with 102" x 2, 204" total, of antenna and a SWR of channel 1, 19, 40; 3:1, 1.5:1, 5:1.

Any tips on tuning this setup without making another 4 trips up a ladder and up a stupid high pitched roof? I basically spent some google time and found several setups like this that worked for other people. Mine isn't what I'd like it to be.
 
Brown van brought me exactly 35' of some 400 and 4 connectors today for another project. He's like a genie. I'll give it a whirl on the dipole tomorrow before I scrap the rooftop project.
 
pipe layer said:
Did anyone mention the horizontal dipole has 5 to 6 db gain over a vertical over real ground?
Click to expand...

Hey pipe layer, I have read some reports about this advantage for horizontal antennas from some of the big names in radio antennas, but I don't think most in this forum bunch have really considered what is truly being said and meant in those reports.

In my real world experiences I see the obvious differences in polarity and the difference is big and noticeable, but I never considered there was this big of a gain difference either, so I understand these guys point when they say it isn't true.

However, I still think the claim you and others are making in this regard is technically correct, because I see the same thing happen with my models, and I would believe modeling over some writing on a "truck stop restroom wall" any day. <gotproof>
 
Full wave?

W5LZ said:
A dipole is a pretty versatile antenna. It can be hung vertically, horizontally, and almost anything in between those two. Bent in to various shapes to fit the area you have to put it into. If it's high enough not to 'clothes-line' yourself, it'll probably work. If you can put it on top of a huge pole/mast/tower/tree, it'll probably work even better. A dipole (most common meaning being a center fed 1/2 wave antenna) is probably the most 'universal' antenna in use. They are not difficult to make, but do require 'tuning' unless you are just ridiculously lucky. That just means adjusting the length, basically.
For HF dipoles, a balun just isn't all that necessary. Won't hurt, but in most cases also won't help either. Dipoles are also the 'standard' all other antennas are compared to. Several 'qualifications' to that, but still a 'standard' means of comparison.
What you make a dipole out of depends a lot on what you happen to have on hand. The size of wire doesn't play any significant part other than to be strong enough to hold it's self up in the air with out stretching much. Anything smallet than about a 18 guage is sort of 'too small', concerns the mechanical 'strength' thingy, not electrical characteristics. Larger doesn't hurt, it just gets sort of unwieldy(?) at some point. Size of wire doesn't determine how much RF power it's capable of handling.
The 'magic' number for a 1/2 wave antenna is '468'. Divide that by the freq in Mhz and you get feet. Adding a foot or two extra to make connections with is sort of a good idea. You'll have to tune it anyway, so any left over unused length gets done away with, no big deal.
Dipoles are only difficult to make until you make the first one. Then, you have at least some idea of what's required, and the following ones are easier. Keeping both 'sides' of that dipole the same length is a very good idea. If you trim so much off of one side, trim the same amount off of the other side, or add to it the same amount.
DO IT! Do it! (They're cheap too!)
- 'Doc


Quick-n-dirty!

10 foot extension cord.
Cut the receptical end off.
Separate the two wires down to the plug end.
Solder coax center conductor to one 'blade', the braid to the other 'blade'.
Adjust length of each side the same amount till it works 'right'.
Quit.
That's about as 'dirty' as you can get. It'll work just fine.
Click to expand...

What about a full wave 11 meter vertical dipole with one end attached to a nonconductive outrigger off of the antenna mast of my tower. The outrigger would be used as a standoff. The top of my tower,mast and all is 37'.
 
There's no particular benefit for using a full wave vertical antenna as far as I know. For vertical antennas, once you get to something like 5/8 wave length the radiation pattern really get's 'odd', breaks into numerous 'nodes'/'nulls', not much 'low angle' stuff. Matching impedances (SWR) also get's sort of difficult, the impedance of an end fed full wave antenna is nowhere near 50 ohms. Certainly not impossible to match, but not exactly easy/normal.
How about mounting the thing on the side of a tower? That's not impossible either, but it does have complications in that the radiation pattern will certainly be affected, changes in 'shape'. There tends to be a 'null' in the direction of the tower. If that suits your purposes then that's good. If not, then it's not so good. If the idea is to experiment, see what happens, knock your self out! If it's to gain some advantage, that's really 'iffy', just depends on what the disadvantage is you are trying to get rid of.
- 'Doc
 
W5LZ said:
There's no particular benefit for using a full wave vertical antenna as far as I know. For vertical antennas, once you get to something like 5/8 wave length the radiation pattern really get's 'odd', breaks into numerous 'nodes'/'nulls', not much 'low angle' stuff. Matching impedances (SWR) also get's sort of difficult, the impedance of an end fed full wave antenna is nowhere near 50 ohms. Certainly not impossible to match, but not exactly easy/normal.
How about mounting the thing on the side of a tower? That's not impossible either, but it does have complications in that the radiation pattern will certainly be affected, changes in 'shape'. There tends to be a 'null' in the direction of the tower. If that suits your purposes then that's good. If not, then it's not so good. If the idea is to experiment, see what happens, knock your self out! If it's to gain some advantage, that's really 'iffy', just depends on what the disadvantage is you are trying to get rid of.
- 'Doc
Click to expand...

Thanks. I was thinking along the same lines. I guess I was thinking about a full wave dipole to see if one would have comparable performance to store bought 5/8 wave ready made verticals ie:IMAX 2000,Gain Master,Maco V58
 
Just for your information...
A dipole is commonly thought of as a 1/2 wave antenna fed in the center. If it's not a 1/2 wave length long, but still fed in the center, call it a doublet instead of a dipole. Just a difference in terminology, but it can sure clear up mistakes in what you are talking about.
There's no significant difference between the radiation pattern of a vertical dipole and an end fed 1/2 wave vertical antenna. The biggest differences between the two would be in how the input impedance is handled. That end fed 1/2 wave will have a very high impedance and is why the 'A99' uses a matching device at the input. That matching device is probably the biggest draw-back to them, it does have limited power handling ability. If the thing was center fed with no matching device used, that power handling ability would be much greater. That's not done all that often because mounting a center fed antenna isn't exactly as easy as an end fed one. Oh well...
The only significant difference between a 1/4 wave, 1/2 wave, or 5/8 wave vertical is in the shape of it's radiation pattern. None of them 'radiates' any more power than is fed to them, they just 'put' that power in different places. The total amount is still the same.
- 'Doc
 
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Lil'Yeshua said:
Half of 11 meters for the positive element and vice versa for the negative.
Click to expand...

make a quick one and try it out, havent heard of anyone doing that,, and usually there is a reason. but thats all part of the fun , trying something. its only a dipole if it doesnt work you can always cut it down to the standard dipole length. if it wasnt 4*f outside here id go try it just for something to do
 

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