11 METER CB ANTENNAS
I get asked quite often where to start with a home made station antennas.
I have a few opinions regarding antennas. To start with, I believe that antennas that you build will give you as much performance, entertainment and satisfaction as the large expensive antennas. I know that many of you just don’t want the hassles involved with making your own. The simple understanding you gain from making a few, will help you to know what to “buy” when that time comes. I believe that all forms of the radio hobby were meant to be fun and inexpensive. An antenna should be able to be made out of leftover wire, or tent poles from a yard sale or whatever you have at hand.
So with that in mind, lets see what we can come up with.
The simplest of all the antennas is the Dipole. It’s two pieces of wire at the end of your coax or feed line. Sounds easy huh? That’s because it is! They are used in all forms of communication radio from a music station in town, the Hams and best of all, you the CB Operator! These do really work!
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Remember that some trimming might be required. If your SWR (Standing Wave Ratio) is high on CH40 and low on CH1 you may need to trim it a little. Sometimes 101" on each side is closer to the sweet spot. If your match is high on Ch 1 and Low on CH40 your wire isn't long enough. When building your dipole, leave some extra to start with twisted into the loops at the ends.
There are several schools of thought about wire antennas. Big wire, small wire, solid wire, stranded wire, copper wire or steel wire there are a bunch of choices. The fact is.... they all work. We are lucky in the CB Band that with such low power radios, the wires are forgiving.
Some things for you to consider are where and how high to place your antenna. Wind loading might require you to use a heavy wire that won't stretch from the weight of the coax or bending of a tree. There are several ways to mount a dipole. Below are a few suggestions you will hear people talking about on the air. Remember the fun part is the experimenting to find what works best for you and your conditions! Remember 99% of the time the higher your antenna the better.
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Here are a couple of pictures I took this morning showing my current Home Brew base antenna. I bought 4 mobile stick antennas for $20 and used two of them plus a structural T tie bracket (reformed with a hammer while in my vise), mobile mount stud for the hot leg, 3/8-24 bolt through male to male adapter from a spring mount for the ground leg. I get 1:1 SWR on CH 20 with 1.3 in CH 40 and 1.4 on CH 1.
I may just beef up the bracket a bit (install a spacer between the tips of the "U"), plastic dip coat it and put it on the chimney.
The 1/4 Wave GROUND PLANE
Another antenna that is very simple to make out of spare parts is the 1/4 Wave Ground Plane. These are just about as easy as the Dipole to create. This does require some nuts and bolts and scrap metal. Depending on how you make it you may need a block of Plexiglass or wood or ? to use as your center insulator. A metal center mount would short out the radiator and the mast. You can use an old mobile metal antenna bracket but it uses a nylon insulator between the ground and whip. Click on the picture below for some Ideas on how to build yours.
CLICK FOR A LARGER VIEWOne Mountain Thunder Radio Group Member Takes It Further!
Before I get into details I'll tell you that I typically do this stuff completely by the seat of my pants meaning... usually not done properly or not done "the right way" and, usually done in an ugly, temporary fashion. That's why I always refer to my antennas as "white trash"! hahahaha
Delta's and loops in general are something I've only just begun to experiment with. They're so counter-intuitive to what I think an antenna needs to be. For example: How do you check the connection for shorts when its just one big closed circuit?!
Anyway, first I decided to use 27.5MHZ for the operating freq since I am a ham and use the 10 meter band also.
This site has a nice calculator: http://mysite.verizon.net/ka1fsb/loopcalc.html so I used that to calculate the length of the wire & came up with roughly 36.5 feet.
So I basically just cut a piece of wire to that length. I just used standard 14 Gauge solid copper wire from Home Depot. Then just soldered one end of the wire to the coax center conductor, and one end of the wire to the braid. Then I estimated where the apex would be, got on the roof and used a Velcro strap to hold up the top end to the mast. Once that was in place I stapled the far end to the corner of my eaves and just hung the other end from my gutter at the opposite eave.
I'm using Belden 9913 coax. Per recommendations I've seen on numerous sites, I coiled up 3 turns of coax about 1 foot in diameter right after the feed point which is supposed to help keep RF from coming back in to the shack. I've also read that this antenna doesn't need a balun as long as you have a good tuner, but I'd like to try my hand at building a balun next - never tried before. I do use an MFJ tuner which works well with this.
Needless to say I'm very impressed with the performance of this antenna. When it comes to 10-11 meters, most of the time it out-performs (stronger signal & less noise) my vertical and my wire dipole also cut for 27.5mhz.
I found some other sites that described this version of the antenna a lot better but I can't remember the url's for those. I've seen some diagrams that show there is some reflectivity with this particular style of delta. Right now the wire lines up in a North / South direction. And since the feed point is on the bottom corner of the loop, it should be vertically polarized favoring a northern direction (i think)!
This is all just fun for me and i don't take it too seriously, but I'd love to hear any suggestions you have. I typically just use what i have available - meaning the eaves of my house etc.
After I made the drawing... i realized how many different factors in the design I just don't even think about any more because they're 2nd nature.
Talk to you later everyone. If you're still reading at this point.. you're crazy! :)
Another Loop Antenna
This is a link to "Ghost Rider's" 10 / 11 Meter Loop Antenna
Ahhhh... A homebrew thing of beauty!
Send your Home Brew Antennas In to the new Antenna Category at The Mountain Thunder Radio Group!