.64 antenne plans wanted

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.64 antenne plans wanted

john
   cb   27 mhz or 11 meter  .64 antenna plans wanted
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Re: .64 antenne plans wanted

Possumn
Basically it's approximately a 22 to 23 foot vertical radiator of some kind of conductor with at least four 103.5" lower radials around it. If the lower radials are set 90 degrees from the vertical, the impedance of the design is near 30 ohms impedance so a gamma match is  needed to make it near the 50 ohms impedance of the coax, and the 50 ohms impedance that the radio is looking for. But if the lower radials are sloped downwards at a 45 degree angle as in some other antennas you've likely seen, the antenna is now made closer to the 50 ohms impedance range and a gamma match is not needed. The rest of the design is a squared off "C shaped mounting bracket about 1 1/2 feet tall, there is a hole in the top arm with a plastic insulator sleeve to keep the vertical radiator from touching the bracket, ground or lower radial section. and another plastic insulator is at the bottom arm to support and insulate the vertical tube section from the bracket and lower radials the same way. A short wire is usually hidden inside or next to this lower plastic "holder" for electrically connecting the vertical metal tubing that connects it to the center pin of the SO259 connector. And the lower radials are mounted or clamped in some way to the top arm of the bracket with out an insulator. This allows the shield portion of your coax to connect to the bracket and the lower radiators and only the center of the coax connects to the vertical radiator part. If you take a multi-meter and set it to the ohms setting, you will have no connection between the vertical and the bracket if there is no gamma match, or there will be a connection if you do have the gamma match. but again, sloping the lower radials downwards at a 45 degree angle eliminates the need for the gamma match that 90 degree designs require. ideally you can have as many as 64 lower radials but I'd just use 8 or less, but do use at least four. The bracket also has two u bolts to let you clamp it to a metal mast. The mast can be grounded or not, but You might think on adding a lightening arrester. I would suggest you do add what is called a "current balun" to keep any stray RF off your coax as well so it does not go back to your radio if your SWR is off.  it's just 5 turns of coax taped or fastened side by side around a 4 1/2" form of some kind, (which is not metal). You can use a metal form "like a 4 1/2 inch can" to wind this coil, but take it out and discard it once you've taped or wire tied the coil neatly in a row together.  Don't overlap it or cross it. It's hangs just below your antenna and your coax connects to it or it can just be some extra coax if your have enough to make up one.  The vertical radiator is often made of telescoping tubes like EMT conduit of different sizes so you can raise or lower them a bit to fine tune the SWR as low as possible. And they are locked together by a screw or clamps once the SWR is set.  The lower radials can also be EMT conduit as well. But you can also use wire (bare or insulated) to make the whole antenna out of and use a long nonconducting material of some kind to support it or hang it from a tree if you wish. Or you can use EMT conduit for the vertical part and wire for the lower radials if you wish and add an insulator of some kind to the ends of the 103.5" wire so you can change to guy ropes from there to the ground and keep the slope right as well as support the antenna. As long as the lower radials are electrically connected to the mounting bracket part which connects to the coax shield.  Larger materials like copper pipe or EMT conduits just last longer and can handle more power easily. I would not suggest you use wood for the mounting bracket as water would make it conduct electricity, But you can use your imagination on the design you wish to make with what you have available. The mount can be as simple as a piece of PVC pipe with the vertical fastened with in it clamped to a post, and the lower radials can be mounted on a separate plate near it as long as you can fasten the coax to both parts in some way. There's plenty of antenna designs on the web with lots of complicated calculations for designing them for use on any frequency you wish, I'd suggest you check out the ARRL webpage for loads of information. But this is about making a .64 wave CB antenna. The 5/8th wave uses a 21 foot tall vertical, the 1/2 wave uses a 17.2 foot vertical. And a 1/4 wave CB uses a 8.6 foot vertical. and pretty much in all of them you make it a bit too long and then adjust the SWR from there until it's as close to 1:1 as possible. I hope this helps. By the way, I have made a 3/4 ground plane similar to these dimensions, which is 27 feet tall, And it does have a current balun coil and the SWR is tuned to 1:1 across the entire CB band, but the angle of radiation transmitted by it is too high for any kind of local use. Shorter antennas transmit closer to a ground hugging angle, Mine's great for shortwave listening and may work well on some skip. But I can also easily change the vertical radiator part of it and it becomes a 1/4 wave CB antenna for local use which also has the same current balun coil and is also tuned in length to a 1:1 SWR on the CB band. (So who says you can't make different vertical lengths and yet still keep the same bracket and lower radials section for all of them if you experiment?)
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Re: .64 antenne plans wanted

Drew205216
Wow, I have a couple of TRC vintage handhelds and always wanted to attach about a dozen or more ground planes to the base(s) of the ever so famous 4 foot center-loaded telescopic antenna (1/4 wave??). That said, measurements, type of wire and gauge of wire are all important for radio propagation. Always learning and of course, it’s fun!!!!!