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 Portable 28 MHz (10 Meter) 2 Element Beam
Using 102" Steel Whips


The old standby 102 inch steel CB whip has been around for a long time and used on the amateur bands by many hams over the years. This design will incorporate four of the steel whips and allow us to concentrate our signal to a specific area and give us 3 to 4 dBd to boot (*)! It is direct feed with 50 ohm coax. It will also be easy to assemble and fairly transportable at a cost of about $100 depending on how you connect the whips to the boom or use new or used materials. Here's a method I chose which will make it a snap to assemble and install in cold weather, field day, etc.

Version above is for 28.450mhz

A 102 inch steel whip is a quarter-wave on the CB band (27 MHz). Using the N3DNO antenna calculator we arrive at the following dimensions for our desired frequency of 28.450 MHz (+-): driven element is 8 ft and 4 inches long each (there's 2 for a total of 16 feet 8 inches), the reflector is 17 ft and 7.3 inches long with the spacing at 6 ft and 7 inches from the driven element. Note that the reflector is one continious piece electrically. (Not insulated from the boom.)

Now, keeping that in mind, and trying to maintain the 8 ft and 6 inch length of the CB whips (I didn't want to cut the whips down as I may want to reuse them some day for other projects) we find these dimensions (trial and error using the above antenna calculator): for 27.8 MHz the driven element is 8 ft and 6 inches long (the actual length of each whip+-) on each side, and the reflector is 18 feet long (**) with a spacing of 6 ft and 9 inches. The difference in the desired frequency of 28.450 MHz vs. the "not to cut the whips" frequency of 27.8 MHz is only .650 MHz which should be easily handled by any antenna tuner.

To mount the whips to the boom, you can u-bolt a short piece of "L" channel (+- 6 inches long with the predrilled holes) to the boom and then mount the antennas to that using insulated connectors for the driven elements and non-insulated connectors for the reflector.

(Or if you are like me and want something a bit more attractive, you can use a pair of
commercially made mounts (MFJ mini dipole mount #347 or others like in the picture above).

The 102 inch steel whips are available from DX Engineering (#DXE-WP-102) or through Radio Shack (?). This design may also work on 12 meters as well. This antenna is in the experimental stages, but the above dimensions should be good starting points, and you may chose to cut your whips down to the design dimensions above.
Keep in mind that whether or not you use the commercial mounts on the reflector, or your own mechanical design, that you will have to make certain both whips are connected together forming one continious electrical connection. Other wise it will not work! If you have trouble tuning for lowest swr or just don't want to bother, then use your tuner. A 1:1 balun at the feed point is also suggested.
Any and all feedback is appreciated. 73 de Yukon John, KL7JR
kl7jr at Yahoo.com

*See "2 Element Wire Beam for 28 and 24 MHz" on this website

** You can add 6 inches of wire to each of the 102 inch whips to get the 18 ft length, or not. Experiment either way.

Recent Comments from builders!

"I was bored yesterday, and was surfing the net for an antenna I could build with what I happen to have around the shop here...
I had to gain the height by placing the antenna mast onto my motorcycle trailer and then run it from my 2000 Mercury Sable LS, using an Yaesu FT-817ND with a LDG Z11Pro Autotuner and about 50ft of RG-8X that mostly came from Radio Shack..."

"About 14:53 Hours EST, I made QRP contacts with KJ9B in Honduras, and later made contact with PU5OGE Evan in Corocheba Southern Brazil on 5 watts."

"Wow, I built the antenna in about an hour, with parts that I had just laying around drawing dust, and was able to make these contacts....the Skip was great, and even heard Argentina, but was unable to confirm contact...Thanks for such a great Idea... 
I will be building my next antenna from the formulas from this project below:

2 Element Wire Beam for 28 and 24 MHz


Robert KJ4OTZ
Graham, North Carolina 27253




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