Tape measure Yagi

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KF5YDR

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Jul 24, 2014
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There are fold-up ones home-brewed from tape measures that stow neatly in cardboard shipping tubes. They pop out as you draw them from the tube, and auto-stow when you jam them back in, it's pretty cool.
I'm familiar with tape-measure Yagis, but I'm curious how the elements are mounted that allows them to stow just by jamming the boom into the tube.
 

PrimeNumber

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I'm familiar with tape-measure Yagis, but I'm curious how the elements are mounted that allows them to stow just by jamming the boom into the tube.
Darnit, I wish I had more details. A friend a county over who's all into foxhunts whipped one out after a club meeting a couple of months ago. Everybody went "holy crap!" at the noise, and suddenly there was this 2m Yagi in the guy's hand! It looked like the elements just collapsed down onto the boom as it was inserted, snapped out as he unsheathed it. I'm going to build one fairly soon, will post details when I do.
 

teufler

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ST PETERS, MISSOURI
tape beam attachments

in reference to kf5ydr's request, these photos show how it can be done or why "beefing up" the connections to the boom make sense.4528 shows the reflerctor attachment. small inserts are placed at the boom attachment point because over time, the elements develop cracks and you lose an element, at the worst times, or you develop a tear and the metal tape is SHARP, .4529 is the director,which has the element sideways so its more sturdy in the wind. Imagine, looking at the beam attachments, if the tape element was facing forward, the wind will collasp the beam elements quickly though if you want to stick the antenna in a tube, that s exactly how you would insert the element. 4530 shows the 3 element boom and how all the elements are or in, my case, inserted. I use mine for mobile fox hunts and direction finding mobile. The center element is taped to a 3/4 pvc tube that sticks out the moon roof of the car. The black tube at the rear of the beam is a pvc trap pipe for a household sink drain. It makes a good hand hold. When I operate that way, you can scare the crap out of people at a stop sign as the elements have collasped while you are in motion but quickly expand when you come to a stop. You drive down the street resting the boom on the outside mirror. The elements spring to life at a stop.So the drive element and the reflector element are sideways to the wind. The director element is inline with the wind. As soon as it breaks, a new one will be inserted like the other two elements. If all elements are inserted like ther driver, they all collaspe in a tube. When I travel, the boom comes apart so no boom pieces are longer than 12". The elements roll up and I take safety pins to hold them in a roll. The whole thing packs in a suit case for air travel. You really have some excitment when TSA opens the suitcase and an element springs out. The center pieces are 3/4'pvc 4 and 3 way connectors. A small insert , made from 3/4: pvd is inserted and squeeze the elements in place and a sheet metal self taping goes into to lock the insert in place. The reason the boom is silver and the elements are yellow was a stupid refinement I made when I first built it. I thought it would look better all silver so I sprayed everything silver. Now silver is a metal base paint, so the driver and the elements were grouned all together. As can be expected, SWR was off the scale. So once the refinement was taken out, the swr was set with a mfj analyzer, the t match was flat. The t match photo shows how the coax attaches to the driver, and is routed inside the boom rather than outside where the wind can play havoc. Some designs have construction with 1/2" pvc. wellk the tape is wrinkled going in the boom connectors and generally 1/2" is flimsy so going to 3/4" was not much of an increase in cost and a whole lot better construction. Some of the designs use hose clamps for all tape, which increase the cost. The only hose clamps I use are for the driven element as that allows fort the driven element adjustment.
 

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