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I've been poking around the internet on how to make a Yagi for my HT. I understand all the math for cutting directors and reflectors to length and placing them at the correct spacing for 146.52 mHz. However, I keep finding different descriptions on how to make the driven element, or worse, no description at all.

How do I make the driven element? More importantly, how do I make sure that the antenna is 50 Ohms? Preferably, I'd like to not solder.

user6099
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3 Answers3

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Pulling it off without soldering will be tricky, your only option will probably be to get a chunk of coax with the connectors already on it, cut off a connector, then use bolts and crimp on lugs to connect the coax to the antenna element.

You're finding multiple descriptions of how to do it because there are multiple ways of doing it depending on the intended use of the antenna.

  • You can feed it directly like a dipole, splitting the driven element in two and connecting one side to the coax shield and one to the center conductor of the coax. It will not be possible to get maximum bandwidth and maximum gain with this method, though you should be able to get a reasonable compromise that works on all of 2 meters. 70cm would be much trickier.

  • You can feed it with a gamma match. This gives a wide match and has the advantage of also acting as a balun. They're finicky to make, and would be very difficult to tune without an SWR meter or antenna analyzer

  • You can feed it with a hairpin match. Similar problems to the gamma match, but similar advantages.

Personally, I'd recommend finding a design that specifically calls for a directly driven element. Google for NT1K Tape Measure Yagi for a good project write-up.

Another option if you don't need portability would be to ditch the yagi and build a cubical quad instead. There are many calculators available online that give you all the required dimensions, and they tend to be a bit more forgiving on the SWR front. They also provide more gain per element than a yagi, at least until you get out to about 7 elements. They can be made very inexpensively out of PVC or wooden dowel and 1"x1" hardwood lumber for the boom and wooden dowels for the spreaders.

Hamsterdave
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I made my 5 element with the driven split element like a diapole. I used cu tubing flatening one end and screwing them to a wolmonized square boom about 1/4" apart on boom direct feeding coax with terminal lugs. Of course you must drill hole in flattened end for wood screw hole.Cut them a little shorter than wanted length,about 1/4 inch. I used ss cotter keys at both ends of driven sliding them equal distances in or out to match. Worked great,flat match for 5 element beam.

Rocky Geiser
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The easiest way to make a driven element for a hand-made Yagi, without having to solder is to get out a knife+some elec. tape or heat-shrink tubing and make a 'bazooka dipole' antenna from your feedline coax & use that for your driven element.

  • Advantages:
    • Quick & easy to make, with absolutely no soldering necessary.
    • Forms its own balun, so you don't need an impedance-matching network added to your feedline, or your yagi.
    • If damaged, a 'new' D.E. can be made simply by re-cutting & inverting the same feedine (until the feedline gets too short to be practical, at least).

  • Disadvantages:
    • Feedpoint impedance is not easily adjusted, so you'll have to be careful to place your elements in an arrangement that closely matches your feedpoint impedance to your coax's characteristic impedance (Antenna simulation programs are available for free download on most platforms to help with this).
    • Your D.E. won't hold its own shape well, and will most likely need to be supported in order to maintain proper element alignment/spacing.
Robherc KV5ROB
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