Yet another antenna build thread

I fly helicopters on the side (not my day job...yet ). Whenever we are operating at some random location for the day we have found that the handheld radios ground personnel use don't really cut it with their stupid rubber duck antennas. We know those tiny, electrically short things are made for convenience, not performance. Since helicopters typically fly low, between 500 and 1000ft AGL, there is no line of sight advantage associated with having one radio airborne. So we will get maybe a couple of miles of range out of handhelds for ground-to-air comm's.

In an effort to flex my RF muscles I built a quick and dirty vertical out of some cut up coat hangars and duct taped it to a painter's pole. It worked very well, achieving 6 miles over flat but wooded terrain. So now I needed to build something a little better. I wanted it to fold up for easy transport in a helicopter, require no assembly, and attach to the ubiquitous painter's poles. Here is what I came up with:

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It's tuned to 123MHz because that's where all the freq's we most commonly use are (e.g. 123.025 heli air-to-air, 123.45, 122.9 multicom, etc.). In testing the tape measure radials tended to flutter in the wind but surprisingly that barely made the trace on the NanoVNA waver.

I still need to engineer a strain relief for the vertical element. I'm thinking of gluing or screwing a PVC cap over the connector assembly with a hole for the vertical element to take the strain off of the solder connection. I'll probably have my XYL sew up a cordura nylon drawstring bag for it, too.

I bet you could replace the vertical radiator with tape measure inside some heat shrink like a "tactical blade" antenna. I think the shrink tubing makes it stiffer than without. I want to replace the elements on my 1/4wave 2m antenna like that as it's hard to transport without bending the radials.

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I'm happy with the 1/8" brass rod I'm using as the radiating element (I tried to find aluminum but all they had was brass at Lowes, not that it makes any electrical difference). I would be too afraid that the vertical element would wander a bit in the wind using the tape. However, that is a very good idea in that I'm wondering if I add a little heat shrink to the radials it will keep them steadier in the wind but still fold OK. That's an easy experiment, but I think I need to go buy some large diameter heat shrink.

Antenna build threads are best threads.

You should make a slimjim and instead of hanging in a tree, hang it below the helicopter by just throwing it over the side once airborne and since it is just 450 ohm ladder line, you can land on it no problem if you forget to bring it in

This is super cool, and I’m gonna steal this idea for when I go to my parents’ place.

I’m also curious about your job. That sounds way cooler than doing helicopter stuff over a VPN.

I design and build "cool" stuff for our lords and masters. Well, I used to do the direct designing and building. Now I am a senior principal systems engineer in charge of overall design. In the old days they would have called it "chief engineer". Think Kelly Johnson but not airplanes, instead it's large, complex RF electronic systems. If you are military you've probably seen, or possibly even used/relied upon, some of the stuff I've worked on. [forest]And that's all I'm going to say about that.[/forest]

Haha sounds like we actually have pretty similar jobs, only I deal with the mechanical integration part of it, and as a junior engineer. I’m hoping I can leverage my interest in RF stuff into getting into EMC and cosite type stuff soon.

But yeah, that’s all I’m going to say about that.

Some moar photos: PVC strain relief, plastic bead tip protector (stolen from my XYL's bead box ), and additional detail on the construction. Still need to get some shrink tubing.

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Very cool!  It's clear you have skills! Nice job!

that looks awesome.

Give us a pic of the whole thing.

That is a great base

The more modern tape whips place the tapes facing each other like this ( ) and then heat shrink them so they structurally support eachother but still collapse and bend.

You learn something new everyday

Thank you!

That was most excellent advice. I am going to make a "tactical" 1/4wave next time I go to horrible freight and can pick up some tape measures. I want it all to fold /roll up and fit in a little bag.

If you don't have heat shrink that large, you can run tape up the sides.

of the helicopter.

Dumb question: I assume the antenna is a temporary, field antenna and it will be used in a stationery manner. Have you considered using a telescoping whip for the vertical part?

Also, look up "Kulikov antenna". It's a Soviet military antenna that can be used as a flexible vertical whip or it can be coiled when transported. It literally takes seconds to bring it from the coiled shape to a vertical position. Very ingenious design. Ebay has them for sale. I've been thinking about getting one.

That's another neat idea. Reminds me of a tent pole. I've thought about making a tripod mount for some spare aluminium tent poles I have that are ~12' long.

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Exactly. You did see the photo on the painter's pole in the OP, right

SHHHH! You are giving away my next evolution of the design!

Indeed I have. In fact I think the next version will be much better. Telescoping elements for each part. Radials will fold, too. I ordered the telescoping parts off of Amazon this morning. Along with the shrink tube, because I really do want to finish the original. I'm even going to try to cut some more tape measure tape to do the back-to-back thing on the radials. I think I'll paint the entire thing OD, and with the black shrink tube it'll look very military

I can't see how that will outperform the quarter wave vertical.

There used to one made with telescoping antennas like on FM radios. It was for 2m/440/220 depending on how many antenna sections you extended. I bought the last one that was sold a few years ago. I keep it in my suitcase to use with an HT when I am in motel rooms.

It won't be more efficient. I like the design features and it's ability to go from folded to extended vertical in seconds. I'm sure it can be trimmed and modified to resonate on a VHF frequency.

VTW, I've seen permanent antennas on painter poles.

So I investigated the suggestions of Nmbmxer and mancow. Adding just plain old shrink tube to the entire thing makes the radials droop, they are too heavy. They only need the extra stiffness near the root. I added a 6" piece of tape in the suggested () orientation and covered that with shrink. That helped a lot. It's not perfect, but it definitely cuts down on the waggle factor <--technical term And it made no difference at all in the VSWR of the antenna.

At this point I'm pretty much done with this one other than painting it. I don't know if the paint will adhere to the tape very well when it flexes. I'm going to take a piece of scrap tape and test paint it.

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Also, the parts for the next version are in. It will undoubtedly be much smaller, but it will be much, much more vulnerable to damage. Those telescoping rods will be mashed if it ever falls over in use.

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excellent thread !

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This is purely awesome, OP.

Thanks, gents

Krylon camo ultra flat olive seems to work nicely on the tape measure material with a thin coat. Unfortunately it's too cold to take the entire antenna outside for painting probably for at least a few weeks.

There will be a slight delay before I start the version with the telescoping rods. I need to fix my inverted L first.

Got alot of that on my guns.

I don't think it'll hold up to the folding very much.