need a directional antenna design for a walkie talkie

[loosecannon]

Hi all,

Im trying to track down a major noise source in my neighborhood, and i would like to just use the walkie talkie i have and put an external antenna on it that i can point at the noise.

I have seen PVC tape measure beams for VHF but alas this noise is not picked up on my 2 meter talkie, just the HF band is affected.

so does anyone have a cool website or design for something i can put together?
I am going to use my CB walkie talkie as i don't have an HF rig that i can walk around with, so the antenna will be tuned for 27mhz.

thanks!
LC

 

[w9cll]

http://www.arrowantennas.com/sub/arrowiiyagi.html

 

[w9cll]

https://www.jpole-antenna.com/2017/02/07/build-it-2-meter-tape-measure-yagi-beam-antenna/

 

[nomadradio]

Built a loop antenna from a 1-foot diameter ring of copper tubing 30-plus years ago. Plans came from a 1970s magazine, long forgotten. Used it to track down an aggravator. Told him the names of the streets around the block where he was located and he got suddenly quiet.

It was used by finding a null in the signal strength as you rotated it. Much sharper than the peak signal you get broadside to the loop.

It's bidirectional, but taking a compass bearing from each of two separate observation points gets you a triangle on the map. Your signal is where the two lines intersect.

A beam antenna with enough elements to use for this purpose will be the size of a normal 11-meter beam, and not really "portable".

Plans for this kind of antenna are out there somewhere.

73

 

[loosecannon]

thanks for the replies guys.

Nomad, did you have to add any series capacitance to tune the antenna or can i just twist together a coat hanger and shove it in the antenna socket of the handheld?
LC

 

[Slowmover]

“. . not really portable”.

Ha!

.

 

[nomadradio]

Seems to me that the loop was broken at the top and had a mica compression trimmer capacitor across the break to resonate it. Can't remember the feedline hookup. Pretty sure the braid soldered to the bottom of the loop, and the center conductor partway up one side. Didn't bother with a gamma match capacitor. SWR was no big deal, since it wasn't used to transmit.

It's been over 30 years IIRC, so details are hazy. Pretty sure the article was from either "Electronics Illustrated" or "Popular Electronics" of the early or mid-1970s.

73

 

[Wire Weasel]

I have found that an ordinary AM Broadcast portable radio makes a great Noise Detector. Any AM/FM portable radio set to AM .... do that walk-around thing. It'll find the noise source for you.

 

[loosecannon]

well i threw this together in a couple of spare minutes i had this morning LOL

, and while there does seem to be some directionality, it seems like it works best when held horizontally with the loop oriented so you could look down through it and see the ground.

i caused some strange looks in the dogs out in the back yard spinning in circle after circle.

i think i need to try it in a few locations to really tell if its giving me a direction or not.
thanks for the help so far.
maybe i'll add a trimmer cap.
i think i have some 50-400s around here
LC

 

[nomadradio]

Uh, okay.

This is not even remotely close. Gotta find that article.

Does this radio have an external antenna socket?

Gotta have one to use this trick. The antenna needs to be connected both to hot and ground side, not just in place of the whip antenna. You really need a radio with an external-antenna socket for this to work.

73

 

[Captain Kilowatt]

Here is a start

https://sites.google.com/site/smalltuneddfloop/

 

[Mudfoot]

Use VHF yagi to get general area. Switch to UHF to pinpoint.

 

[groundwire]

Make a homemade rdf antenna, they aren't to hard to make

 

[loosecannon]

Uh, okay.

This is not even remotely close. Gotta find that article.

Does this radio have an external antenna socket?

Gotta have one to use this trick. The antenna needs to be connected both to hot and ground side, not just in place of the whip antenna. You really need a radio with an external-antenna socket for this to work.

73

LOL i know that's not what you were talking about.
I kind of put that together and took a pic of it because i thought it would be funny, but then actually took it outside for a minute when i put the dogs out.

i imagine this is similar to what you are referring to, and maybe when i get some time i'll put one of these together.
LC

 

[Woody-202]

Hi all,

Im trying to track down a major noise source in my neighborhood, and i would like to just use the walkie talkie i have and put an external antenna on it that i can point at the noise.

I have seen PVC tape measure beams for VHF but alas this noise is not picked up on my 2 meter talkie, just the HF band is affected.

so does anyone have a cool website or design for something i can put together?
I am going to use my CB walkie talkie as i don't have an HF rig that i can walk around with, so the antenna will be tuned for 27mhz.

thanks!
LC

I've used this one (oldie from EBAY) with success. It has a small variable capacitor at the top of the loop.