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1/4 Wave 70cm/PMR 446 Antenna

Started by OnTheMicwithMike, Nov 13, 2023, 11:37 AM

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OnTheMicwithMike

Just thought I'd show an antenna that I've now made a few of for people. It's a small quarter wave antenna for 70cm/PMR 446 and works rather well.

Very easy build, all you need are a few things and the results have been great.

You'll need:
- an SO239 chassis mount
- small copper or bronze 'brazing' rods (I got a pack of 300mm rods from ebay very cheaply)
- small packet of Nylock 'M2 sized' bolts & nuts with washers
- small pack of ring terminal connectors
- a dab of solder to secure the driven element into the SO239 mount

I also did a little YouTube video back at the time I was making them:
https://youtu.be/3BlqWm1FT_Y?si=doa7UucBT4gPuRvF

A few pictures:







They work really well, and I've used them at home mounted on top of a fibreglass pole with a small piece of tubing at the top so the SO239 socket can sit in place. I've also used them static mobile as well and results have always been good, way better than a stock antenna on a handy.

Just thought I'd share in case someone may like to try to make one.

73' all the best

14FRS119

Hello Mike  ;D

Thanks for these informations !!
Best 73
14FRS119  Jacky
Normandy France

Razz229


They are great little antennas.

I still use the first 1 given to me by Andy CT 1023 from Eastbourne.

It works well but doesn't look as good.

Do you think a half wave whip would work with those ground planes?

OnTheMicwithMike

No reason a 1/2 wave wouldn't work, the only thing with it is the driven element (vertical) would need to be around 33cm in length and the radials around 34cm give or take to get a good tune on 446. The other issue I found was I couldn't find brazing rods that were that long at the time I made the antennas lol

Razz229

Quote from: OnTheMicwithMike on Nov 18, 2023, 11:48 AMNo reason a 1/2 wave wouldn't work, the only thing with it is the driven element (vertical) would need to be around 33cm in length and the radials around 34cm give or take to get a good tune on 446. The other issue I found was I couldn't find brazing rods that were that long at the time I made the antennas lol

But would you need longer radials or just more radials?

4 for a 1/4 wave, for a 1/2 wave add another 4 radials the same length as a 1/4 wave or am I just thinking a bit to simplistic?

OnTheMicwithMike

Just longer radials I'd try to start with. Can always add more later on with wire to the small nut & bolts :)

Razz229

Looking into my cracked crystal ball. . . .

 . . .  I can see a 1/2 wave 'sputnik' antenna in the future

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