446MHz Slim Jim Antenna

Anything related to using and/or building PMR446 Antennas
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TM205
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Joined: Fri Oct 29, 2021 12:42 am

446MHz Slim Jim Antenna

Post by TM205 »

Image

You can place it inside plastic waste pipe for outside mounting.


:thumbsup:
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dc260
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Re: 446MHz Slim Jim Antenna

Post by dc260 »

TM205 wrote: Sat Jan 22, 2022 12:55 pm Image

You can place it inside plastic waste pipe for outside mounting.


:thumbsup:
Great design and would be discreet for outdoor mounting, any ideas on the SWR values you get from this design?
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TM205
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Re: 446MHz Slim Jim Antenna

Post by TM205 »

Its fairly wide band down to 441.5MHz and up to 449Mhz Obviously that was using thin wire. If you use thicker diameter tubing the bandwidth with improve slightly. But it isnt really needed. The hardest bit was getting a good vswr match.
Which I found a bit hit and miss until I found a break in my coax.
duuuhhh!
Anyway give it a build and let me know your results.
When mounting it in plastic tubing use thick fishing line to hold it up at the top of the tube.
That way you can use longer tubing to mount it to a pole and the pole should not effect the tuning of the slim jim.
You could also fit a socket in the bottom of the plastic tube say an so239 or N-type. then you can use better quality coax to feed it.

:thumbsup:
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Re: 446MHz Slim Jim Antenna

Post by Username »

Tried it, well, I used a calculator but a slim jim none the less.
Worked well, massive faff getting the SWR right though.
Solder coax on, up the mast, check, nope, down the mast, unsolder, move the feed point, solder, up the mast, check, nope, down the mast, unsolder..
Yawn!
Got there in the end but wasn't suitable of my application although it was light and easy to carry it was a pain to attach to a mast nicely.
As an aside, you only need to mount the section above the gap in free space, the lower part is simply a matching section and matters not how that's mounted, they can even be bent 90° and still work okay.
:)
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