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Dipole on 2x4

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wjm1129
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Dipole on 2x4

Post by wjm1129 » Saturday, 17 June 2017, 21:53 PM

I am planning on building a modified t2lt vertical with a 102 inch whip as the top radiator. I want to use a 2x4 as a mast. If I secure the coax/bottom half to the 2x4 will there be signal loss or tuning problems. All opinions and suggestions welcome. Thanks.


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Re: Dipole on 2x4

Post by Bluerunner » Saturday, 17 June 2017, 23:01 PM

102" will be a little too short. Add a piece of stiff wire to the end to get to 108". Wrap the end of the wire around the whip and you can slide it up & down to change the length for tuning.

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Re: Dipole on 2x4

Post by MDYoungblood » Sunday, 18 June 2017, 16:30 PM

I believe the whip would need to be about 104", so a couple of mounting nuts stacked will give you about the right length. I wouldn't tie the coax against the 2x4, make some standoffs out of PVC pipe about a foot. Cool antenna, got to play with the measurements to get the SWR right and seal the coaxes braid so it doesn't draw in water or moisture... Good luck with it.

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Scipio Kid
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Re: Dipole on 2x4

Post by Scipio Kid » Monday, 19 June 2017, 19:30 PM

What Greg said about sealing the coax ... years ago I'd use RTV (silicon seal) which is readily available anywhere but I found a better choice was Scotch-Coat electrical coating which we used anyway in our business for underwater high voltage splicing. It's phenomenal, but expensive and messy. Get it on your hands and you'll know it for more than a week. Get it on your jeans and you'll have a new custom design on your jeans, forever. A real good alternative is Liquid tape. You can get it in a number of colors (if it matters) and it's inexpensive at Lowe's or Home Depot. It doesn't run or drip like Scotch-Coat (maybe a little if you get it too thick) and it dries a lot faster. I use this stuff anywhere I have bare wires or splices especially when wrapping something with tape is difficult. If you have an exterior or moist location where you've insulated with electrical tape, I'd highly recommend you coat the tape with it too. Do it right and you'll never have to worry about your coax deteriorating. It dries flexible so it won't peel or crack either and it helps stop wire flexing and eventual breakage of your coax conductors.

So far as length goes, with the 102", like the others have said, you may need to experiment. It all depends on the reflective properties of your ground plane. I use a 102" SS whip with a 4" HD spring at my base in the desert and it's one of the best antenna's I've ever used, perfect SWR on all channels and gets out barefoot all over. At home, I have something similar with a fiberglass 102" with a smaller ground plane and went without the spring to get a good match about a 1:2 on channel 1 a little higher on channel 40. I'm not going to tune it further because it's experimental and I don't want to trim what I can't easily put back.

Good luck. Post a pic when you get it done and let us know how it works.
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