Help needed , dipole antenna for civil/miltery air ???

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WARLOCK
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Help needed , dipole antenna for civil/miltery air ???

Post by WARLOCK » 05 Jun 2017, 15:25

As i live in the fens and there is very little else to tune into please can anyone help i would like to make a dipole antenna to receive booth civil and miltery air if it is possable to build such a antenna ???

paulears
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Re: Help needed , dipole antenna for civil/miltery air ???

Post by paulears » 05 Jun 2017, 18:14

Well yes - the cheapo version uses a bit of chock block barrier strip, and a couple of metal coat hangers, a bit of coax with the right plug for the radio. Get a calculator and for VHF airband enter 300, then divide it by 120, then divide that by 4. This is a gnats whisker awy from the length of each bit of wire. You can add on say 10mm, then bend it at right angles and screw this into the strip. If you do the same for 300MHz, you can get them into the same hole, and have a dual band dipole. For aviation, using it horizontally like a turnstile works pretty well for all things up in the air.

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Re: Help needed , dipole antenna for civil/miltery air ???

Post by Admiral » 28 Aug 2017, 11:41

Here's my effort. Moved house and previous owners left miscellaneous crap in the back garden which included a rotten old gazebo thing, but when life gives you lemons you have a G&T, ally poles and plastic pole connectors, nice. Cable tie mounted to an old satellite dish bracket, resonates about 130Mhz. London Volmet on 128.5950Mhz is not there on my (genuine) Nagoya, in the noise and virtually inaudible (but I know it's there) on my generic (cheap) white stick, and S4 with strong audio on my ten bob dipole.

Skill level: Beginner
Time to make: 40m-1hr
Tools used: Soldering iron, drill, hot-snot gun, sandpaper, multimeter (to make sure of continuity after filing away the coating on the poles to solder to), the duct tape is optional, just used to match the colour to blend in as the connector is black.
Total cost: Pennies, co-ax and plug were the cost.

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Winner of the 2017 IBTL 'Summer Sizzler' competition

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WARLOCK
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Re: Help needed , dipole antenna for civil/miltery air ???

Post by WARLOCK » 05 Sep 2017, 09:35

Is it better to make a dipole for air band 1/2 wave or 1/4 wave ???

paulears
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Re: Help needed , dipole antenna for civil/miltery air ???

Post by paulears » 05 Sep 2017, 20:17

Oops. If you are making a half-wave dipole, then each bit that goes out from the middle, is a ¼ wavelength, so that's ½ wavelength end to end - and that is calculated for a single band. So probably centred around 125 or there abouts. This means that it's going to be good on VHF airband, but less so on UHF. Remember a dipole is NOT a wideband antenna, so results outside it's natural range will be ok, but not brilliant.

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