Web Updated;
06/07/2011
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Assembling the aerial.
Adding the RF Choke.As the aerial is unbalanced, common mode currents could travel down the feed line. The easiest way to stop this happening is to add an "RF Choke" in series with the feed line as close to the aerial as possible. This one is made from a large diameter hot chocolate tin (empty of course!) which is approx 75mm in diameter. 15 turns close wound covered with plastic insulating tape. (holds it in place)
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Putting it all together!The top part of the aerial (whip) is made of telescoping fibreglass sections. You can find the manufacturer of these poles under my favourites or click here! This is connected to a piece of 25mm x 25mm steel angle and secured using rubber bungee straps. The coil is mounted onto this steel section. and the wire which runs through the whip is connected to the top of the coil with an electricians "chocolate block" connector. Don't forget to strip the enamel off the ends of the wire before connecting into the blocks. The bottom of the coil wire is connected into another "chocolate block" connector and this is also where the counterpoise connects. (you can see the counterpoise as the blue wire coming away and down to the floor). The whole thing then mounts onto a tripod (sold by Maplin's) which provides a sturdy support. |
For a detailed drawing of the aerial please click HERE (required acrobat reader)
For the aerial specification please click HERE (required Microsoft Word)