Construction Details Of Yagi-Uda Antennas

Element fixing details (DJ9BV style)

A detailed picture of the 4mm-element fixing (here a 70cm yagi)

Drill a hole in the boom and press the rivets in. But pay attention not to squeeze the rivets to much or even crush them. At higher temperatures the nylon is more soft so you can 'heat' them up maybe by putting them into warm water, it is easier to work with. Remove the nylon pin and strike the element through the rivets but support the lower one otherwise you push it out of the boom. To avoid damaging the element you use a 'sleeve' i.e. a hard wood. You can put a bevel (45°/1 mm) at the end of the element to lower the friction and reducing sensitivity to rain.

the used nylon rivets

These rivets ( a product originate from the USA ) are obtainable in Germany at [1] and in the UK at [2]

// a closer look at the driven element.....still to come

Details of the DK7ZB 28 Ohm yagi construction

See the complete polyamid holder at the above picture. For the antennas only the bottom part is needed (much cheaper ! ). Of course you can use the above method using through the boom mounting like DJ9BV adviced, but this method only works for 4mm elements. If you have an element diameter other than 4mm you need a different holder ! These polyamid holders are ok for elements (tubes) with 6 - 10mm in diameter.

A very difficult diameter is 5mm. Although better mechanic is provided fixing these elements is not easy. See a possible solution of 5mm yagi element holders below.

Holder 5mm yagi elements

These are the only 5mm element holders I am aware of here in central europe. They are very diffciult to obtain, so far the only one I could get ! They have been produced by Sandro, I0JXX to be used with his own yagi antennas he is developing and producing. BUT unfortunatelly he doesn't produce them anymore because it is to expensive to do it as a single holder. So for all 5mm designs, especially the popular BVO series de DJ9BV/DUBUS the problem remains how to fix the elements insulated through the boom. If there is no redesign using 4mm elements I can't see any solution at the moment.

Update

Met Sandro at the 'HAM Radio' festival end of June and he had promising news. Due to many requests he will produce some new holders around Sept./Oktober availible ! Ok, now online at his site: Yagi element holders

Call for 5mm yagi element holders in europe I'd like to ask amateurs all across europe to look out for additional sources of possible yagi element holders. So far there are the classic nylon rivets widley used especially for DJ9BV yagis. These are right for 4mm aluminium rods. Newer designs sometimes use 5mm elements for mechanical and electrical reasons. Also the english world using 3/16" for lightweighted designs that must be recalculated to 4mm only because no element holders are available. The shoulder washers I used are specially founded by a local ham who provided the necessary tools. But this possibility has gone now and no greater number of holders is available. One solution maybe nylon screws that could be drilled to take up the element, similar to the delrin founded holders I0JXX did. I think it should be possible to find something somewhere in europe. Everybody who could help pse send me a mail: 5mm holders found

More yagi element holders

[1]

[2]