Dipole

[Uksoundz]

Hi,
I'm gonna build a dipole antenna this weekend for a bit of fun (don't get out much ha) i'm gonna get some of this:
http://www.diy.com/departments/ffa-conc ... 217_BQ.prd
but whats the best way to connect the coax to the elements, I don't have any fancy junction box like the shop bought ones so what do the DIYers here do?
If anyone has a link to some items I can pick up from b&q or wickes it would be nice!!
cheers

[radio-berlin]

Preferably you want one of these from eBay ... Item 400738574189

Or you could use some plastic pipe, I sometimes rivit my elements inside plastic pipe and then use 'eye' connectors and rivit my coax to the elements, I then fill the holes with silicone. Or in an emergency I just simply cable tie my elements to some make shift piece of plastic to act as centre piece and then joint my coax with crimps. It just all depends how skilful you are

[s2000]

Electricians teebox works well...

http://www.screwfix.com/p/tower-3-way-t ... oC5jXw_wcB

The inside is accessable and the spout is a 20mm fit so will fit directly onto 20mm electrical conduit if you use that as a mast (needs a 90 degree bend in it for boom).

Pretty much anything can be made from plumbers and electricians stuff...

[Uksoundz]

Ah so I could use that teebox, then some 20mm conduit for the boom. Would you use a couple of 4mm alu poles for the elements and cover them with more 20mm conduit?

[thewisepranker]

You can do, but you need to make sure that the plastic condut doesn't contain metallic pigments such as titanium dioxide. To do this, put a cup of water and a small offcut of the conduit in a microwave for a few seconds to see if the conduit gets warm. If not, then you can use it as you have suggested.

The cup of water is quite important as it is effectively a dummy load for the magnetron.

[s2000]

Ah so I could use that teebox, then some 20mm conduit for the boom. Would you use a couple of 4mm alu poles for the elements and cover them with more 20mm conduit?

I used telescopic aerials on mine as it was just experimental, low powered for a small rig I built. This allowed me to tune the aerial to whatever freq I changed too without cutting the elements.

If you know what freq you will be on, you would be better off using 15mm copper piping or similar. I wouldn't bother with putting conduit over the elements, as long as the centre box is weather proof, should work well... Also this type of element is better for higher power

[Uksoundz]

I remember when I were younger you could buy decent verticals from NRG or Veronica, these days I don't seem to be able to find anyone who sells 5/8 or 1/2 wave verticals anymore. Anyone know of anywhere cheap haha and in the UK?

[Uksoundz]

In fact, look at this below, could something like this be modified to use on band 2?
http://www.mcr666.com/sales1/ham-radio/ ... l-antenna/

[shuffy]

Ha ha, a silver rod. No reason why not. The base probably has a matching network in it, so that would need to be changed to resonate on Band II and then chop it down to the correct length.

[s2000]

Why not build a slim jim, they are easy to make and far better than dipoles..

[yellowbeard]

If you want to make a B&Q antenna then this one is superior:

Code: Select all

http://radio.xtreamlab.net/omni-aerial.html

Two lengths of waste pipe, some thick copper wire and an SO239 is all you need. Slim jims are great so long as you use a choke balun (say 5 or 6 turns of coax taped up just below the antenna) and get them up over 30 feet you will get out.

[teckniqs]

Ha ha, a silver rod. No reason why not. The base probably has a matching network in it, so that would need to be changed to resonate on Band II and then chop it down to the correct length.

I know someone in London who does this.

[shuffy]

I haven't seen a silver rod for about 20 years but I think it's basically just a tapped coil in the base with a loading capacitor, needing only a short counterpoise. A Steve Moss funnel antenna, in other words. What sort of performance does your mate in London get compared to a dipole? Have they done any measurements?

[shuffy]

Why not build a slim jim, they are easy to make and far better than dipoles..

Bigger though, and fed at the bottom. So unless you build it out of sturdy material (which is possibly harder to work with e.g. bending tubes without flattening them!) then you're going to find it more difficult to support than a dipole, which will pretty much support itself.

[thewisepranker]

You'll be surprised how much power a Ø4 mm piece of aluminium or brass (which is much easier to solder to) can handle. After all, something like Westflex WF103 has a centre conductor diameter of only 2.62 mm.

The trouble with copper pipe is that it gets quite heavy quite quickly, i.e. add a reflector using about £3 worth of copper pipe and a bit of blowtorch action, nice and easy. However, it now weighs four kilos, which you somehow have to support.

Considering you can buy this for £6 delivered: http://www.ebay.co.uk/itm/3-8-TO-3-8-DI ... 25aa511bb7
... And the traditional screwy ones for about a tenner delivered, why bother making one, other than not wanting to wait for delivery?

[pjeva]

Power is not a problem. Your home power installations have much thinner wire and hold killowatts. Problem is that thin wire makes very narrow bandwidth antenna. So you need to cut it right at frequency which is very hard without network analyser...