A Great Starting Point For Novices –
Build a Simple VHF Dipole Antenna for 2m
If you’ve ended up here, you’re either a novice – or clicked through out of curiosity. We were all novices once, and my aim here on this page is to give the novice and beginner an introduction into building a working antenna. It’s not about the ‘Ins’ and ‘Outs’ of it all. You find no maths, physics [or very little] but we’ll try to explain in the simplest terms on how you get a simple antenna to work that will not cost alot.
There’s no point spending many hundreds of ££ $$ or €€ in the early days when you’re just getting to grips with the hobby. So save your cash, spend it on something more worthwhile or treat your XYL/Girlfriend/Boyfriend/Partner [we ain’t fussy here!] and I’ll show you how to build yourself something for the price of a sandwich and coffee!
So – what’s a dipole? …’DI‘ = 2, ‘Pole‘ – well a pole is a pole in any language. In essence ‘2 POLES‘. Each pole forms one part of the antenna. The 2 poles are separated [no continuity] and have a small 1-2cm gap between them. A dipole is one of the simplest forms of antenna. It’s a great ‘No-Fuss‘ affair that even the most inexperienced user can construct.
Let’s look at a ‘dipole’ that would be useful for the 2m VHF amateur band. Many novices will own a VHF radio which allows local and semi-local communications. Novices should firstly be aware that although connecting your coax from your radio to your antenna is a fairly straightforward affair, the type and length of coax at VHF plays an important part too. You’ll need a length of low-loss good quality 50 ohm coaxial cable.
At VHF, some long runs of coaxial cable can be lossy. It does of course depend on the type of coax you use and how long it is. We’d advise you to steer clear of ‘RG-58’ types of coax and so called ‘skinny’ cheap and low-end cables. It does you no favours installing these and it’s best to get something a little more up to the job.
So, let’s take an average installation. Your ‘Radio Shack’ is located in a house [upstairs or downstairs] – it doesn’t matter where. We’d suggest running a length of ‘RG8-X’ or Mini8 [just enough to reach the antenna] which can be obtained by the meter from outlets such as ‘Nevada Radio‘ [plug for Mike G3SED].
My suggestion is to mount the antenna VERTICALLY just above the ‘eaves’ of the house, but set away from the metal pole that supports it by at least 50cms [a little more will do no harm]. Antennas mounted in ‘The Clear‘ without nearby obstructions work better as other metallic objects close by can interfere with their operation. Check the diagram below [or click for a PDF] and all will become clear.
RG8-X or Mini8 is a great flexible low-loss coax. There are of course many other ‘Low-Loss’ variants around [including plenty from EU] but it has very nice reasonably low loss figures at VHF so can be used for lengths of say up to 20m without too much attenuation. It’s also flexible enough to include a home-made ‘Choke Balun’ at the feed point. This ‘choke’ prevents the RF from travelling back down your coax. We’ll not talk more on the ‘why’ its included in the design. Just be aware that it’s good practice to include it in your build.
If you wanted to ‘Go Posh’ with the mounting clamps, then our friends at ‘Pipeline Products Direct‘ stock the complete range of ‘Stauff’ standard and heavy duty clamps.
That’s it and all there is too it. Put a PL259 plug on the end of your coax and hook up to your radio. If you’ve done everything correctly, you’ll have a nice working antenna with a low SWR across the whole of the 2m band. For purists, you can check the SWR [Standing Wave Ratio] with an SWR meter suitable for VHF.
If you need a supplier of wall brackets and all the mounting hardware, our friends at ‘Barenco‘ will most likely be able to help you out!
Good luck with your project!
73 – Steve G0UIH/VK2IAY – Q82.uk