Tuesday, May 14, 2019

Big wheel antennas for VHF/UHF horizontal polarisation with gain

VHF / UHF SSB operators normally use horizontal polarisation. Beams are easier to erect as there is no need to use a non-metallic mast. And there are some other advantages of being horizontal, for instance it being better for tropospheric propagation.

The main disadvantage of being horizontal is that almost all antennas are directional.  That's a problem if you're mobile and you're going around corners. Or you live in an apartment building and don't wish to put up a large beam and rotator.  One possibility is the halo that we discussed previously. However it has little gain. 

Another possibility is the 'Big Wheel'. It's still omnidirectional (in the horizontal plane) but it has a bit of gain. It comprises three full wave loops in parallel bent around a bit. Think of a Mercedes logo high in the sky. They draw attention if used on a vehicle but, believe it or not, ardent mobile VHF SSBers use them. And they're not too conspicuous if at home provided you can mount them high enough. If you're really keen you can stack two for more gain. Even if you already have a beam for VHF a Big Wheel can be handy to  have as an omnidirectional antenna for casual tuning around. Then when you find a weak signal, possibly due to a bit of lift, you switch to the beam and hear it better. 

Here are some Big Wheel articles and ideas: 

PS: Want even more practical antenna ideas? Consider this selection of antenna books. They are affiliate links meaning that I receive a small commission (at no extra cost to you) if you decide to purchase.


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