We've all seen the pictures of chaps who can put up humongous beams on 200 foot towers. Unfortunately for most of us this is simply not possible. Most Hams in the UK are handicapped by small gardens (50 foot or less), or sometimes no garden at all in which to put antennas up! So what do you do if you want to work reasonable DX on the HF bands? Whilst it is true that sometimes you can work all over the place with the odd piece of wire slung up at 30 feet or so, or a low dipole (less than 1/2 wave over ground), most of the time such a setup will be found to be poorly inadequate.
20 Metres and above
For the bands above and including 20 metres it is desirable to have some kind of beam although reasonable results can be obtained from a multiband vertical. Unless you live in the clear on a hill, you would be well advised to mount the antenna on the roof, or on a pole as far off the ground as possible. Of course a ground mounted vertical will work, but no where near as well as one that is mounted up higher. Listen to some of the eastern European stations who have verticals mounted on top of tower block flats and you'll see what I mean about the effectiveness of mounting a vertical on the roof! With a ground mounted vertical you have to put a lot of effort into burying radials (more on that later), whereas with a roof mounted vertical you need as few as three radials.
Beams in small gardens.
So what about beams? Well of course most HF beams tend to be on the large
side and often it is not practical to erect one in a small garden. There
are various minibeams on the market although most of these perform like
rotatable dummy loads and often will not outperform a horizontal dipole
mounted at the same height. However, the Butternut HF5B minibeam does
actually work and covers 20-10m including 17 and 12m (dipole on 17m).
Each element is 12 feet long and there are no traps for tuning. The turning
radius is only 7 feet, and it can be mounted on a standard aluminium pole
attached to the house. Quoted gain figures are around 5dBd (15-10m), and
3dBd (20m). For optimum performance you need to get the beam 30 feet above
ground at a minimum. Some other manufacturers such as Cushcraft have recently
introduced new minibeam designs to the market that may provide useful
gain figures. You can also think of a magnetic loop for 160 80 If you
can remember listening toTony GW4OGP who is now silent key.
Be aware that most commercial minibeams are not much cheaper than their full size counterparts (at least not in the UK)!
For the homebrew there are also plenty of antennas for small gardens outlined in the excellent 'HF antennas for all locations' by G6XN, including some mini-beams that should in theory produce acceptable performance such as the VK2ABQ beam for 10/15/20 metre bands.