KC8AON,
Very interesting. I have been researching antenna efficiency. As most know this is the percentage of radiated power/input power to the antenna. So far in my research, it seems, that dipoles give you the best results and therefore the most power radiated into the ether. Of course that is for the frequency which they are cut and for the bandwidth of that antenna.
Do you or anyone else have any ideas or suggestion on what would be more efficient? The real battle hear on transmit is total power radiated while the battle on receive is signal to noise ratio. I have found a site and have been reading at http://www.antenna-theory.com/ that gives a lot of information on antennas but input is welcomed and desired.
Mahalo,
Edward
Hi Edward,
The "best antenna" depends on the space you have, and if you are not into construction on your bank balance too!
Total power radiated isn't the complete answer although transmission line loss is an important consideration as are losses due to mismatch. The other important factor to consider is getting the radiated power going in the best direction for the station/s you want to contact.
A simple dipole can work well though the height is important, if it's too low you'll get high angle radiation which is great on the LF bands for local contacts but not great for DX. A sloping dipole will give a little gain in the direction of the slope and adding a reflector will give little bit more gain.
The next step up the gain ladder might be a VDA or vertical dipole array and several recent expeditions have used these but usually in close proximity to the sea.
For a little bit of gain over a dipole (at optimum height) a quad loop will work well givibng about 2dB gain and does add the benefit of a considerable reduction in noise levels. Then of course if you want to go a bit further up the gain ladder you can add an additional element and you should benefit by about 7 dB over a dipole (and 2 dB over a 2 element yagi).
My first quad (photo) was a shortened quad for 17 metres. I didn't have space or height at the time for a full size one so made this when a utility pole in the garden became vacant. I based it on a design I seen for a small size 80m quad with both elements driven - hence the long stubs that also work as phasing lines. Tuning it was very hard work as I had to climb a ladder to adjust the feed point and I'd no antenna analyser then so had to go to the shack to see how it was looking.
Putting it up was good exercise - I had to carry the rotator uo the ladder, fix it and then carry up the assembled quad.
You'll note from the photo that I also grow good onions and tomatos and have a lovely xyl too!
