Satgen244 Satellite Antennas Part 1 by GM4IHJ 27th Nov 93 BID of this msg is SGEN244 Please use this BID is you retransmit the msg Looking at the possibilities for HF Satellite antennas which can be used to listen to RS10 and transmit/receive to and from RS12 , soon convinces the experimenter that there is no such thing as a perfect antenna. At GM4IHJ the following have been comparison tested - Long Wire, Vertical with counter poise, Sloped dipole , Horizontal dipole , Crossed dipole and, 3 element Yagi beam. They all work - more or less, so it depends on what the user can afford and fit. The Long wire is cheap and easy to install but it is highly directional and can miss a great deal unless you finish up as I did pointing it at the pole from where I get most DX. The Vertical with or without a counterpoise is much less effective, its high angle of take off is simply the opposite of what you want for satellites. It works best when the sat is overhead , where you need least gain because the sat is very close to you. By contrast it is least effective at low elevation when you want max gain to catch the weak DX on your horizon. Many Amateur Radio handbooks flatter the vertical by showing graphics of the ionosphere which are hopelessly out of scale . One RSGB classic shows the ionosphere around 3000 kms high instead of its true 300 km. This sort of nonesense makes any antenna look good. The dipoles are much better. A crossed dipole was perfect in 1976 for Oscar 6, but a noisy micro computer came to live next door in 1985 , so its lack of directivity became a problem rather than an asset. So since then it has given way to a sloped dipole on the chimney as far away as possible from the offending QRM. The sloped dipole being preferred to a horizontal dipole because of its all round view. But for the real DX on the horizon there is nothing to beat a 3 element beam, if you can afford it and have somewhere nice and high to mount it . Even without a rotator, fixed pointing north for most of my polar DX it gets more signal and less QRM, covering the Arctic from about 330 to 030 azimuth, with if necessary the possibility to switch to the sloped dipole for other bearings outside this arc. With the beams high gain you get enough signal to follow your favourite satellite through the regular fades and dips in signal strength due to Faraday rotation. Although Faraday at 10m is much faster than at 2m ( maybe 16 to 20 fades per orbit pass horizon to horizon as opposed to 3 or 4 much longer more annoying fades on 2m ). But having said all that if you can put your beam up on a tower and control its rotation through 360 degrees you probably have the nearest to a perfect answer you are likely to get - unless you are like IHJ who in the excitement of chasing DX often forgets to move the beam. At which point a switch over to the sloped dipole usually relocates the sat , and also provides a handy feature when satellites appear from bearings which are nowhere near the anticipated Great Circle path. Do not forget the Geminids 13th and 14th December . A good shower to my north east and east during the evenings with if you can stand the cold out doors, some good visual tracks which for this shower seem to move quite slowly, with sometimes the odd very bright slow fireball. 73 de GM4IHJ @ GB7SAN