Satgen 114 Exploring the Microwave Satellites by GM4IHJ 3rd June 91 Have been asked several questions about the sorts of rigs necessary to explore amongst the microwave satellites , 900 MHz to 13 GHz,mentioned in the RSGB Space Radio Handbook.There are 3 essentials. A dish of about 1 metre diameter or bigger which can be polar mounted ie on a fixed base but rotatable to cover the geostationary arc as seen from UK. The dish to have a variety of exchangeable feed horns suitable to the frequencies required. The dish can be outdoors and need not be high up, or it can be indoors provided it looks south through one thickness only of good non metalised glass ( not double glazed) in a window preferably 6ft high and 10 ft wide . Alternately indoor or outdoor dishes need not be fixed. They can be on a sturdy trolley moved in azimuth, on indoor plywood boarding or outdoor smooth flags/tarmac, and in elevation, on a turnbuckle or support wedge. The second essential is one or more LNBs Low Noise Block mixers which take the microwave signal and convert it down in most cases to 900 to 1750 MHz. LNBs need power supply fed up the receive coax and they require the small F type plugs. In some cases the LNB and the feedhorn come as a set , and, rotation of polarisation is provided either by a motor or, by a magnetic insert. Circular polarisation can be achieved by using Teflon inserts in the feedhorn waveguide. The signal from the LNB usually goes to a push button 20 channel intermediate TV receiver which also carries the polarisation control. But this is awkward to use for general studies and experimental work. It is therefore common practise to fit a 2 way splitter in the LNB signal downlead. One port of the splitter can feed the commercial TV unit while the other port feeds a receiver capable of tuning 900 to 2000 MHz. Several receivers such as the R7000 from ICOM cover this range with SSB and wide and narrow band FM. This SSB detector is very useful for finding weak signals and for doppler or spectrum analysis, but if you are stuck with an FM receiver do not despair , it can be used if you accept its limitations. For microwave signals below 2500 MHz an LNB is not required . Suitable feedhorn designs are to be found in the RSGB VHF Handbook EG in 3rd Edit Fig 8.125, and cheap in line pre amplifiers broadband 900 to 1750 MHz are available from sat TV suppliers. For 2.4 GHz signals good converters are available via Piper communications if you want to try for Oscar 13, Dove, or Oscar 16. Oscar 16 has special experiment days which are good fun. For signals on higher frequencies surplus LNBs and feedhorns are available at rallies, and if they are cheap enough there is no expensive risk in shifting their frequency coverage Weather protection is important . This writer has 2 dishes which are used indoors in winter but one goes out each summer for experiments on the Soviet Molniya elliptical orbiters at high elevation northward over the Pole with their microwave Mir and Buran links. 73 de John GM4IHJ @ GB7SAN