In 1970 Costas Tzezairlidis SV4CG built a unique electro mechanical machine using two motors to achieve horizontal and vertical scanning.He had found a motor which rotated at 960 R.P.M.which corresponds to 16 revolutions per second, the exact speed required for the horizontal scanning.The speed of the second motor was 1 revolution per second.The reciprocal motion was produced by a cam through an 8:1 reduction gear.A weight attached to the microscope pulled it back to start the next line.The microscope was focussed sharply on the drum carrying the picture to be transmitted.Resolution was excellent.
The `microscope' consisted of a cardboard tube with a 13 cm focal length lens at one end and a Philips OAP12 photo-diode at the other with another lens in front of it.This primitive microscope produced a picture of reasonable quality.
For reception SV4CG made a converter using the long persistence P7c.r.t.With this set-up Costas had his first SSTV contact on 40 metres with SV1AB on February 28th 1971.After that he had many contacts on 7 and14 MHz as can be seen from the extract from his log.(The special commemorative prefix of SZ0 was used by all SV stations during 1971).
6.Costas Georgiou SV1OE.(E.M.E.)
Up to the end of 1988 the only Greek amateur who had positively authenticated Moonbounce contacts was Costas Georgiou SV1OE.His very first contact was made in 1982 when he contacted VE7BQH in Canada on 2 metres.In the ensuing four years Costas managed to work four more stations: K1WHS, SM4GVF, W5UN and KB8RQ.
In 1982 Costas had been trying for three years, without success, to hear his own signal via Moonbounce.The reason for his failure was that he was unaware of a very basic fact.
"I was completely ignorant of the Doppler shift effect", Costas told me."The frequency of received signals varies according to the position of the moon.If it is to the East of your own location the signals return 500 to 1,000 Hz below the original transmitted frequency.For years I had been sending long dashes slowly and waiting to hear my signals return on the same spot, which they never did.This happens for one instant only, when the Moon is at 180 degrees azimuth, exactly due south.When it moves to the west of south the returning frequency is correspondingly higher.Using a 50Hz audio filter (which is essential for Moonbounce) it is very easy to miss the weak signals.Soon after I found out my ridiculous mistake I began to hear my signals, naturally with a delay of one or two seconds because of the enormous distance involved -- 770,000 kilometres, 385,000 there and 385,000 back.
Costas continued: "My next problem was finding the moon.I had no computer at the time and no Keplerian elements.I mounted a small video camera in the centre of four 16-element Yagi antennas and rotated the elevation and azimuth motors until I could see the moon in the centre of the monitor in the shack.Of course when the sky was overcast I was out of business.Much later when I obtained a little Sinclair ZX80 computer life became easier.
"When I made my first contact I was simultaneously in QSO with SV1AB and SV1IO on 1,296 MHz who could hear what was going on.I remember SV1AB got very excited and began shouting `I can hear him, I can hear him!' The QSO was with VE7BQH.Later Lionel sent me a very valuable present, valuable not for its cost but for the fact that it was something quite unobtainable in Greece at that time -- a very low-noisepreamplifier for 2 metres.
"After the successful launch of Oscar 10 those amateurs who had complex antenna systems and low-noise receivers they had used for Moonbounce congregated on 145.950 and spoke to each other on QRP which prevented ordinary mortals from hearing them.By QRP I mean outputs of half a watt or less.But when finally one day I broke into a net QSO I arranged schedules for Moonbounce with two stations in Sweden.I had a successful contact with one of them but never heard the other.The reason may have been a very simple one: the polarisation of signals returning from the Moon varies from one moment to the other, so if you have been transmitting with horizontal polarisation and go over to reception it is very easy to miss the answer of the other station if the polarisation has changed."SV1OE then explained the very strict procedure which must be adhered to for Moonbounce schedules.
"Schedules are arranged to last one hour.The first station to start transmitting on the hour must be the one whose QTH lies to the east of the other.The calling frequency for Moonbounce is 144.011 MHz., and the duration of the call is 2 minutes, but for the first minute and a half you call CQ DE SV1OE and during the last half minute you also give the call of the station you are trying to contact, for instance G3FNJ DE SV1OE.You must on no account transmit for more than two minutes because at the beginning of the third minute the other station will begin transmitting the same pattern of signals.But if he has heard you he will alter the pattern.For the first half minute he will send SV1OE DE G3FNJ and for the ensuing minute and a half he will transmit the letter O which signifies that he has heard your callsign completely and without difficulty i.e.Q5 in the Q Code.If I have also heard your callsign completely I will send G3FNJ for half a minute followed by RO for a minute and a half, which means that I have also received your callsign and your O.And you will reply RO 73 which concludes the successful contact.
"There are one or two other letters that can be used.Sending M signifies that I hear you well but can only copy 50% of your transmission, equivalent to Q3.And the letter T signifies I hear you but cannot read youat all - Q1.
"It has been found by experience that the best sending speed is 8w.p.m.Sending slowly or very fast presents problems at the other end."
