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Microwave Activities in Malta

Since the very early days of Radio, when a handful of dedicated radio amateurs, through their hard work and dedication, and under great duress from the very fact that Malta was a colony and these amateurs operated under strict guidelines from the authorities concerned and in some cases, one can say, were only tolerated rather than permitted, managed to advance this wonderful hobby ‘amateur radio’. The early days of AM radio, was the forerunner, and here great advances were made - it is enough to mention Professor TONNA BARTHET,whose contribution to Radio and radio amateurs could be described as a "GOLDMINE".

In radio technology, Robbie Galea established the first radio contacts on the Island, hence laying down the road to progress, it is well worth mentioning, that in those days, radio amateurs were not allowed to experiment as much as they would have liked to do, everything they did, had to be authorized, suffice to say that the use of the 2 metre band was acquired by sheer co-incidence, and by the intervention of a radio amateur, whose occupation was a dentist - the same goes for construction work, this was a taboo for the authorities, shortage of spare parts and components did not help either, however, in spite of all these difficulties, MARL and it’s members continued to grow in numbers and experiments . As time moved on, advances in radio techniques and the launching of more satellites, the availability of satellite dishes and the hard work and dedication by some radio amateurs, the use of high frequency transmissions appeared on the horizon.

MARL once again is in the forefront of these experiments as one can deduce from the following article, the idea is to encourage and inform other radio amateurs in the use of 10 GHz SSB and A.T.V. transmissions.

Around 1983, three very dedicated radio amateurs namely 9H1ES, 9H1GB AND 9H1FX carried out the first test transmissions, using Home Brew equipment, void of many test instruments and limited output power .e.g. 20 mill watts, wideband I.F. of 250khz and only using a mixer diode (IN23) and a Parabolic Antenna with a diameter of 45 cms and using a penny feed system.

It is relevant to add that these tests were carried out on a strictly ‘line of sight basis’

Other tests were made with other stations, e.g. Sicily, Sardinia Island IT9OSF AND IT9MHI.

Various difficulties were encountered with for example, temperature, humidity factors, but in spite of all this the group managed. A large number of contacts were managed during these difficult times, during morning, afternoons evening and night times.

In time, improvements were made by the introduction of:-

GUNN PLEXERS
MORE SENSITIVE I.F.’S (30MHZ)
A.F.C.

These improvements helped to extend the quality of the contacts, due to enhanced stability.

Larger antennas were also used to increase the (E.I.R.P) improvements were also noted in the contacts between stations in Lampedusa and Sardinia Island.

9H1ES in the 1980's

Construction

Around 1987, 9H1ES constructed a 10GHz transverter with an output power of 200 mwatts. For I.F. AN FT290 MK1 WAS USED - and contacts were made with I8 stations - SARDENIA AND SPAIN using 1metre parabolic dish using front fed horn system with a waveguide feed.

Two years later in 1989 due to personal situations and family bereavements, 9H1ES interest declined and all activity stopped completely.

Activity again picked up in 2002 by 9H1LO WHO introduced a system using all home brew equipment, and once again AT.V. Tests were once again carried out using a Modified ex TVRO LNB’S FOR TX and Rx.

Modified LNB’s were modified to allow transmission on 10.475GHZ. These were base band modulated and the output power was about 40 Mw - on the receive side, an ex TVRO analogue receiver and re-tuned LNB’S were used.

In June 2002, 9H1LO received the first pictures by co-incidence from an A.T.V. repeater in Ragusa JM75IA, Sicily.

9H1LO ATV
9H1LO Receiving Ragusa ATV Repeater

Malta Amateur Radio League showed a lot of interest in these tests and activities, and permission for the ATV mode was applied for and eventually obtained.

As 9H1LO had limited experience, he asked for assistance from 9H1ES, WHO HAD vast experience in Microwave Techniques.

This created and regenerated a lot of interest on the part of 9H1ES, and 9H1ES restarted building the required A.T.V. EQUIPMENT from scratch, although 9H1ES had 10GHZ transverter and Gunn plexers and associated materials i.e. WAVE GUIDES, WAVE GUIDE BANDS, DISHES.

For someone who was only equipped with SSB 10GHZ equipment, 9h1es had to build again from scratch a modified TVRO LNB WITH IF OF TVRO RCVR FROM 950 to 1700 MHZ with a local oscillator of 9.410 GHz.

After completing and building this equipment 9H1ES, TESTED FOR RECEPTION WITH RAGUSA REPEATER SIGNALS.

This resulted in good quality pictures, encouraged by this development, 9H1ES AND 9H1LO, combined all their efforts and equipment in order to establish communications.

It is a great pleasure for me to mention the assistance given by 9H1PF, who manufactured a slotted wave-guide antenna (16 SLOTS) 180 DEGREES BEAMWIDTH. This gave excellent results.

Marl once again, helped to create more interest in the subject, and has installed an ATV REPEATER installed in Mdina. It was built by 9H1LO and the antennas by 9H1ES and 9H1PF. Relevant information is as follows:-

TX 10.475 GHZ - RX 1.275 GHZ

9H1LO ATV
9H1LO & 9H1ES with the 9H1ATV Repater

10 GHz SSB TESTS

Another radio amateur involved in the 10 GHZ operation is 9H1BN, but had to relinquish his interest due to lack of operators and lack of activity in this mode. 9H1BN AND 9H1VW DISCUSSED the possibility of setting up equipment for this operation, 9H1VW ordered assembled and in some cases manufactured wave guides with the assistance of 9H1BN, together they tuned the equipment and more and more operators were encouraged and interested in the 10GHz SSB mode, 9H1LO modified a commercial data transceiver tuned to 10.368.200MHz.

9H1LO's setup consisted of:

200mw of rf power
60 cms off-set chaparral fed dish fed with 2 mtrs of very low loss cable (RG142)
IF. transceiver FT-290 mk1
9H1ES old equipment consisted of:
SSB electronica transverter
PW parabolic antenna with penny feed system - output power 200 mwatts
IF FT-290 mk2

9H1ES installed a beacon at his residence using modulated frequency shift keying fed into a wave guide from shack to roof area approx 15metres up and carried out tests on 10.368.900 to revive and regenerate his equipment, carried out tests between his home qth and selmun area approx a distance of 9 kms and another test from his qth to mellieha approx 11kms distance -it was here that 9h1es established the following based on his observations;-

Although there was no line of sight, contacts was established, this was remarkable, as every theory indicated that line of sight conditions must be present.

As the results obtained did not include line of sight conditions- 9h1es asked Marco 9h1bn to carry out further tests, because it was evident

That the case for line of sight conditions held no solid ground.

Test equipment was once again set up by 9H1ES and 9H1BN to prove that line of sight conditions was not mandatory

Mentioned earlier, 9H1LO completed building his equipment for 10 GHz and tested with 9h1es to establish, exact frequency off-set, a requirement, and had to be accurate.

9H1LO set up his test equipment at xemxija inside a hotel situated at sea level and was 6 stories high, 9H1ES set up similar test equipment at his QTH between these two operators, there was one large obstacle, Wardija Hill.

Once again, results from these tests showed poor results, signal levels were 3 by 3.

But contacts were successful - another attempt was made by 9H1LO at his QTH. Conditions were far from perfect, hazy, wx, 9H1LO decided to give it a go and test again from inside.His QTH overlooked Wardija Hill and his test equipment was located in the centre of the room, one window overlooking Wardija Hill. 9H1ES set up the same equipment but extended the length of the wave guide 3 metres above roof level, installed a 45 cm dish with a penny feed system. 9H1ES beacon was switched on to help 9H1LO locate signals from 9H1ES, a two metre operation (talkback) was also being used to make sure contact was not lost. after peaking the dishes orientation, 9H1ES immediately switched off the beacon and installed the transverter, but this time the output power was 20 watts resulting in satisfactory results with reports of 5/5 and 5/9 respectively - another proof that line of sight conditions is not mandatory. 9H1ES
9H1ES on 10GHz SSB

MARL members organized a field day coordinated and set up by 9h1es, using maps and coordinates were as follows:

9H1VW - Msida bridge
9H1BN - Paola
9H1LO - Lija (qth of 9h1sp)
9H1ES - Mellieha heights.

 

These four operator s established 4 way contacts at 1830 local time on the 18 th January 2004 - contact was continuous in spite of their individual dish orientation, contact remained static and solid.

These contacts again highlight the point, that line of sight communications is not the rule - these four operators did not have to set their dishes to a particular point - but on the contrary retained their dishes orientation and still managed to make the contacts. Yet, another test carried out between the coordinates of mosta and naxxar, with 9H1VW and 9H1ES, with 9H1VW dish pointing towards a windmill and 9h1es was totally dwarfed by a school, again proving the point once again, that of no line of sight comms. Reports of 5/9 both ways obtained.

9H1LO 10GHz
9H1LO on 10GHz SSB

The test to end all tests :

On the 31 st January 2004, a test to end all tests took place between 9h1es , 9h1lo and 9h1vw located at two different points and coordinates.

The day was nice with 50 percent humidity and no wind present, both operators set up talkback on 2 metres via R4 repeater, initially the tests proved negative and no contact was made, 9h1es decided to replace his 48 cm dish with a one metre dish in order to increase the gain, again negative results -orientatation checks made to no avail -9H1ES increased power by applying a twt delivering 20 watts power output into a one metre dish, on switching on, 9H1ES was heard by 9H1VW, located at some point at delimara tower, 9H1ES then peaked his dish and quickly informed 9H1VW that he was rcvng 9H1VW with a shift difference of 71KHz, it was then very clear to all concerned that the reasons for no contacts was because of the shift difference involved namely 71KHz in fact 9H1ES removed the twt used only 200 mw power with the same one metre dish, changed to SSB mode and communication was established with very good results of 5/5 all round - 9H1LO joined the group running these tests and established communications both with 9H1ES and 9H1VW.
9H1VW
9H1VW on 10GHz SSB

Conclusion

The article has been written with one thing in mind, to encourage radio amateurs to get interested in this mode of communication, it is a unique form of contact, gives enormous satisfaction to all those that want to get involved in constructing or building or installing their home brew equipment, should they try to get involved, they will find assistance and experience of operators who have personally tried, tested, built, modified and improved equipment,and marl is looking forward with pride and satisfaction, to the day, not in the far distant future, when 10GHz SSB operation becomes what the 2 metre operation was a few years ago.