Until recently, the only recorded activity in the UK on 47GHz was the tests between G3HBR and G3HBW. They used 50mW MA Gunns and home-made circulators. The best DX worked was 13km.
There has been much more activity on 47GHz in the last few years. Mostly this has been wideband FM, centered around 47.1GHz, but there is increasing interest now in narrowband cw and ssb, on 47088 MHz.
G4KNZ, G8KMH, G3FYX and GW3PPF are all using surplus MA-86147 49GHz Gunn oscillators originally from 4GHz parametric amplifiers which were pumped at 49GHz. The oscillators initially were set to 49GHz, with a nominal 100mW output, and they can be pulled down to 47GHz. A 15dB cross coupler provided with the Gunn is used to couple power into a receive mixer. A detector mount also provided with the equipment can be used, but the original diode, designed for power levelling at the 3mW level is very insensitive and needs replacing.
The picture
right shows Lehane G8KMH with his wideband FM equipment using this
type of surplus equipment at Martlesham on the 9th November 1997. Two 27dBi
horn antennas are used, which avoids the need for any transmit-receive
change-over, and if the other station is also using a similar 2-antenna system,
allows full duplex operation. So far, Lehane has worked 25km using this
Nominal operating frequency used is 47.088MHz (i.e. the designated narrowband segment), calibrated either by listening to the 20th harmonic of a DDK004 2.354GHz multiplier or the 2nd harmonic of a 24GHz Gunn tuned to 23.544GHz.
Stations who have had at least one contact using this type of wideband equipment are: G0JMI, G3FYX, GW3PPF, G4KNZ, and G8KMH. Recently, three more stations - G3PHO, G8AGN, and G0CZD - have obtained the surplus 49GHz Gunn equipment, and are busy getting operational.
Other stations who have also had at least one wideband contact are G3LQR (using DB6NT narrowband, with a wideband IF) and G4DDK.
G4DDK has modified an NEC Pasolink equipment for 47GHz work - this equipment is normally used to provide a duplex 2MB/s link in the 50GHz comms band. A 12.5GHz DRO provides drive to a waveguide mounted varactor diode quadrupler. Transmitter output is 10 to 15mW. A small amount of transmit is allowed to leak through to a waveguide mounted mixer diode, to provide a receive LO.
Longer term, there is more interest in getting operational using narrowband - this is especially of interest to those near the East Coast of England, looking for tests across to Belgium and The Netherlands, where any operation will undoubtedly be narrowband. For some years, there was scepticism in some quarters that the North Sea would be spanned on 24GHz - this has now been done a number of times - and as equipment improves, and the number of active stations increases, this will become a more regular occurrence. G4KNZ believes it is only a matter of time before 47GHz spans the North Sea.
So, most of these stations, and several others, are now building narrowband gear. Stations with equipment already built include G0FDZ, G3LQR and G3PYB, with G4DDK also expected to be ready soon. G3FYX and G4KNZ are also building.
The 13km record set by G3HBR and G3HBW was extended to 25km by G4KMZ and G8KMH in August 1995, then to 39km by G4DDK and G4KNZ in July 1996, and to 41km by G3FYX and G4KNZ in December 1996. Finally, in October 1997, the distance was extended to 65km by G3FYX and G4KNZ again.
From the Dubus lists, the first QSO recorded was on 3/Oct/84, between HB9MIN and HB9AMH over a distance of 1km. The current record stands at 166km, between HB9MIN/p and HB9MIO/P.
Other stations operational (with their best DX) are: DF2CA (15km), DB6NT (94km), DK4GD (80km), DF6VB (69km) and DC0DA (69km).
All the European activity is believed to be using narrowband equipment.
There is less reported activity in the US. The US record is listed as 105km between K7AUO/7 and WA3RMX/7. More information would be welcome, if anyone has any!
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