New UK 10 GHz Distance Record

From http://www.southgatearc.org/news/july2006/10ghz_distance_record.htm

New 10GHz UK Distance Record

Ian Lamb G8KQW's achievement in establishing communications at 10 GHz over a distance of nearly 1,400 km using a transmitter power of just 2 watts illustrates that transmissions on 10 GHz are not just confined to national borders. What one administration does at these frequencies can have an impact right across Europe.

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New 10GHz UK Distance Record

Late last week I had been looking at the “Hepburn Tropo Index” which was forecasting strong tropo ducting from UK to Europe on Saturday 15th July.

Looking at the ON4KST microwave chat (KST) on Saturday 15th I noticed that stations in IO93 (e.g. G0EWN) were experiencing well above average propagation on 10GHz into ON, DL and SM compared to the south and south east of England.

Early on Saturday evening conditions on 144 and 432MHz were rapidly improving at my QTH in IO91 and I was working OK, OZ and SM on these bands but hearing nothing on 1296MHz or higher.

By midnight I was working OZ and SM on 1296MHz at 59 both ways (65W + 35el) and I concluded (and hoped and prayed) that the propagation was moving southerly due to these improving conditions on VHF / UHF. I decided to sleep and rise early on Sunday in the hope that the ducting had moved far south enough for me to take advantage of working 1296MHz and 10GHz.

I woke at 5h30 on Sunday (16th July) morning and on checking KST found that G4EAT had worked SM4DHN on 10GHz, my heart sank because my immediate thought was that the duct had become coastal and, as normal, wouldn’t be workable from several hundred kilometres inland.

A quick tune around the bands ensued and the Emley Moor beacons on 432 and 1296MHz were end stop (and more).
The Martlesham 1296MHz beacon was 10dB up on normal (nothing received on 10GHz) so there was clearly very enhanced propagation over land plus a seemingly strong northerly duct. No SM or LA beacons could be heard.

At 6h20 I asked Lars-Bertil SM4DHN to test on 1296.210MHz via KST and was amazed to find his signals 59+ same as the Emley Moor beacon. We QSY’d to 10368.200 and worked very easily on CW with no repeat information at 539 – 559.

This was an unbelievable contact for me, not only because of the sheer distance involved at 1347km but also because both Lars-Bertil and I are located several hundred kilometres inland at either end of the path.

I then worked other coastal SM stations that were logged into KST
· SM6AFV 59+ on 1296MHz and 559 – 549 on 10GHz at 1192km
· SM6HYG 59+ on 1296MHz and 559 – 559 on 10GHz at 1118km

At 7h30 I worked SM6VTZ on 1296 at 559 – 559 but signals dropped during the QSO. By 07h40 all beacons on all bands were at normal strengths.

Throughout this one hour ten minutes of madness John Wood G4EAT was spotting SM4DHN’s exact 1296MHz frequency for other stations in IO91 but sadly none of them were able to hear his signal.

Looking at the radio sonde data over Nottingham at midnight last Saturday it is clear that there was an elevated duct at 1300m, possibly a lower duct at 750m in addition to some ‘subsiding high’ lift conditions.

The radio sonde data over Schleswig (near the German / Danish border and pretty much mid path) at midnight shows a surface duct and an elevated duct at the same time.

The Emley Moor beacon antennas are ~ 600m amsl and it could be that they were coupling directly into one of these ducts being the same duct as I was coupling into thus explaining the extraordinary received signal strength of GB3MLE on 1296MHz.

I may also have been able to couple into the duct more easily than other stations because I was using a relatively small dish with a larger aperture than is commonly used nowadays.

I hope to understand this particular occurrence further, maybe there is a propagation expert lurking who is interested to interpret / provide further data to try and explain exactly what occurred?

This was a very thought provoking event.

These contacts were all made with my second 10GHz system which comprises IC271E + Mutek, DB6NT transverter + DB6NT 2W SSPA and a Procom fed 48cm dish at 14m above ground.

This system is usually used portable on a small tripod for alignment of antennas before 24GHz contacts but is presently installed on my home station mast whilst I am modifying my regular dual-band 6/3cms transverter.

Conclusion - right place at the right time!

Ian Lamb G8KQW
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73 Trevor M5AKA
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