GB2AES – 8th April 2015 – Admiralty Experimental Station

GB2AES remembers a very significant radar sighting by Admiralty Experimental Station 1 at Sumburgh Head, Shetland, on 8th April 1940, which gave early warning of a planned attack on the British Home Fleet at Scapa Flow Orkney. GB3AES will operator for one day only on the 75th anniversary of this sighting.

The Sumburgh Head radar facility started permanent watch on 27th December 1939.  The station was tasked with plotting surfaced U-boats attempting to escape from the North Sea into the North Atlantic, but was also capable of detecting aircraft.  As the science and practice of radar evolved through the late 1930’s, Sir James Somerville, Vice Admiral of the Royal Navy, proposed a wider network of naval stations to protect the strategically significant waters to the north of Scotland.  This included stations at Dunnet Head, South Ronaldsay, Fair Isle, Unst, and later, on the north-west coast of Iceland.

Construction of the Sumburgh Head radar station began in October 1939. The receiver hut was placed just outside the southern wall of the inner enclosure of the Sumburgh Head Lighthouse buildings, whilst the transmitter hut was erected immediately adjacent to the foghorn.  Both structures still survive, with the transmitter hut having been restored to re-create how it might have appeared in 1940 – with a little bit of artistic licence. Having both transmitter and recieving stations in one building allows visitors to see the complete operation.

The original huts were made of wood but were soon replaced with a more substantial shuttered concrete design.  The huts were straddled by gantries which carried the aerial arrays, one for transmitting, the other receiving.  Inverted searchlight turntables were used for rotation, which was carried out manually using a chain connected to an up-turned bicycle framework – with the pedals replaced by wooden handles for turning!  This set-up can be seen in the re-created radar hut.

Links

Sensitivity of Icom IC7100 on 6 & 4

On the Icom IC7100 Yahoo Group the question has been asked as to whether the very versatile ICOM IC7100 might be a little bit deaf on 4 metres.

Picture of the ICOM IC7100 Transceiver

ICOM IC7100 Transceiver

Mark G0MGX made some investigation into this suggestion which resulted in the graph below –

Results of investigations into sensitivity of IC7100 on 6m and 4m

Results of investigations into sensitivity of IC7100 on 6m and 4m

Mark then went on to compare the IC7100 with a Kenwood TS990 by measurement of the TS990 sensitivity on 6 metres, as shown on the following graoh –

Measurement of TS990 sensitivity on 6m

Measurement of TS990 sensitivity on 6m

The person who originally posted the question made the observation that the IC7100 reception on 4 metres appeared to benefit from the insertion of a pre-amplifier.

Links

YP10EURAO: 10 years of EURAO

From February 2 to September 31 2015, the special callsign YP10EURAO will be aired, mainly at weekends, to celebrate the 10th anniversary of the formation of the European Radio Amateurs’ Organisation EURAO.

YP10EURAO is put on air by the  Asociatia Radioclubul României, YO9KYO, a associate member society of EURAO.

Links

Comparison of Digital Voice Systems

The Charlotte North Carolina Digital Radio Group runs Digital Voice repeater systems. They don’t pick favorites – they’re putting them all up (or, at least, most of them).
Their D-STAR system is older and more evolved (multiple sites on 144, 440 and 1200), but they’ve added DMR/MotoTRBO in a big way, and recently installed one of the Yaesu C4FM “Fusion” repeaters (though they’re not “fusing” it – they run it digital only). They’ve got an NXDN repeater on the bench. Only P-25 is missing.
Most of us were probably already confused by the availability of D-Star, DMR and Fusion, but this video introduces us to NXDC and P25 and starts to give us some comparisons between the systems.

In this talk from the Charlotte Hamfest, Roland Kraatz W9HPX presents the research he’s done on D-STAR, DMR and Fusion. No on-the-air comparisons  This is a slide show that compares operational capability and some tech specs.

We’re a few weeks away from Yaesu’s North America release of WIRES-X, the Internet linking system for Fusion, so Roland only has a few details on that based on manuals.

Here are links to some of the resources Roland talks about:

http://charlottedstar.org/ – The Charlotte Digital Radio Groups site

http://charlottedstar.org/Comparison%… – Roland’s slide show PDF

http://www.trinityos.com/HAM/Yaesu-Sy… – KI4ZD’s slide show on Fusion