Postscript to Activity Report of Tuesday 24th Nov – re: VK9XX

The German expedition station VK9XX on Christmas Island far away in the Indian Ocean has still been putting out consistently good signals into the UK on 40m all this week. Some days as early as 14-00UTC they were audible on SSB at readability 3 and S3 on 7045khz with QRM. Signal strength went up during the day peaking at RST 579/589 on CW by 22-00 UTC accompanied by a huge pack of stations mainly calling HF of them as instructed by the VK operator who was clearly calling “CQ UP”. Unfortunately the operating discipline of far too many of the EU stations was very poor with people often calling directly on the DX station’s frequency rather than several khz HF of them. They were also ignoring the DX operator’s requests for “CQ SA/NA only” – i.e. replies wanted from South America or North America only. I must say that I did not hear any G stations breaking the CW operating etiquette. The operating standard by VK9XX was absolutely first class

The golden rule is always to listen first to find out what is happening before transmitting then use the TX clarifier or second VFO to operate split frequency. It is not always easy to pick out the DX operator’s frequency through the QRM. Tuning gradually LF of the pile-up is one way, the other is calling up reports on the DX cluster via Ham Radio Delux on the internet.

Yesterday during the late afternoon (Tuesday 24^th), VK9XX was down as low as 7001khz right at the band edge but previously he was up around 7009/7010khz. The expedition will be active until December 5^th. . There had been no postings so far today on the DX cluster by

15-00 UTC but take a listen !

73, de Derek Atter , G3GRO

Activity Report – Derek G3GRO

From time to time I have been active on various bands during past month mainly on 80m and 40m but with occasional forays on 14Mhz and 18Mhz and briefly on top band mainly using the 136ft Windom antenna which seems to get out reasonably well despite the fact that it slopes down rapidly to the South away from the house down almost to ground level. I have not yet managed to get the halyard far end hauled up into the 50ft oak tree at the bottom of the garden. The temporary 240ft rectangular loop running mainly on the top of the fence continues to give a good account of itself on 80m on short skip due to its significantly lower noise level during the recent very noisy conditions on that band.

40m has been open to VK during the day sometimes. I heard a VK6 at lunchtime during the Sweepstakes” contest on Sunday 8^th November up at the Club using the new StepIR beam and could also even hear some USA stations very faintly on that band calling CQ “SS” on CW which was surprising during the day on 40m. By mid-evening US stations were by then coming through quite strongly on 40m at home on the Windom antenna and I worked in quick succession N1KF on CW with 589 reports both ways and K1LT with 599 reports.

Later in the week at mid-day on 16^th November I worked an unusual one on 20m in the shape of OX/EA4NA in Greenland again with 599 reports. One however that “got away” later in the evening was W3ZU in Florida heard at 58 on SSB on 7134 khz with a pile up and the best I could manage through the “crud” was a QRZ?

Today (Sunday 22^nd Nov.) again on 40m I heard VK4HFO at 1500 UTC calling CQ on CW at only about RST339 who then worked PC5A giving him RST559. Later at 1745hrs I heard VK9XX on Christmas Island in the Indian Ocean at a solid RST579 for at least 30 minutes working EU stations in a monster pile-up on 7010khz working split frequency. Despite my calling him on 400W many times I did not manage to get through the EU racket spreading over 2 to at least 7khz HF.

Radar History – A Proposed Re-enactment of the Historic “Daventry Experiment

Derek G3GRO reports a recent interesting QSO with Giles G0NXA during an 80m net during which Giles described the existence of a very interesting and ambitious plan to mark the anniversary in 2010 of the historic “Daventry 4roriginally carried out on 26^th of February 1935 by Robert Watson Watt and his technical assistant which in effect marked the birth of the development of radar in the UK which was to play such a vital role in the outcome of World War2.

In the original experiment , the signal from a BBC transmitter at Daventry on HF was used to confirm the presence of an overflying Hayford bomber by detecting reflections from the aircraft thus confirming the basic feasibility of a defence against potential enemy aircraft by a technique which was later to be called RADAR

The proposed modern re-enactment which will take place between 1200hrs and 1400hrs local on 26^th February 2010 will involve a flight of 24 private aircraft at 5 minute intervals flying at an altitude depending on the weather of between 2000ft and 4000ft along the original track followed by the Hayford bomber from Borough Hill to Towcester racecourse in Northants. The availability of the aircraft has been arranged by and will be co-ordinated by Giles G0NXA who is himself a pilot and who has already obtained initial agreement in principle from the local Air Traffic Control centres likely to be involved.

A more detailed formal plan is currently being prepared by Giles. The test signals and ground recording equipment are being provided by two local radio clubs. Information on the proposed test frequency and the clubs involved was not given during the QSO. It is a very ambitious plan and it is to be hoped that it will succeed. No doubt that more information will be available later in the columns of Radcom .

73 de, Derek G3GRO.

Tunnel Diodes

Whilst on a theme of components, Roger G3XBM, pointed GQRP readers to an article by Ramon Vargas Patron called Oscillations and Regenerative Amplification using Negative Resistance Devices. He uses a lambda diode arrangement in place of a tunnel diode. His lambda diode is made from and an MPF102 and a 2N3820. The article shows how these can be used to make a sine wave oscillator and a simple AM receiver.

Stewart/G3YSX

A Primer on PIN diodes

Bob, G3OOU posted an interesting link to the GQRP list a few days ago - a primer on PIN diodes. This was produced by Microsem,i who puchased Unitrode. Unitrode are firm that was very famous for the manufacturer of PIN diodes and who produced a classic reference book on the subject.

If anyone is interested in experimenting with PIN diodes, you can use some types or ordinary power rectifier such as an 1N4007 in PIN diode mode. There is an instructive thread here on the subject which points to an ARRL article by W7ZOI which uses a 1N4007 as an attenuator in the IF amplifier of his spectrum analyser (see fig 5).

Stewart/G3YSX

El Silbo

El Silbo is a fun idea by AA1TJ. It is a voice powered DSB radio transmitter. The audio picked up by the microphone serves both to power and to modulate the transmitter.

Stewart/G3YSX