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34nd Dorsten GHz-Convention

It was with a great deal of relief that the conference chairman, Peter Hörig, DL4BBU, was able to inform delegates that once again a full programme could be presented. Fortunately, therefore, the dearth of papers at the 2010 conference appears to have been an aberration.

As always, the conference was organised by the DARC chapter Herrlichkeit Lembeck, N38, in collaboration with the DARC district N and the VHS Dorsten.

Immediately following the introduction of delegates and a brief welcoming speech by the VUS advisor to the DARC, Jochen Berns, DL1YBL, Martin Henz , DL5NAH, DARC advisor VHF Radiosport, proceeded to the long-awaited awards in the three categories of the VHF Contest Cup, accompanied by the statistics of the just-ended contest period. It is worthy of note that Martin had commissioned a complete redesign of the Cup as an incentive for ever greater efforts in the pursuit of the trophy.

Opening the presentations is a tradition with Jürgen Dahms, DC0DA, as he is routinely the first contributor to submit his papers. In this session he shared his 'Operating Experience Above 100 GHz', specifically in the 122 GHz band. In addition to advising on the selection of suitable diodes and the improvement of mixer circuits, he illuminated the ins and outs of the appropriate operating procedure. In concluding his talk he complemented theory with a short video showing an SSB contact between OE5VRL and OE5WOG over an incredible 55km distance.

Martin Henz, DL5NAH, added to his customary contest statistics by analysing ways to improve contest stations without increasing technical complexity. He demonstrated the improvements achievable using his statistics of selected contest stations.

Ralf Wehling, DF6VW, reported on the integration of a Perseus SDR receiver into a microwave contest station for 10 GHz and 24 GHz. He correctly pointed out that it was time to replace 40 year old analogue IF equipment with more modern technology. The use of SDR expands the scope not only in the shortwave bands as there already is available a host of commercial and non-commercial hardware that is suitable for microwave amateurs. Apart from the Perseus, there are the Lima-SDR and the FunCube-SDR. Ralf demonstrated the clear superiority of SDR based IF systems over analogue equipment using visual representations and off-air recordings of signals from the 'hurly burly' of contest activity and rain scatter operation.

The lunch break provided an opportunity for 'eye ball' QSOs and performance measurements on home brew equipment, courtesy of DK2FD and his crew, DF9IC and DG6OBE who made available their test equipment. Comprehensive test facilities are finally again available to delegates as was customary during the 80's which will make the conference all the more attractive.

After the lunch break a presentation by Markus Heller, DL8RDS, provided further insights into the advance of SDR in digital signal processing on the basis of USRP2. This US made equipment, that is already suitable for use as a transmitter and receiver, enables the implementation of amplifiers, mixers, filters, oscillators and so on with the aid of software. One almost felt like watching a science fiction film as Martin built in near real time a receiver simply by selecting modules from a software library and assembling the same without any solder smoke. It was latest at that stage that any analogue-loving microwave aficionado realized that the march of SDR can no longer be halted. However, it may be consolation to some that digital technology does not (at least not yet) deliver significant power levels.

Dirk Fischer, DK2FD, returned delegates to the analogue world with his talk on solid state SHF power amplifiers, which is not to say that he presented old-fashioned technology. On the contrary, the rapid technological advances are making low-cost high power transistors available even to amateurs. A single transistor is now capable of producing more than 100 watts of power in the 23cm and 13 cm bands and unlike tubes, transistors are easier to parallel to increase output. Already there is experience in the amateur radio field of how to design and build high-power amplifiers for the microwave bands featuring up to 16 transistors. Set against these positive developments is the issue of how to adequately cool such power devices. Dirk showed water cooling to be the most effective route, maintaining that this approach is only marginally more complex than a more conventional solution.

Wolf-Henning Rech, DF9IC, provided a most interesting 'lesson' with his paper on 'Investigations into Noise Sources'. He impressively presented this dry topic both theoretically and with practical applications. Based on his theoretical treatment of the subject he introduced two homebrew noise sources that, using rather mundane zener diodes and small-signal transistors, enable noise figure measurements up to 6 GHz and whose performance is on a par with commercial equipment.

In his second talk he reported on an active project of the contest group DR9DA, which he qualified as the first stage of an undertaking to build a mast mounted power amplifier for 23cm. The project aim is to fit the preamplifier, power measurement module and the final stage into a onetime UMTS cabinet. Henning's approach to meet this statement of requirements was fascinating as, due to space restriction, he was unable to use commercial modules. He gave a detailed description of the already completed individual modules. The final amplifier employing eight MRF286 and targeting a power output of some 400 watts is clearly capable of meeting even commercial requirements.

Management of the amplifier would be by a universal telemetry/telecontrol unit whose development was explained by the final presenter and member of the DR9DA contest Group, Alexander Kurpiers, DL8AAU. In his presentation, Alexander developed the statement of requirements for the control system and subsequently translated this into a final digital design. The limited scope for effecting repairs to the system during contests adds further complexity in that easy replacement of components at the input and output circuitry precludes the use of SMD components and calls for socketed DIL ICs instead.

During the concluding discussions, as always moderated by Peter Raichle, DJ6XV, delegates applauded the diversity of the conference topics, in particular the inclusion of SDR technology , and the commitment of the presenters. It was generally felt that the quality of the conference had, therefore, recovered to the high level seen in the past.

Delegates also specially welcomed the further expansion of facilities for the testing of equipment and modules which aids the revival of one of the mainstays of the conference.

Participants were invited to forward any photos taken at the conference to web master Ralf Benninghoff, DG6EA, hoping that their presentation on the conference web site will give those unable to attend in person an impression of the event.

As in the past, the proceedings can be ordered for € 8.00 (order details on the homepage www.ghz-tagung.de) which also provides a complete listing of all available proceedings of past conferences.

Henrich Frerichs, DC6CF, who miraculously has not missed a single conference, has again produced a video that can be ordered directly through him.

Remark: The corresponding pictures you'll find in the German version on the website under 'Rückblick/2011/Bilder'.

Peter, DL4BBU

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last Update: 09-07-2010