32nd Dorsten GHz-Convention

On 14 February 2009 some 170 enthusiasts from Germany, Belgium, The Netherlands and Switzerland convened in Dorsten for the annual Gigahertz Convention.

Participants will remember this particular gathering for some time to come as the convention's organiser, Peter Hoerig, DL4BBU, announced during his opening talk that the organisers had been 'flooded' with an unprecedented number of papers to be presented. No fewer than 10 OMs had responded to the call for papers, which bears witness either to the continuing interest in the convention and/or attests to the success of the organisers' persistent goading. This had made it necessary to impose a strict time management regime on the speakers to enable all papers to be presented in the course of the day.

As in previous years awards were presented to the winners in the three categories of the DARC VHF Contest. The number of logs submitted had continued to grow for the second year running, reaching a noteworthy total of 5080!

Before commencement of the presentations of technical papers, Jochen Berns, DL1YBL, head of the DARC's VHF department confronted delegates with shocking news concerning the 24 GHz-band. Owing to the worldwide financial crisis (this crisis apparently now serves as blanket alibi for all sorts of things - good and bad! Ed.) automobile manufacturers, for economic reasons, wish to abandon the frequency band of 74 - 79 GHz for automotive applications, such as vehicle radar, and are seeking an ultra-wideband allocation in the 24 GHz band instead (the EU Commission has meanwhile granted the 24 GHz allocation. Interesting background information can e found here: http://www.heise.de/english/newsticker/news/55351. It speaks for itself! Ed.)

The DARC was said to have been made aware of this development late in the day with barely a week to file its comments on the proposals. Fortunately, the RSGB had already submitted a response which the DARC was able to support. The general view was that such a wideband allocation would likely not impinge significantly on amateur radio activities due to the limited range of such radar system. Notwithstanding this, it was felt that the DARC should expend efforts to seek exclusion of such systems from the amateur allocation in the band.

Juergen Dahms, DC0DA, then led off with a slide presentation on the use of transverters for the GHz-bands during the BBT, probably the most demanding portable contest. He therefore not only discussed the technical requirements, but also addressed operational issues under extreme weather conditions. As always, Juergen had made good on his promise and had submitted his papers shortly after the last convention (a late paper on his design of a new transmit mixer for 122 GHz will also be included in the proceedings).

Next up was Michael Kuhne, DB6NT, who, like no other, has made invaluable contributions to the advancement of amateur microwave technology through his many innovations and design ideas. He gave a lecture on Transverter-technology evolution through the years using the example of a 10 GHz transverter. Comparing different tranverter design concepts, he demonstrated the dramatic changes that have occurred over the past 30 years, starting with Gunnplexers and culminating in state-of-the-art tranverters featuring frequency disciplined oscillators and output power levels of up to 50 watts.

Harald Gerlach, DL2SAX, then shared his experience with the 'Perseus' SDR-receiver. This unit has already been identified as a potent measuring instrument by a number of other authors. Harald focused on the application of this receiver in contesting activities, notably VHF/UHF/SHF contests. A series of block diagrams highlighted a range of applications, including its use in combination with the HRD ('Ham Radio Deluxe') software to control a transverter.

Peter-Juergen, DJ7GP, then covered the home brewing of a rubidium frequency standard to discipline microwave oscillators, an area that has seen growing interest since the previous year's convention. He managed to convince the many doubters amongst the delegates that this homebrew standard was capable of competing with GPS-disciplined oscillators, both from a technical as well a financial standpoint.

As always, the lunch break offered a choice between nose bagging or having one's own CW/SSB transceivers' or homespun DDS/PLL oscillators' signals subjected to rigorous analysis by Wolfgang-Henning Rech's (DF9IC) "Perseus" SDR-receiver or on Dirk Fischer's (DK2FD) comprehensive radio test set, comprising a spectrum analyser and plotter. A surprisingly large number of test candidates were queuing up, despite this facility being available again for the first time in many years.

After the break Dirk Fischer, DK2FD, presented details on the design, manufacture and performance measurements of parabolic reflectors for frequencies ranging from 24 GHz through 241 GHz. The reflectors are spun from a solid blank to ensure dimensional accuracy and structural rigidity. Dirk demonstrated the manufacturing process with a series of photographs. Measured gain of the prototypes is in line with the intended performance. In a next optimization step it is intended to reduce weight to a maximum of 1 kg. The technique yields easy to manufacture rigid, high-gain reflectors for the higher frequency microwave bands. To finish off, Dirk gave a brief progress update on the further development of the DL0V-contest group's microwave activities at the Münster polytechnic institute as it relates to the practically oriented training offered.

Another newcomer speaker, Hans Ulrich Schmidt, DJ6TA, lectured on a topic, few of the delegates had ever heard of before - "Computer control of HPIB/GPIB test equipment and control program "MESSZEIT" (Measuring Time)". These interfaces enable a range of microwave test equipment, such as spectrum analysers, frequency generators and network analysers to communicate with one another. As such equipment is now becoming available on the surplus market at reasonable prices, their interconnection by computer, as opposed to operating the individual units autonomously, is worth considering. As few amateurs are aware of this facility, Hans Ulrich gave useful hints on how to achieve this and how to program the networked test equipment using the freely available control software 'Messzeit'.

Ewald Goebel, DK2DB, then spoke to the age-old topic of the 'accurate frequency'. Following a brief excursion into the history of frequency measurement up to present-day GPS receivers which are at the heart of every homebrew frequency standard. Having discussed the suitability and availability of various GPS modules, Ewald detailed the construction of a 10 MHz frequency standard which, in addition to providing a high-stability 10 Mhz reference signal, outputs other useful information, such as geographical coordinates, QTH locator, IARU beacon data and so on.

Lorenz Oelschlegel, DL6NCI, probably one of the best-known rainscatter-operators in Europe, in his paper defined portable equipment requirements to participate successfully in the contest and rain scatter scene. His two-part presentation provided hints on aids to facilitate optimum exploitation of the prevailing DX conditions, chief among them an Internet connection to access DX clusters and to track the all-important rain clouds live.

In the technical part of his paper, Lorenz identified present-day standard components of a portable set-up; a minimum transmitter output of 10 watts and frequency-disciplined oscillator reflect the technical progress that would have been unthinkable just a few years ago.

Wolf-Henning Rech, DF9IC, a regular speaker without whom the convention is impossible to imagine, presented two papers. He first discussed the use of multiplexers for the microwave bands, which he proposes to include in the ongoing concept development of a new multi-band station for 13cm through 6cm. The use of a multiplexer would obviate the need for multiple coax cables to enable concurrent multi-band reception. Henning explained the function of such a multiplexer, its hardware realisation (strip line PC board) and presented measured performance using spectrum analyser screen shots.

In the second part of his presentation Wolf-Henning introduced his concept for a universal frequency generation scheme for 950 through 1300 MHz This single signal source, complemented by different multipliers, is to be employed in the various stages of his aforementioned multi-band station. The multipliers are somewhat unusual in that, contrary to the standard approach employing two or three stages, Wolf-Henning's concept uses a symmetrical frequency doubler without output filters driving a single harmonic generator and selectively filtering the fourth, fifth and sixth harmonic from its output spectrum. The selected frequency then passes through helical filters for final filtering. The advantage of this concept lies in the ease of achieving extended frequency coverage by simple means. The only note worth adding is that this kind of multiplier is driven by the PLL controlled VCXO that Wolf-Henning introduced at the previous year's convention.

Being the final speaker at such events is always a somewhat thankless task as delegates' attention span is at that stage considerably shortened. Nevertheless, the announcement of a report on the construction of 76 GHz-transverter served to revive interest once more. Roland Becker, DK4RC, managed to fill the final half hour with a veritable fireworks of technical details and ideas to delineate the state of the art at 76 GHz. Owing to the (albeit limited) availability of amplifier chips (Chip AUH 318) it is possible to generate approx. 50 mW in SSB, respectively achieve a noise figure of 9.5 dB when using the chip as a receiver module. However, a drop of bitterness should not go unmentioned: sourcing the chip and, more importantly, the need for a bonding machine to mount the case less chip is beyond the capability of the average microwave amateur constructor. This notwithstanding, Roland's design proposal offers scope for bridging heretofore unimaginable distances at this power level.

In the wrap-up session, DJ6XV, thanked the presenters for their efforts on behalf of delegates and expressed his delight at the unexpectedly large number of papers submitted. He concluded that the repeated appeals in past years to ensure the continued success of the convention through the active support of authors and presenters clearly had borne fruit. However, it had also become clear that the presentation of some ten papers appeared to be the maximum that could be crammed into a one-day convention.

The panel discussion underlined the significant interest in the opportunity provided by Wolf-Henning and his "Perseus"-receiver and Dirk Fischer with his communication test set to enable delegates' equipment to be tested. It proved to be a welcome revival of this old practice from the early days of the convention.

DL4BBU thanked the papers' authors for their timely submission of manuscripts which greatly alleviated the usual stress of producing the proceedings. Delegates were asked to submit photos taken during the convention to allow those not able to participate to gain an impression of the goings on.

As usual, all papers will be compiled into the official proceedings which will be available from DJ6XV at cost (EUR 8.00 + EUR 3.00 P&P). Ordering information is available on the convention's web site which also lists all available proceedings and their contents of past conventions under 'Rückblick'.

Heinrich Frerichs,DC6CF, will, for the 32nd year running produce the 'official' convention video. Order should be place with: Heinrich Frerichs, DC6CF, Süderstraße 12, D-26835 Holtland

Remark: The corresponding pictures you'll find in the German version on the website under 'Rückblick/2009/Bilder'.

Peter, DL4BBU