A Visit to HB9AMH

After my visit to JO50, I got an invite to visit Arnold HB9AMH. I am sure that to most UK microwave operators the callsign HB9AMH/P and HB9MIN/P are very well known. HB9MIN is no longer active, but Arnold is, and a trip to his portable location was on the bill during the two days I was there. Unlike my trip to JO50, the journey to Arnold was about 130kms and took just over an hour in the car, The sun was very bright and the journey went without a hitch.

As I neared Arnold's village I was aware of some very impressive mountains to my right (the north), these were the Jura Mountains and are just as effective as the Alps at attenuating signals. To my left I would have been able to see the Alps if the weather had been clear.

Arnold home QTH is on first sights, not very impressive. He is to the south of the Jura on the south side of a large hill, he is just above most of the village and has a clear takeoff to the south. To most people you would think that this was a very unpromising place for microwave activity, but you would be wrong. More of that later.

HB9AMH Home Shack

Arnolds shack at home is rather impressive, he has a dedicated shack with most of the amplifiers and transverters in the roof space. In his shack he had some good test equipment, digital rotator controllers with 0.1 degree resolution. A nice feature of his rotator controller is a locator map of Europe on the wall with a Perspex pointer which sweeps around the map in synchronisation with his rotator. His driver radio for 6cms and 3cms is a Kenwood TR751E. The shack also included his new project a 45W TWT amplifier for 3cms, the finishing touches being made to the home made power supply.

HB9AMH Home 3cms Transverter and TWT HB9AMH Home 6cms TWT

A trip into the roof space revealed an Aladdin's Cave of equipment, apart from his 6cms and 3cms transverters (DB6NT naturally) and his TWT amplifiers, he has many older unused amplifiers from days past. These included some rather beefy 23cms equipment and 70cms amplifiers. His rotator was particularly interesting. The mast was an 80mm pipe, and the rotator was at the base of the mast with another mast fixing just below the roof itself. The rotator motor appeared rather small but was geared down heavily and it had no problems moving the antennas and surviving storms.

HB9AMH Home Antennas HB9AMH Home Antennas

Back down in the shack were many QSL cards from his days on 23cms EME when he used about 500W and a homemade 3m mesh dish. The dish was located in the same location that is now used for his microwave antennas which consist of a 1.2m dish for 6cms and 3cms, and assorted yagis for 2m, 70cms and 23cms. The 3cms feed is connected to the transverter with waveguide, while the 6cms system uses co-ax and suffers increased losses because of this.


In the afternoon we went to the portable QTH. Since the location is so high, the weather there is much more severe, and while in the valley we were in the sun and the snow had melted a few weeks before, this was not the case up on his mountain. In the summer it is possible to drive right to the portable shack, but this time we had to leave the car about two kilometres away down the mountain. We changed our shoes into proper heavy walking boots and we wrapped up as if we were going to the Arctic. For safety we also put sun block on our faces and Arnold wore sun glasses.

The walk was difficult and slow. The snow was about one metre deep for most of the walk and this caused problems if your foot broke the layer of ice on the surface. Altogether the walk up took about three hours. The location is amazing, it is located in a hay loft of a (summer) farm and has a clear takeoff from west to east via north, an almost exact complement to his home location. This was also the location of the HB9HB 2m beacon until recently, but this has now been moved to a nearby mountain because the interference to his IF's was getting to be too much.

HB9AMH/P Antennas HB9AMH/P Antennas

The first job was to remove the storm guys that prevent the mast loaded with three dishes from bending or breaking. There were two yagis on the mast for 2m and 70cms which were much worse for wear than the dishes and in dire need of replacement once the weather gets better. Arnold has two masts at the portable QTH, the main mast includes all bands including 6cms and 3cms, there is a separate dish which is also for 6cms and 3cms which is below the others but is larger.

HB9AMH/P Selection of Awards

The shack itself is separated from the rest of the hay loft by walls and has a separate bedroom. Almost every wall has certificates for winning just about every Swiss contest in the 1970s and 1980s, the oldest I found was a plate from 1969. In one corner of the loft itself was a complete K2RIW amplifier and power supply, all of the big amplifiers were located outside of the shack in order to keep the noise level down from the fans.

HB9AMH/P Shack

The shack itself is well kitted out with what appeared to be a separate radio for each band, many of them being IC-202s. The amplifiers for the microwave bands are in the shack and waveguide goes up to the antennas to reduce losses and for allowing easy maintenance. At the portable location Arnold also has 24 GHz with about 0.5W in addition to 6cms and 3cms. A quick check of the beacons showed almost no conditions or activity. A surprise came on 6cms when he showed me the signal from DB0KHT (JO40FE) on 6cms at a distance of 346kms, a steady S2, the 3cms equivalent was not audible. After about an hour listening to white noise we put the guys back on and walked back to the car. By the time we reached the car it was dark and we had the joy of driving down narrow lanes in a forest with a large drop on one side of the road, but Arnold was up to the challenge, after all he has been going there for 35 years !

The path between HB9AMH and HB9OK The next day Arnold showed me what he could do from his home location. An immediate surprise was that HB9OK (JN45MW) is always audible on 3cms. Although the distance is only 185kms, there is a lot of rock in the way in the shape of the Alps. The signal appears on the direct bearing and not via an obvious reflection point. The associated 6cms beacon at HB9OK was not audible but that was put down to the increased losses on that band because of the co-ax. The 2m beacon at HB9OK is only slightly stronger than the 3cms beacon. 

One of the saving graces of the Alps for microwaves is their ability to be good reflectors, this was also demonstrated by using Mt. Blanc which is line of sight. By beaming towards it he is able to hear not only local beacons but also a couple of French ones, one of which, F6FGI, is a personal beacon which is beamed at Mt. Blanc on purpose. We tried phoning F6FGI who is in fact German (as is Arnold himself) but he wasn't around for a test. Arnold is going to experiment with circular polarisation for 3cms as he has done tests that seem to indicate that much of the fading on reflected signals is caused by polarisation changes

Another reflection test was done using a nearby electricity pylon which produced good signals from nearby beacons, signals were only 10dB down on the direct signals in some cases. An interesting device that Arnold has built is a wideband receiver which is used for measuring noise, it's part of the PANFI project from DUBUS some years ago. With this it was possible to see Sun noise as well as noise from nearby houses, the ground and the cold sky. With this receiver it is also possible to detect some of the mountains which Arnold can use for reflections.

As if that wasn't enough, he was also experimenting with locking an oscillator to the time base of ZDF using a module from ID Electronics in Germany. In many ways this is similar to the modules designed by CT1DMK and described in DUBUS recently. Personally I think that locking to GPS is probably a better was of moving forward and is somewhat more portable also. At this stage I introduced Arnold to both the G8ACE OCXO and 24GHz amplifiers and I think it's possibly that he will investigate them further.

After lunch at a local Italian restaurant and a rest, I traveled back to Zürich and hit the rush hour around the city which made the return journey less enjoyable than the journey going.

I would like to thank Arnold for showing me around and proving that the true spirit of amateur radio experimentation is still alive. He gave me many ideas that I hope one day to follow up on. I sincerely hope that I am able to work him once I have returned to the UK.


Last updated on 28.03.2003