TRG operates all possible modes and technologies; FM, P25, D-STAR, DMR, POCSAG, packet radio , ATV etc. Internationally they are known for the 10m repeater DF0MOT which utilizes split site technology on two separate towers on Feldberg, RX on Kleiner Feldberg and TX on Großer Feldberg.
I have operated through TRG repeaters many times during my trips to Germany, and recently during a work trip to Germany I had extra time to visit Feldberg to see how the site actually looks like. I talked with Ralf DF2RK over their DMR repeater and he was able to give me a small tour also of the repeater site up in the hill. I was quite happy for that, it's always very nice to see installations like that to get ideas for our own systems!
|Großer Feldberg communications towers, amateur radio antennas on the right side tower. 10m repeater TX antenna is located in the small tower in the lowest part of the building.|
All repeaters are located up in the tower quite near the steel mast on top of the tower. Repeaters use sector antennas which provide good gain and possibility for direction-based voting if wanted (not done there)
Repeater cabinet is filled with very familiar radios, Motorola UHF Quantar for both analog FM and P25 on 70cm. The APCO25 repeater has an second scanning receiver to create links to other P25 repeaters in the region. Using a scanning second receiver is quite ingenious method of linking P25 repeaters, which by other means would be very expensive as they were not really meant or priced for amateur community!
The D-STAR stack features an 70cm Digital Voice repeater and 23cm Digital Voice + Digital Data units. The repeaters belong to the US-Trust and run IRCddb so all the latest bells and whistles are in users disposal :)
On top of the stack there is a Motorola DR3000 70cm DMR repeater which is hooked to the worldwide DMR-MARC network.
The "indoor" antennas possible in the Feldberg-style towers are something special which we in Finland are unable to utilize as all communication towers are open-air sites and all antenna assemblies must be planned and build to be rugged and weatherproof. There are several antennas concealed in the wooden tower which is not only easy for maintenance but also enable also to use homebrew antennas as the antennas do not need to meet all possible commercial specs. There were several 23cm packet radio link antennas inside the building, and link antennas for the P25 repeater scanning receiver antennas towards the other P25 repeaters.
TRG operates also many packet radio links which operate on 23cm band. There were several link stretches looking at remote packet radio nodes.
The day we visited the site was very windy and foggy, so it was not possible to visit the top of the tower but only have a quick look through the hatch how the things look like. I was quite sure the hatch would fly away, it was *that* windy :)
The red panel antennas just above the hatch are used by amateur radio, one "level" for RX and other for combined TX. Vertical antennas shown in the right picture are for D-STAR 23cm.
There was quite significant amount of Wimax and 5GHz Wi-Fi antennas also. No wonder that some local ISP providing wireless has spotted this site to be an optimal place for long-haul trunks :)
The installallations on Großer Feldberg are very professionally done and represent amateur radio engineering very well. Thanks Ralf for showing me around!