OH3TR

Tampereen teekkarien radiokerho
BOX 692
FIN-33101 Tampere, Finland
QRV 145,375 MHz
& 434,950 (-2,0) MHz
Tel. +358 40 952 6701

OH3RTR Repeaters in Hervanta, Tampere, Finland

Currently OH3TR operates two FM speech repeaters and an amateur television repeater under the callsign OH3RTR. Our 70 cm speech repeater, ATV repeater and 6 m speech repeater receiver are co-located with the OH3SHF microwave beacons at the Hervanta water tower where we also have our VHF/UHF/microwave contest station.

Downtown Tampere by Night

This picture is taken from the water tower observation platform to the northwest where you can see downtown Tampere with the landmark Näsinneula observation tower, with its OH3RNE repeaters. It should give you an idea of our site. You can find more pictures and a video clip on the page of our VHF/UHF/SHF contest station.

The 6 m repeater transmitter is located at our clubhouse, also in Hervanta.


OH3RTR repeater and OH3SHF beacon cabinets

On the right you can see our equipment racks at the water tower site.

In the rack on the right, top to bottom: 70 cm FM repeater, 70 cm DMR repeater, the GPS-based time and frequency reference for the beacons, 5.7/10 GHz beacon exciter, 70 cm RX multicoupler, 70 cm FM repeater computer interface, 6m repeater RX and 70 cm link TX to the transmitter site, 6 m and ATV power supplies, ATV PA, ATV up- and down converter, and the two units at the bottom are the ATV IF stages.

The rack on the left holds the 24 GHz beacon exiter, some computer and APRS equipment and the 70 cm TX multicoupler with the duplexer on top of it.


OH3RTR 6 m speech repeater

QRT for the moment, TX antenna gone bad, RL ~ 5 dB :( (9.2016 onwards)

  • Channel RF95 (51.950 MHz out / 51.350 MHz in)
  • Receiver at the Hervanta water tower, KP11VK
  • RX antenna Aerial side mounted vertical dipole at 220 m asl / 65 m agl
  • Transmitter at the club station at Tampere University of Technology, KP11WK
  • TX power 50 watts
  • TX antenna Aerial side mounted vertical dipole at 184 m asl / 32 m agl
  • RX-TX link low power NBFM link at 433.975 MHz
  • Radio equipment modified from Nokia BSR80 and BSR420 (Kyodo KG110) trunked PMR base stations
  • Controller RYYDLAB(tm) 8032 card by OH1NPK
  • Firmware by OH3NYB
  • Full DTMF remote control of operating parameters as well as DTMF user functions.
  • Duplex filters are not needed due to the fact that the TX and RX sites are situated about 1.3 kms apart. There are also tall apartment buildings in the first Fresnel zone between the sites that help to provide more than 110 dB isolation between the receiver and transmitter antennas. However, we use a home made heavy duty low pass filter by OH1FF with more than 70 dB attenuation at 100 MHz to protect the local BC listeners.
  • The repeater provides mobile coverage inside a 50 to 80 km radius, depending on the direction. Stations as far as from the U.K. have been contacted with some help from the sporadic E layer propagation mode.

OH3RTR 70 cm speech repeater QRT, waiting for service

The repeater is again linked with the RATS R.NET linked repeater network

  • Channel RU396 (former RU14, 434.950 MHz out / 432.950 MHz in), access with 123.0 Hz CTCSS
  • Location Hervanta water tower, KP11VK
  • RX antenna Kathrein 5 dBd omnidirectional at 225 m asl/ 70 m agl
  • Transmitter about 30 W ERP
  • TX antenna Kathrein 5 dBd omnidirectional at 212 m asl / 57 m agl
  • Radio equipment modified from a Nokia BSR450 (Kyodo KG110) trunked PMR base station
  • K6VHF RX preamplifier and a Celwave bandpass filter
  • PC-based controller running locally made software. Interfaces radio equipment with a CM108-based USB sound card.
  • Duplex filters modified of two Nokia 410 MHz one-channel FM link duplexers, 4 cavities each, with more than 100 dB notch and about 2 dB passband loss
  • The receiver system seems to be very sensitive now with the new RX antenna and preamplifier. Low power stations with less than 1 W handhelds inside a moving vehicle have had excellent signals to the repeater from more than 30 kms away. The mobile coverage radius with a 35 watt radio is more than 50 kilometres with the downlink signal quality as the limiting factor.

OH3RNE 70 cm DMR repeater

We also house the OH3RNE DMR repeater (434.525 MHz out / 432.525 MHz in).

The 70 cm repeaters share antennas through a multicoupler system so the coverage is pretty much the same.


OH3RTR 23 cm FM ATV repeater RIP

  • Frequency 1252.000 MHz out / 1282.000 MHz in
  • Location Hervanta water tower, KP11VK

More info about the ATV repeater in memoriam and Team OH3TR ATV operations.


Future developments

Many future developments have been discussed. A gateway between the 6 m and 70 cm repeaters has been about to be built for a long time, as the essential parts are already there. The Kyodo base stations have a balanced remote audio line and there are also unused control pins in the RYYDLAB controller, so the hardest work is going to be in keeping our overworked software guru awake long enough to get the necessary modifications made.

There have also been plans to increase the portable coverage of the 70 cm repeater even more by a diversity reception system. The system would basically consist of several receivers with directional antennas to the most important directions (e.g. downtown, main highways and the university/campus area) and a signal/noise voter that will choose the best available signal. With 11 dBd panel antennas we could improve the received signal from the main directions with 6 dB compared to the omnidirectional antenna we have now. Some of our members have showed interest in improving the LDG 68HC11 based 8-channel voter published in an April 1996 QST article and writing their own firmware to it, and we already have some surplus 450 MHz NMT base station receivers and antennas so who knows what will happen...

We have also discussed about linking the speech repeaters with the OH3RNE 23 cm speech repeater (output at 1297.000 MHz) using a 86 MHz NBFM receiver connected in the ATV repeater RX IF line and a 70 cm receiver at the OH3RNE site tuned to the OH3RTR 70 cm output. Or maybe we'll build a 23 cm speech repeater of our own with a Nokia TMN-1 NMT900 phone, who knows...

Team OH3TR is also involved in technical support to the other repeaters (fi) in Tampere area.

Please have a look at our repeater links. Although the explanations are in Finnish, most pages we link to are in English.

Please point your link to .shtml-files instead of .html-files, when linking to OH3TR pages. Thank you!

Team OH3TR - Simply the Best

© OH3TR 1996-2017 (disclaimer)
Last updated: Wednesday, 05-Apr-2017 18:17:42 EEST