ON0TB
Repeater at Signal Botrange

Locator - JO30bm MAP
 50° 30'7.51"N / 6° 5'34.22"O  718m ASL

ON0TB = (Top of BeNeLux) = Höchster Punkt in der BeNeLux

For this moment NO CTCSS or Tone, near future  only trough CTCSS 131,8 Hz
FOR ESTIMATED COVERAGES SEE Photo Gallery

Technical Info

The repeater is based on a commercial base station from the 1990 era mobile Phone system owned by Belgacom.  It is a Nordic made Ericsson / Radiosystem AB RS9044 radio, that is built in a single rack unit, containing highly shielded compartments.

The receiver uses a single power GaAsfet, a very high level 23 dBm passive mixer and a dual conversion IF strip with 12,5 kHz Crystal filtering and Automatic frequency control.

Both synthesisers use direct frequency VCO’s based on a semi rigid cable resonator.

The driver delivers 5 Watts to a 4 transistor dual parallel power stage, capable of 70 Watts output.

The repeater has extensive on board diagnostics, and measuring equipment.

It contains limiter and compander circuitry, that is not used, apart from a hard limiter on the output limiting peak deviation up to a maximum of 3 kHz.  Below that value the audio response is flat from 50 Hz till 3400 Hz.  This allows also D-star digital data to pass through this system, although not recommended due to the unpleasant sounds..

The original controller firmware was reverse engineered by Dennis Koller, PA4DEN, and he made an alternative firmware allowing this radio top work on 430-440 MHz.  It needs to be modified extensively however, as the helical filter circuits were designed for 460-470 MHz, so high level plumber skills are needed.

High attention was given to the reduction of PIM (passive intermodulation reduction).  For instance no foil coax cable was used in the duplex filter assembly, only pure silver braided cable.  Same with the antenna cable run: only solid copper 10 meter long Hi-Flex cable by Eupen was used, as well as Andrews low PIM connectors.

The duplexer is a six cavity Bandpass/bandreject filter.  It uses quarter wave resonators to notch out the unwanted transmitter noise on the RX frequency, and the TX frequency overload on the RX input.  The coupling loops are also tuned in order to get an asymmetrical graph, to obtain very low insertion loss <0,7 dB and extreme high rejection losses >100 dB.

The combined noise/signal strength squelch system is known to have issues with temperature drift, so soon a CTCSS decoder including high pass digital audio filters will be installed, based on an FX365 CML chipset.  This will also deal with current adjacent channel QRM, where too large signals on 439,000 or 439,025 trigger the open squelch system.

There is no forced cooling as the radio is designed to stay cool due to the extensive cooling ribs all along the radio body.

Target output power is 50 watts after the duplex filter, also the legal limit for repeaters in Belgium.

 

 

Status January 2015Pedro M.J. Wyns ON7WP