The Transmitter
Nautel ND2000
During the summer of 2025 Arctic 252 was given an old airport beacon transmitter, a Nautel ND2000 serial number 123 made in 1989. It's a 500W transmitter. It had sat in a cabin for many years after it was switched off. It was originally transmitting the callsign AKU on 432 kHz in the town of Ivalo for Ivalo airport. It was one of 4 location beacons around Ivalo that were setup in 1990 and ran for many years until decommissioned.
These beacon signals were heard up to 1000km away.
The Nautel ND2000 has built in redundancy with two sides A and B that are able to be used independently. If the PA, Exciter or PSU fail then it will switch over automatically to continue broadcasting. The transmitter can also run from a 48V battery backup.
The transmitter came with it's matching NX2000TUB ATU plus beacon wideband antenna and original manuals plus tech notes/logs on old repairs. It's great that this 36 year old transmitter is being saved and put into use.
Getting on 252 kHz LW
Moving day.....
With help from a friend we took out the PA units and other transmitter sections so that the main cabinet could be put into a car! It was quite a task but it fitted very well and was safely transported home. The transmitter was covered in fly dirts and it was unknown at that point if it was still working as everything had been disconnected for many years. It was given a thorough clean and and setup temporarily in a cabin.
Setting up and testing
The beacon transmitter was originally setup only for a keyed 400hz tone on 432 kHz so it first had to be setup for 252 kHz. As the transmitter covers 190kHz to 535kHz this part was relatively simple. A few coil taps were changed and other connectors. It was found that this old transmitter did not have a PLL board installed but instead an older style crystal oscillator board. New 4032 kHz HC49 crystals were ordered and were soldered directly into the board with the change in multiplier to 16 in order to get 252 kHz.
After setting up the ATU and wiring everything up it was ready to switch on for the first time in years. It did not disappoint, everything worked as it should, a great testament to the build quality of Nautel. The transmitter runs at 600W carrier with no issues and with further setup and mods it is capable of a bit more.
For testing an inverted-L antenna was used, it gave good audio bandwidth but it's reach was very limited to around 250 km using a good reception antenna. Reports came in from Sweden with good audio and reports from further South in Finland of a carrier detect at 750km were very promising.
The audio bandwidth
The audio from this beacon transmitter was very narrow so the modulation board was modified. The capacitors were changed for the low-pass and high-pass filters to allow a fuller audio bandwidth. During testing a failure of a multiplexer IC lead to the modifying of the modulator board again. This time the multiplexer section was disconnected via the removal of a resistor. The modulator board can now only be used for AM broadcast. The keyer board was also removed from both the exciters.
Next steps.....
Antenna and studio
The original beacon wideband antenna will be modified and tested for 252 kHz. The capacitance hat is only 10m at present and the main mast section needs to be taller.
An inverted-L antenna from a taller mast will be tested also.
The studio setup is taking place but things have been slow in regards to equipment. The station has been offered an Optimod 9200 audio processor so that will arrive hopefully at some point.
Initial testing showed that the transmitter was working well and audio was good. Further setting up of the audio will take place to get the best out of this old Nautel. It will never be up to a great standard but with LW it will be be good enough. Longwave transmitters have been extremely hard to buy with very little leads even to used ones, stations tend to keep or scrap the old transmitters.
The transmitter will be moved from it's temporary location before the winter to it's permanent home and a studio of sorts will be setup.
It's a slow and steady process and there is very likely a delay in the stations start. Everything tends to take a lot longer than expected. Help is short on the ground and time is limited.
To the wonderful people who have helped Arctic get this far it is very much appreciated.
With thanks also to Traficom, Gramex and Teosto for their help in licensing something of an oddity that this LW station is in today's modern world.