Radio Arkala is an extraordinary amateur radio
station (OH8X) in Northern Finland near the arctic circle. There are some special
challenges due to the severe weather in the form of very heavy icing and high wind
Antenna tower heights: 1x 105 m, 3x 60 m &
1x 40 m
Antenna gains: up to +21 dBi
Area: 20 ha / 45 acres
Here is some more background information kindly
provided by OH8OS (January 2008):
DEVELOPMENT OF INTELLIGENT ANTENNAS FOR THE ARKALA
During 2007 we have assembled a team of amateurs/professionals who will continue
the technical work as part of the Arcala Extremes project. The work is directed
towards adding intelligence (real-time control and adaptive operation) to the antennas
at Arkala. The goal is to improve the performance of the station for DX operation
and, particularly, for operation in the major global contests.
During this winter, we are concentrating on the big 14 MHz antenna, which consists
of 4 yagis 32 m, 55 m, 78 m and 101 m above ground. It can be regarded as a vertical
linear array of 4 antennas with 23 meters spacing.
In July we started the helicopter measurements
and the recording of real-world signals with the antenna. We have used a 4 channel
coherent HF receiver specially built by Rudolf Ille Communications Technology (Dipl.Ing.
Rudolf Ille) for this purpose.
During the helicopter measurements we have recorded the signals (voltages) from
all the 4 stacked antennas with the 4 channel receiver and a 4 channel data acquisition
system. We have concentrated on the direction of 240 degrees (Spain/Portugal/South
America). At the same time, we have recorded DRM and AM signals from Europe on
the adjacent 13 MHz broadcast band. In December we carried out a series of recordings
with an amateur station in Nevada (K6GNX). We recorded carrier, two tone and SSB
signals twice an hour during a 4 hour period.
The measurements have provided us the data
needed for creating a mathematical model for the antenna.
The antenna model and the recorded real-world signals have made possible to start
Matlab simulations of the algorithms needed for SNR maximization.
During 2008 we are looking forward to a long-term cooperation (assistance/contribution)
with a small number of enthusiastic and knowledgeable amateurs/professionals around
The work at Arkala goes back to the work
done in the Oulu area on rotating towers and stacked antennas since the early 1970s.
The work was started by OH8OS who invented the rotating tower in the late 1960s.
The work was continued during the 1970s by designing and building a number of rotating
stacked antennas for the 14 MHz band. During 1976-1986 the work was done in cooperation
between W6KPC and OH8OS. The largest 4 stack 2 bay 48 element antenna was taken
down in 1986.
Starting in summer 2007 (Pictures © by Luis Miguel García
Calibration of the 4 channel configuration
at Helsinki Polytechnic Stadia lab
Preparing helicopter measurements
Some pictures taken during winter 2007/2008:
M1 tower with 4x 14MHz stacked yagis, helicopter