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DRB 32-4

4 Channel Coherent HF Receiver

Application at the Arcala Extremes Project

arcala dx

Possibly the highest 14 MHz antenna in the world:

4x 6-elements yagis (105m tower)


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 conditions.

Outstanding Features

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):


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 world.

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 Montero):

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 & snowflakes

antenna measurements

Preparing measurements

coherent receiver drb-32

Taking measurements