Amateur Beacon Projects

Introduction

Beacons, frequency reference stations and telemetry systems are a very interesting aspect of Amateur Radio. The biggest advantage of a beacon is that it is always there when you need it! Quite a few aspects of beacon design and use are different from normal Amateur Radio operation, and deserve to be considered separately. On these pages we look at various aspects of building, using and maintaining these useful devices.

With the sunspot peak past and radio propagation slowly falling off on the higher bands over the next few years, there will be heightened interest by Amateur Radio operators in the lower bands. Amateurs need to know what propation exists at various radio frequencies at different times of the day. Unfortunately there are few beacons on the lower bands. The lower bands require special consideration, and special beacon techniques. Special propagation study beacons and slow QSO transmitters are also of interest, especially on LF.

The higher bands are quiet, and signals are there, or they are not, as conditions dictate. The lower bands are much more noisy, and signals are present for much of the time, but are often buried in noise or signals from other parts of the world. The propagation mechanisms are much more complex, requiring a different beacon strategy for these frequencies.

This web site describes a low power beacon system to be used for propagation and performance tests on the lower bands, and sophisticated LF and precision frequency transmitters.

There are several different applications that come into the general category of beacon stations:

• General propagation beacons (aimed at indicating when there is a band opening)
• Specialized propagation beacons (for ionospheric study)
• Precision frequency transmissions
• Telemetry devices
• Very slow QSO transmitters and beacons (generally on LF)

The different applications are differentiated by the type of modulation used, power level, frequency accuracy and type of data transmitted. Most of the propagation beacons use simple Morse ID and carrier, while some (for example the IARU & NCDXF beacons on the higher HF bands), use a sophisticated sequence of Morse ID and multi-level carrier in a coordinated time sequence.

The author is of the opinion that other ID modes would be more useful, and advocates two modes as being especially useful - Hellschreiber, and DominoEX. To prove the point, the author offers multi-mode beacon keyers with Hellschreiber modes, and is developing a (potentially GPS locked) DominoEX beacon keyer. These modes are rather easier to generate than some of the other suggested modes, and do not require a linear transmitter.

Several things about a beacon station differ from normal Amateur stations:

• Transmitters have to operate for extended periods, and need to be specially designed.
• Generally low power is used, and often the power level needs to be switched.
• Often several keying modes are used, requiring a sophisticated keying device.
• In some applications extreme carrier accuracy and stability are required.
• Unusual modulation techniques can be used.
• There is generally no associated receiver. Or at least, the receiver is somewhere else entirely!
• The equipment is frequently installed at a remote site, and must be highly reliable.

While special transmitters can be built, and are certainly easy enough for low power (see the Precision Frequency Exciter for HF and its Power Amplifier as an example), it is also quite easy to recycle old commercial SSB transceivers to do the job. The Codan 6801 is the author's favourite - reliable, stable, suitable for most applications, and capable of 10W output forever and 100W peak. It is also easily modified to Amateur frequencies and can be easily converted to frequency control with a DDS (Direct Digital Synthesizer).

These various aspects of beacon design are treated on separate pages. Select them from the menu above.

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