2009-02-18
Keying the world.
Home callsign and service callsign, e.g. OZ7IGY and OZ7IGY/A.
Home locator and service locator, e.g. JO55WM and JO65ER.
Extra message that can be used to indicate propagation, e.g. "AUR".
Easy change of callsigns, locators and extra message in the software.
Instead of sending a key down "message" it is possible to send "Last letter ID."
Variable duty cycle, 100% or 50%, to save power.
Keying all outputs synchronously or asynchronously, i.e. one at a time in order to minimise the load difference on the power supply.
Enabling a RX period for monitoring the beacon frequency.
DIP switch controlled message and functions.
Software and microcontroller offer room for many more features.
| DIP | Function | On | Off |
| 1 | Call | Service call | Normal call |
| 2 | Send locator | No | Yes |
| 3 | Locator | Service locator | Normal locator |
| 4 | Duty cycle | 50% | 100% |
| 5 | Last letter ID* | Send LLID | Send carrier |
| 6 | Extra message | Send extra message | No extra message |
| 7 | RX pause | Yes | No |
| 8 | Keying | Sequenced | All keyed output |
*: overrides duty cycle.
The easiest way to connect the beacon keyer to a RS-232 interface is by using a straight serial cable, i.e. pin 1 to pin 1 etc.
Download the necessary PCB files here, courtesy Mathias, DH4FAJ, and Bent, OZ1HTB.
| Component | Value |
| R1, R2 | 4,7 kΩ |
| R3, R4, R5 | 10 kΩ |
| R6 | 100 Ω |
| R7, R8, R9, R10, R11 | 560 Ω |
| C1, C2 | 22 pF |
| C3, C4 | 1 µF, 25 V |
| C5, C6, C7, C8, C9, C10, C11 | 1 nF |
| D1, D2, D3, D4, D5, D6, D7 | 1N4148 |
| D8 | 1N4001 |
| D9, D10, D11, D12, D13 | LED 5 mm |
| I1 | 7805 |
| I2 | PIC16F84 |
| Q1, Q2, Q3, Q4, Q5 | BC337 |
| S1 | 9 pin D-sub female |
| S2 | 8 positions DIP switch |
| S3 | 3 pin header |
| S4 | 2 pin jumper |
| S5 | 23 pin header |
| X1 (most low cost crystals will work) | Crystal, max 4 MHz |
| Z1 | 18 pin DIL socket |
5B4CY CN8MC CU8DUB DB0AD DB0MMO DJ5UP DL1GBF IW4EHZ IZ4PSG/B K8EB/B LX0FOUR OE5QL OX4MB OY6BEC OZ4UHF OZ7IGY PS8RF SK6QW/B SV2DCD/B SV2JL/B SV5VHF
If you would like me to make the beacon keying software for you it is necessary that you specify the parameters shown in the table below. Otherwise get the microPascal compiler.
| Parameter | Description | Max | Example |
| X-tal freq. | The frequency of the crystal used in the beacon keyer. [MHz] | 4 | 3,2758 |
| Call | The callsign that is sent when operating from the normal location. [Chars] | 8 | OZ7IGY |
| Service call | The callsign that is sent when the beacon is in service mode. [Chars] | 8 | OZ7IGY/A |
| Locator | The locator that is sent when operating from the normal location. [Chars] | 8 | JO55WM |
| Service locator | Locator sent when the beacon is in service mode and operating form an alternative location. [Chars] | 8 | JO65ER |
| Extra message | An extra message sent when activated, e.g. about propagation. [Chars] | 3 | AUR |
| Number of IDs | The number of times the last letter (service) call ID is sent. | 254 | 10 |
| Key down | The duration that the beacon is sending a constant carrier, or 50% duty cycle. [Seconds] | 50 | 30 |
| Keying speed | The speed at which the beacon sends its message. [Letters Per Minute] | 200 | 60 |
| RX period | The duration of the pause when the PTT is deactivated. [Seconds] | 254 | 10 |
| Boot delay | Optional 10 s boot pause delay to prevent immediate PTT when powered up. [Yes/No] | - | N |
The purpose of this section is to describe what it takes to put a beacon on the air both the legal issues and the equipment.
Before you can put a beacon on the air several steps have to be performed.
Issues concerning the licensing is entirely up to you and your licensing authority. Before you begin you might want to read the IARU Region 1 VHF Committee guide lines.
Selecting a location if often the most difficult task. When evaluating a location the following parameters should be considered:
Choosing an operating frequency is more than finding a vacant frequency in your neighbourhood. The frequency, that you at first glance think is free, might be occupied elsewhere and the sole purpose of operating a beacon is to make it possible for others to monitor it. Therefore the frequency must be clear in the entire area the beacon is to cover at least 99% of the time.
The best, and perhaps only, way to get an operating frequency is to contact the frequency allocation manager for beacons, either nationally or at IARU regional level.
Table 1. Frequency tolerance and spacing. Source: IARU Region 1 VHF Committee.
| Band | 50 MHz | 70 MHz | 144 MHz | 432 MHz | 1,3 GHz |
| Frequency tolerance [ppm] | 4 | 2,8 | 1,4 | 1,0 | 0,8 |
| Frequency tolerance [Hz] | 200 | 200 | 200 | 400 | 1000 |
| Spacing between beacons [kHz] | 1 | 1 | 1 | 1 | 2-3 |
The next step is to get the necessary hardware which consists of:
The power supply, feeder cable, connectors and antenna(s) are assumed to be know stuff already. There are a number of ways to make the beacon hardware:
The cheapest way, and perhaps also best, is to get hold of an old land mobile base station. It offers the robustness required for a continuously operated beacon. A typical amateur radio station is not made for 24 hours of operation day after day.
Even if the radio is only made for FM it can be a perfect beacon. In fact most beacons are former land mobile FM radios. However, do not consider to audio modulate a FM beacon with a e.g. 1 kHz tone. This will generate a lot of side bands taking up a lot of bandwidth and will also reduce the power on the actual (carrier) operating frequency.
In order to save power, keeping the temperature down and the stress of the power amplifier the duty cycle of the keydown period may be reduced to e.g. 50%, sending a series of "E." However, experience shows that the output transistor(s) do not last longer. In fact they are prone to reduced life time due to thermal and current stress in the wire bondings. In order to prolong the life time of the equipment keep the temperature constant and below 40°C.
In order to key the beacon from the beacon keyer the modulation principle, CW or FSK, must be decided upon as it affects the keying circuit in the radio. Below are two schematic examples of CW and FSK keying.
Figure 1. CW keying of the beacon.
When keying the beacon in CW mode the carrier must be switched on and off. The best way to do this is as early in the TX chain as possible as this makes the switching of the actual transistor easier. On the other hand switching the oscillator on/off may result in a situation where the oscillation will not start and the frequency will become very instable. Keying the subsequent buffer stage will most likely result in chirp as the load impedance of the buffer stage changes whereby the oscillator is loaded differently during on/off. Therefore a later buffer stage with more isolation towards the oscillator is the best place, e.g. the second buffer stage.
Figure 2. FSK keying of the beacon.
When keying the beacon in FSK mode the carrier frequency is subject to a slight change made by switching in/out an additional capacitance in connection with the crystal.
Table 2. Frequency shift. Source: IARU Region 1 VHF Committee.
| Band | 50 MHz | 70 MHz | 144 MHz | 432 MHz | 1,3 GHz |
| F1A frequency shift [Hz] | 250 | 250 | 400 | 400 | 400 |
| Frequency at "space" [Hz] | nominal - 250 | nominal - 250 | nominal - 400 | nominal - 400 | nominal - 400 |
How the actual beacon keying is made depends entirely on the available radio.
Below are a number links to relevant beacon hardware sites:
Bo, OZ2M, www.rudius.net/oz2m