Monday, December 27, 2010

Beacon keyer IK0WRB

If you ever build the beacon, or if you have the idea of building one, there is a part that every beacon needs, the keyer. Various beacon keyer designs are available on the internet but IK0WRB solution was the one that I prefer to use. Up to now I built a several keyers and all of them a working perfectly. As a matter of fact, the 144 MHz 9A0BVS beacon is running more that 3 years with this keyer where small reed relay !! is switching the power for the buffer stage. At the beginning nobody believed that the relay will last so long. It is still working.

As a spare solution, there is a keyer based on the transistor switch, where no mechanical parts are included. The schematic is standard IK0WRB keyer with a small modification where two transistors are used in a switch configuration. The first NPN transistor is used to key the input to the ground, and the second PNP transistor is used to switch the positive voltage. The jumper is used to chose beteween this two options, depending on the type of the beacon you are planing to use.

One of the things that make this project unique is the possibility to change the text and the format of the message on a very convenient way, just by tweaking the options in the windows based application written  by the author. The same application is generating at the end the HEX file to be programmed in the PIC 16F84. Of course, the message speed and the duration of the beacon carrier can be selected. Another nice feature is the possibility to use any convenient crystal frequency for this project. As I have a bunch of standard 3.579 MHz crystals, this is my favorite.

All the project can be done using the SMD technology where complete PCB can be really small. Between using the tiny SMD components and drilling the holes on the PCB for the standard components I prefer to use the SMD :-) . As this can be a beginner's project I made a PCB using the standard components with the socket for the micro-controller where the same can be easily reprogrammed with the new messages for a different beacons.

The keyer from the photo is a part of the 23cm beacon where positive voltage is keyed for the 648>1296 frequency doubler. The shape of the signal is looking good without any clicks or chirp. Simple keyer for all beacon builders....

No comments:

Post a Comment