Introduction

Since the the WG3I PIC keyer was published in Feedpoint(1) and the Eastern Coast VHF Proceedings (2) there have been requests to adapt the design for automatically calling CQ in contests.. The cycle requested has generally been as follows:-

 Key transmitter

Short delay to allow relays to settle (~100mS)

Send message

Unkey transmitter

Wait to see if anyone responds

Start again

The advantages of using a PIC keyer to call CQ is that it doesnt tie up an expensive "fully functioned keyer" on each band to do the job, also it always has the correct message; no more trying to work out how to program a keyer with frozen fingers that you have never seen before (this may explain why one hears "CQ NST" being sent so often in contests?)

Investigation of the code of the original PIC keyer has revealed that the CQ mode of opeartion can be accomodated with few program changes in the same PIC16C54 chip with the addition of a few extra interface components..

For details of the philosophy behind the original design and how it works see my original article (1) (2). I will only discuss the modifications here.

The circuit is shown in Figure 1. There are two independant cw keyed outputs from pin 6 and pin 13 of the PIC and two independant PTT outputs, pins 7 and 8 . Pin 6 and 7 are used to drive transistors which may be used to drive external relays a requirement especially if the transmitter's PTT line is high voltage or high current. Pins 7 and 8 are used to drive LEDs through current limiting resistors to indicate the state of the keyer.

It should be noted that altering the cw sending speed with VR1 alters the PICS clock speed which also controls the length of the "wait". The "wait"was designed to provide a 25s delay at 12wpm but will alter proportionally with cw speed, the delay is around 20s at 15wpm.

Hardware

A small PCB, designated WG3I015 has been designed for the project is shown in Figure 2.. The component overlay is shown in  Figure 3 . The component list is shown in Table 1 . The microprocessor code as a zipped .asm file is available cwcq.zip. Both a programmed PIC and complete kits including a programmed PIC chip are available from the Author.

Conclusions

This article was written to update a previous design to hopefully allow contestants to easily activate as many bands as possible during UHF/SHF contests. It is hoped that this will facilitate the discovery of many previously unworked microwave paths

References

1.Feedpoint, Newsletter of North Texas Microwave Society, Dec 95/Jan 96 issue

2.Proceedings of the 21st Eastern VHF/UHF Conference, Aug 95 p74-76

 
  Figure 1: Circuit diagram

Figure2: PCB Layout

Figure 3: Board Overlay

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