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. . . PROGRAMMABLE AUTOMATIC QRP RADIO BEACON FOR 3,5 MHz
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This is an interesting and simple project for making an automatic programmable QRP radio beacon for 3.5 MHz (80 meters band).
The automatc keyer is made around the PIC16F84A PIC-controller chip and can be programmed with text that will be automatically transmitted via the RF transmitter, in the form of morse signs in the air through the antenna.
The signal from the PIC Controller goes to the base of the transistor T1 (BC547 or similar), so in that rhythm the transistor switch on and off the RF transmitter. Transmitter is made of the integrated circuit CD4001 (which acting as an oscillator) and the output RF amplifier with the transistor T2 (BD139 -16). Output RF power is 1 to 3 W.
click on the schematic diagran above to view it in better resolution
The schematic below shows only the PIC16F84A PIC controller on the mounting plate at a time when I experimented with it, and this link shows how the controller works:
click on the picture above to view it in better resolution
The finished working prototype with mounted elements on a printed board can be seen on this video.
The printed circuit board (PCB) has been made previous for an ARDF transmitter (ARDF foxhunt transmitter) which schematic diagram is similar to this for the radio beacon, so some of the elements are not mounted on the board.
On this video you can see and hear the signal from this QRP Radio-Beacon located in my home in Macedonia, as it is received (1100 km away) in Czech Republic via a web-based SDR receiver in Czech Republic.
On this video you can see and hear the signal from this QRP Radio-Beacon located in my home in Macedonia, as it is received (2200 km away) in Sweden via a web-based SDR receiver in Sweden.
On this video you can see and hear the signal from this QRP Radio-Beacon located in my home in Macedonia, as it is received (1780 km away) in Holland via a web-based SDR receiver in Netherlands.
I left my Radio-Beacon working automatically during several evenings from January 28 to February 2, 2018. The antenna was a simple dipole mounted as an inverted "V" so that the highest center point was erected about 9 meters from the ground, and the antenna ends were about 2.5 meters from the ground. The coaxial cable was 30 meters long RG-6 (75 ohms impedance). Below are the reports, from which, one can conclude that the signal was received all over Europe, although the transmited RF-power output was only 1 W:
click on the picture above to view it in better resolution
click on the picture above to view it in better resolution
click on the picture above to view it in better resolution
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Mile Kokotov (2018)
MIle Kokotov, M.Sc. is industrial engineer manager and has a master`s degree in technical science with almost 40 years expirience in RF-technics. He is Acttual President of The Radio Amateur Society of Macedonia
Feel free to visit other articles and projects on his website
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