PIC-Controlled Expedition CaveRadio

(Click on image to enlarge)
This is the latest design until now.
Go directly to downloads

As all our designs, it's mainly based on the Hey-phone radio with some little changes.
For costsaving reasons its frequency is set at 86,956 KHz (same as the french Nicola-radio) instead of 87KHz, but it works fine with both systems.

This radio can be used as a normal cave-radio (including radiolocation), for this you need two of these sets.
It is also designed to use with the earlier surface radio as well as the new surface radio (will be published end of November).

The earlier surface radio is only capable of making a connection to a VHF-radio.
This version is also capable to send commands for calling the VHF-radio at the basecamp (like an alarmsignal), record and playback messages.

All functions are generated and controlled by a PIC16F84 microcontroller.
For these the PIC generates 3 tones. SOT (Start Of Transmission) 1200Hz, COMMand (1500Hz and EOT (End Of Transmission) 1950Hz.

The use:
Normal use:
When the PTT-button is pressed; transmission begins and an SOT is generated which will be repeated every 10 seconds.
This repeated SOT-function will be detected by the surface radio (and sustain the VHF-link for another 21 sec).
When the PTT-button is released; EOT is generated and transmission will stop.

Calling the basecamp is possible by setting the Command-switch once (Call-led = on).
After pressing (and release) the PTT-button the following tones are generated: SOT - COMM (1x) - EOT.

Playback any recorded message (will be stored at the surface-radio) is possible by setting the Command-switch twice (Play-led = on)
After pressing (and release) the PTT-button the following tones are generated: SOT - COMM (2x) - EOT.

Recording any message (max 40 seconds) is possible by setting the Command-switch three times (REC-led will flash for 40 seconds).
After pressing (and please hold this time) the PTT-button the following tones are generated: SOT - COMM (3x).
After releasing PTT-button an EOT will be generated and transmission will stop.

This function can be used for radiolocation.
Set the switch to 'beacon on'. An SOT and EOT will be generated until the switch is off.
At every SOT/EOT-cycle there will be a 2 seconds pause where the radio is switched to receiving mode (so communication is still possible).

Adjusting the receiver:
It's very simple; Set your tonegenerator at about 89KHz with 20cm wire at the output.
Adjust the (TOKO)coils L5 & L6 until best result is heard.
VR3 is to set the AGC. VR3 has little influence but the AGC works fine.

Adjusting the transmitter:
Set your tonegenerator at 1500Hz & 20mV and connect its output to the mic-input.
Press the PTT-button and adjust (TOKO)coil L8 to maximal amplitude at your scope.
Adjust VR1 until maximal amplitude (at a nice sine wave).
Then connect the mic-input to Gnd and adjust RV2 until you get a flat line (as flat as possible)
Repeat this procedure until best results are made.
note: L7 needs no adjustment.

Construction details:
(Click on images to enlarge)

Mounted PCB
Inside radio
Battery compartment


Downloads for PIC-controlled Expedition CaveRadio

Electrical design.
You can download two files:
Cave radio (sept 2001).PDF (use Adobe Acrobat)
Radio design (sept 2001).DSN (made with Proteus lite)

You can download five files:
PCB Cave radio (bottomcopper).PDF (1:1 bottomcopper / PCB-film ready)
PCB Cave radio (topcopper).PDF (1:1 topcopper / PCB-film ready)
PCB Cave radio montage bottom.PDF (with all parts at the PCB-bottom)
PCB Cave radio montage top.PDF (with all parts at the PCB-top)
RadioPCB (sept 2001).LYT (made with Proteus lite)

Construction details.
Construction.cdr (CorelDraw-file of construction)
Front-layout 14-9-2001.PDF
Front-layout caveradio 14-9-2001.PUB (MS Publisher file)

Partlist cave-radio.xls
Partlist cave-radio.PDF

tonecoder.psf (Basic-like program, readable with a simple text-editor, like notepad)
tonecoder.asm (assembled sourcefile, also readable with a simple text-editor)
tonecoder.hex (to be programmed in the PIC16F84)