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80m 3watt TX : ATX80

CLASSIC 80M TRANSMITTER FOR RADIO ORIENTEERING

ATX80

The 80m TX described here is the well known ON7YD ATX-80 and timer combined on one PCB and fitted in a standard folded aluminium enclosure.( regrettably no longer manufactured !)

For a full description of this popular design visit the ON7YD web site

Hardware Changes (from original ON7D)

  • Tactile button added, wired in parallel with the sync socket.
    Used for manual changing of the callsign
  • ‘TUNE’ header added. Uses RA4 port. For tuning-up an ATU using software switching. The original design required closing the ‘TX switch’ before the ‘KEY switch’, with the potential of cooking the output transistor if actioned incorrectly. (see original ON7YD docs).
Enclosure

The PIC timer and RF circuits have been combined in a PCB, to fit a standard AB28 folded aluminium box. The AB28 box is ideal because it neatly accommodates a 10xAA battery pack with the main PCB above. In operation, the unit is placed in a plastic bag and hidden in undergrowth. A plastic storage box, or plastic pipe could equally be utilized.

ATX80

note below: from the photo above

  • the fixing holes enlarged to slots, to allow the top to hinge.
  • the nearside bottom flange is folded flat, to allow the battery pack to be removed
  • the PCB is hung from the top flanges with 20mm M3 spacers.

ATX80
above: Using a slightly wider aluminium box, type AB23, allows the inclusion of a simple toroid T matching device.

PIC SOFTWARE You can use the original software by ON7YD or alternatively the G3ZOI software, which has been enhanced :-

  • for later PIC versions 16F628 and 16F628A
  • end-of-transmission callsign programmed into eeprom.
  • ability to change callsign.
  • software controlled tune-up switch.
  • transmits a short, fast burst of the ID (MOx), in the one hour before event start. To confirm the TX status to an event organizer.
Downloads

https://drive.google.com/drive/folders/1gMho2UD4E2a54gRHjz4MqLcvd6m0zDrO?usp=drive_link

  • Gerber File version 3 rev3 30-5-2026
  • PIC software