ΜBITX

Notes on µBITX assembly and use.

Assembly

Parts that took some time to decide on approach to:

• Case: used a cookie tin as a case.
• Mic assembly: TODO

Antenna setup

Inverted V dipole made with Amateur Radio Supplies 20m dipole antenna wire (two 18' strands, trimmed, wrapped around insulators, strung up in attic) and 450Ω window line.

• Originally was sent two 16ft strands, which is really too short. Customer service was great and sent me the 18ft strands and a prepaid return envelope for the 16ft strands.

QRPGuys Multi Z Tuner

• See my notes on assembly for the Multi Z Tuner

QRPGuys 12W dummy load

• Items from QRPGuys took about 2 weeks from date of order to arrive.

Mods

Applied during assembly:

• Added a fuse before diode (succeeded, afaict)

Attempted after tested working:

• Mitigating heat on LM7805:
  • Added a small 5V switching power supply before LM7805 (failed; created too much noise)
  • Relocation of LM7805 to case (succeeded, but got leads switched the first time and smoked the nano)
• Dim LCD (failed—no effect)

Also working:

• Using CEC firmware

Plan to attempt at some point:

• TX LED
• SWR meter
• Red-on-black display (for night-time operation)
• Foot-pedal controlled TX
• Some sort of audio pre-processing?
• Leveling out power?
• Fix filters??