My Mini-Mod 2021 completes a set of three Pantry Transmitters for use around the house. It also encouraged me to box-up the one I built from David's PCB a few years ago. The third unit is one I've had a few years now, it's the AM-03 that used to be sold by Geoff Hopkins. It worked well, but is no longer made.
- I'll need to re-visit the values of the audio input resistors - I used the 'Tape Out' of my Stereo Tuner to run the AM-03, but this is too much for the Mini-Mod.
- The awkward spacing of the Phono sockets on the newer units was in an attempt to mount a 30cm telescopic aerial (donated from a 'Home Bargains' set-top TV aerial). I thought it would make for a neat solution, but the short antenna really limits the range.
- A trip to 'Wilkinsons' for some new Speaker wire gives me a nice 2m antenna length and early experiments gave an improved reception when connecting the battery -ve to a nearby radiator. So I've added a Crocodile clip to this earth lead.
- I was concerned about the proximity of the PP3 battery to the oscillator coil, but if the battery moves anywhere, it'll be out of the case and the whole thing stops working!
- There looks enough space to mount a Bluetooth Module inside - but I'm sure that will release a whole load of misery with noise. I do have some of those handy DC-DC Isolators now, but I think that's one for later.
- Due to a 'picking error', CPC sent me a 470pF cap instead of 100pF for C2. Currently using an 82pF Tantalum cap that was purchased for my Magnetic Loop project.
Whilst dismantling the AM-03 to get measurements for the panels, I seem to have killed it. The battery positive lead had come detached and may have contacted something on the PCB. The moral of that story is to use decent connecting wire. I had used some nice looking red/black cable salvaged from an old 'foreign' made car accessory. The conductors inside are extremely thin and break off far too easily.
Thanks again to Peter for sharing-out these PCBs. Anyone else finished theirs yet?
SR