I made a couple of additional
changes on my PCB layouts of your BBG fm transmitter circuit, schematic. This was the smallest
I could reasonably get the board size. As you can see, it now fits into
a Sucrets box with a 9V battery. Now that it all works properly (
flipping the varactor diode the right way around helped ) and I have a
PCB that fits the parts I have on hand, I can now move on and make -
generate a bunch of boards at once.
Because most other professional
transmitters (LEA, DTC, SpectraTek, etc.) use an antenna connector, I
opted to buy a bunch of SMA connectors and make a tuned antenna. I also
added a microphone jack that you can swap different mics in case one
I appreciate all the advice and encourage you gave me. This has been a fun project.
Update - Pete Jenner Has Built another BBG, this time in an "ALTOIDS" Tin Box.
Below are the photos he emailed me and - also some Tips for building the BBG in this type of Enclosure.
Some tips for your builders. Working with
Altoids tins as an enclosure is a great field-expedient. They are
readily available, easy to work with, and the same size as
expensivetransmitters. However, measure the center of the holes
carefully. The holes should be equally spaced from the bottom of the
lid to the bottom of the tin. Drill the holes undersize. The tin
tears easily, even with the sharpest drill bits. Use a hand-reamer to
get the proper fit and keep the holes round.
Cutting a square hole for the SPST switch is a
little more difficult - but again, mark and measure, then drill some
undersize holes side-by-side. Use a small file to shape the opening to
the right size,and test fit your switch often. Again, make sure the
hole/opening are underneath the lid but don't interfere with the PCB
board. Trial fit allcomponents.
Use the smallest jacks and connectors
possible. The mic jack is a Switchcraft TR2. Insulate the
bottom of the tin. I use overlapping strips of electrical tape. A very
thin piece of plastic could also be glued down. Then I hot glue the
board to the bottom of the tin--onto the tape. A builder could use
plastic stand-offs or washers, but they're not necessary.There is not a
lot of extra room in these tins. Everything will be snug, but
they will fit.