N9FH automatic antenna controller project: 

This one has been dragging on for quite some time. Several years ago I got the idea to use a Basic Stamp as the brains for an intelligent antenna controller for SO2R contesting.  In my case the primary motivation is being too cheap to buy commercial stuff as well as that there is nothing on the market that can do what by box will when it's done.   In a nutshell, the controller takes BCD band input from two radios (Yaesu band data standard) and allows the selection of any unique combination of 32 outputs per radio.  Each output sources 12VDC at 350mA to control antenna selection relays.   The real strength of this device is that it allows a "software patch panel" mapping bands onto selected outputs to control combinations of relays.  Each band has a "default" antenna as well as three other "good" choices that can be stepped though with user input.  The software mapping approach allows for a number of interesting capabilities that would be hard to do in hardware.  Multiband antennas, multiple choices per band, and rapid reconfiguration for different contests (e.g., DX vs domestic) or after hardware changes are all easy to handle. 

Phase I:  8x2 relay box. 

The first step was to build the box that would handle switching two radios to multiple antennas. Seems simple enough but to make something that would be reliable, "transparent" at HF, and handle a KW I had to first learn how to make double sided PC boards.  Got some board layout software and tried a 4x1 switch as a warmup using the surplus relays I had stashed for the final project.  Here's one of the four 4x1 switches I made.  They work great so far and have come in quite handy.  Turned out to be a lot cheaper than buying commercial switches. 

The next step was to extend the design to the 8x2 switch.  I ran two copies of the board since I had a very large pile of 20A relays (paid $0.50 ea for them!).  Here is a picture of the first completed box on the left.  You can see the Sonalert mounted on the lid - it's there to let you know when you try to put both radios on the same antenna.  The relays are wired to "lock out" an antenna port once it's selected so you can't really mess up but the alarm tells you that you've got an open port on the "last" radio.  Insertion loss and port to port isolation seem pretty darn good - at least as far as I've been able to quantify them.  The "final" version is currently in use in the shack.  You can see it in position on the right below. 

Phase II: Software

So now that we have something to control it's time to build the controller.  The Stamp makes that pretty easy.  I've got 32 bits of TTL level I/O ready to go along with a built in BASIC interpreter, memory, voltage regulator, etc.  For I/O I'm using a 40x4 backlit LCD that will sit at operator eye level.  Four momentary pushbuttons on the front of the box (and a second parallel set on a "remote control" next to the keyer paddle) provide user input for manual selection and mode changes.  Antenna / band data is formatted in a spreadsheet on the PC and downloaded into the Stamp. Full time RS232 connection also allows for a variety of forms of "host" interaction with the PC.  So far, in addition to fully automatic operation there is a "manual" mode that allows you to step though all of the possible antennas sequentially using the up and down buttons on the box. 

Here's what it looked like as of June 2003.  I had the software finished around Christmas and have started on the hardware. 

Phase III: Controller hardware

The controller is built on two 4x6 boards.  I'm using vectorboard rather than making "real" PC boards for it.  That may be a mistake since construction is such a pain that I've been avoiding it.  One board holds the Stamp, some big voltage regulators, optoisolators for the inputs, drivers for the Dunestar bandpass filters, and misc I/O.  The second board has two sets of 4->16 decoders for each radio as well as a bunch of Darlington transistor arrays to drive the relays.  I hope to have it running for the January 2004 NAQP.   At the rate I've been going I doubt it.....

Got any ideas related to this project?  If so, send me an email.