Saturday 19 February 2011

New Controller Board

Having confirmed operation of the divider scheme on the output of the multi-mode beacon's Si570 local oscillator, I set about making a new controller board.

The new board shared most of the features (and PCB layout) of the old version, adding only the divide chain (using the old TTL chip) and control for the BandPass filter. To date, I had set the BandPass board up by manually setting the band select lines and pulling down the "chip enable" to latch the address (corresponding to the desired band) into the (74LS137) de-multiplexer. Now, I could arrange for the PIC16F873 to do all the hard work for me!

Here's the new board...

You can see the Si570 "piggy-back" surface mount board and the new divider network (with a jumper to select divide by 2 or 4). I also up-rated the power supply arrangements by substituting a 7805 for the 78L05 that was on the original controller. The two four-way headers at the bottom of the image provide ground, two select lines and an enable for the BandPass and a switchable output LowPass (when I finally get round to building it).

Here's the new board in situ...

A few more lines of code were written and now there's a satisfying "clunk" from the relays every time I change band.

Operation confirmed by my first spot after the mods - this time from Erich, dk6ug...

Now I shall be able to flip back and forth between bands with laughable ease (as the great H E L Falkus used to say).

...-.- de m0xpd

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