Revision 3
Revision 3 was the first board where everything worked in some fashion.
It had issues – and I wound up making some more changes – mostly due to level shifters!
he picture above shows a comparison of version 2 versus version 3. You can see that version 3 is quite a bit smaller (and consequently cheaper to fab as far as the PCB vendor is concerned).
I removed the PsoC from the top of the board – and decided to use a PsoC development board instead. Why – because I could solder pins onto it and plug it into the board. I also shifted (pun intended) to using ULN2003 Relay drivers for level shifters. I’ve know about these parts for 20 years -and they just work! They are also bullet proof and available in DIP packages. Note that is a theme here – DIP packaging where possible – avoid Surface Mount!
This is also the first time that I mounted the relays for the T/R switching.
What went wrong with this prototype? Well – first and foremost – I got the PsoC size off by about 0.05 inches – I couldn’t reliably plug it in. So to get things working with the filter FINALLY – I added 4 wires you see on the top of the card over to the inputs of the level shifters.
I finally had a transceiver!
Okay – why Rev4? Well – first off – get rid of the wires! Another little addition happened in the middle of this work – Pavel got a CODEC working – so I needed a place to plug a CODEC into the board. This would give me sound to/from the board without going through other options (USB sound wasn’t to terribly good at this point.)
Note – I had also found out about PiHPSDR at this point in time which was JUST what I needed as a GUI to make this a stand-a-lone radio!
I took this far enough that I was starting to work on how to mount it into a chasis.
The picture below shows the system sans 20W amplifier hooked up. This is the Rev3 board, the EB104 receive and transmit filters on the right mounted vertically on a PCB based stand. Note the ribbon cable connecting to the filters. One thing I noticed at this point was the receive performance had deteriorated.. more on that in the next section.
Finally, the picture below with a fully functional 20W transceiver and control, i.e. the Raspberry Pi based PiHPSDR system. The brick to the upper left is a TAPR 20W amplifier ( http://www.tapr.org/kits_pw.html ) Pennywhistle. This is the embodiment of the original Block Diagram. The only thing missing is the PSoC in the middle – didn’t need it.
Next: Revision 4