There it is, my second BITX transceiver, this one for 20 and 40. Once I got the VFO sorted out, this one went together very quickly. Obviously experienced gained on the first project was a big help.
I followed Farhan's advice and characterized the 11 MHz crystals in the filter. Then I used the AADE filter design software to build a 3 KHz filter. Using my Arduino DDS signal generator and the new Rigol 'scope, I was able to do a manual sweep across the passband -- it looked very close to what was predicted by the software.
This morning I built the bandpass filter for 20. As soon as that was done, I fired up the receiver. This was an amazing experience for me: a homebrew receiver that worked right away! That never happened before. I'm listening to 20 meters now. It sounds great. I even managed to demodulate and display some SSTV. The VFO seems very stable.
I still have to build the RF amplifier stages, the bandpass filter for 40 and low pass filters for 20 and 40 (I know Steve Smith is watching!). Then it will be time for cabinetry. I guess I should put some paint or varnish on that walnut box. Any recommendations? I'll line it (on the inside) with copper flashing material.
In response to popular demand, "SolderSmoke -- Global Adventures in Wireless Electronics" is now available as an e-book for Amazon's Kindle.
Here's the site:
For the print version:
For shipping from a printer in the U.S. (probably better for N. American buyers) Click here: SolderSmoke USA Version
For shipping from a printer in the UK, Spain, or the USA (probably better for UK and other European buyers)
Click here: SolderSmoke EU Version
The two versions are identical, except for a minor difference in the paper used. That's why the prices are a bit different.
Bill's OTHER Book (Warning: Not About Radio)
Click on the image to learn more
W4HBK's QRSS Grabber: The Amazing Pensacola Snapper (Live!)