Sunday, July 22, 2012

Radio Habana's 74HC240 QRPp TX Circuit


Whilst perusing the QRZ Forums yesterday, I ran across a post about a 74HC240-based TX. I followed the link to the schematic and it didn't look familiar. Not familiar because I knew I'd stashed away a similar schematic for the same kind of TX in my files and it didn't look like that one on QRZ.com. Unusually, my search for my schematic was brief. In fact, I didn't have to look far at all, it was in a nearby hanging paper holder almost within arm's reach.

I was going to add the link to my schematic as a reply to the QRZ posting, but I soon found out that the URL on the schematic was no good, and a Google search of Arnie Coro, CO2KK, didn't find his circuit, either. So, I decided to revive this particular circuit on the web once again. Thank goodness for the hard copy!

The instructions and circuit (which I fully intend to implement one day ..., heh heh) are on two pages, which I've scanned, zip'd, and linked on the Kits and Homebrew page, reached in this blog's menu above. The final scans are larger, more detailed than the image here, so you should be able to read it easily. Certainly, it looks like a fun and fairly easy circuit to put together. 

The instructions say you can build it for 10, 15 or 20 meters (QRPp 10M beacon, anyone?). The coil winding form recommended is a Bic pen! It takes 8 VDC input and supposedly puts out about 500 mW.

If anyone gets this put together, I'm sure you'll let us know, right? 

Do you have any small radio circuits like this that you've built or would want to share?  73!

1 comment:

Thanks very much for your comment! 73, Casey

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