EMRFD Message Archive 4785

Message Date From Subject
4785 2010-06-25 19:00:34 dixonglennb 20M 10W BS170 transmitter proto
This is the latest version of the transmitter section of a QRP xcvr I'm designing. The design goal is to make the transmitter easy enough for a beginner to build, so it will eventually have a PCB.

I've posted a schematic pdf in the files section under 20M 10W BS170 XMT and a photo of the ugly proto in the AC7ZN photo album. The proto contains extra stuff such as RF current transformers so may be confusing, but hopefully the schematic is clear enough. The schematic logic supply says 5V but I'm actually using 5.6V.

You can use ceramics in place of the polystyrene capacitors, but you may get poorer efficiency. I used Fairchild BS170's and would be interested to know if other brands work as well. The topology is a switched current scheme, which some people also classify as either class E or class F. The measured efficiency of the transmitter was over 95%.

If any of you decide to build a proto I would be very interested in your experiences.

Thanks and 73,
Back to field day,

Glenn AC7ZN