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Jason:
Ok for the QRP to barefoot operator, but what about someone that at least occasionally uses an amplifier? I've got a couple of swr/wattmeters (two meters) that provide everything I need, though they are a bit difficult to read at QRP levels. Autek WM-1 is one of them and currently available, and the other is a SignalCrafter 30 (may not be full name and model, but also not available any more). Both have ranges for 20w, 200w and 2000w full scale, and show average or peak readings. They tend to match one another pretty well, especially considering the WM-1 is less than a year old and the other is probably 20 years old.... Will your meter be able to perform as well? I've found that most LED based metering circuits are horribly inaccurate compared to a needle based meter.... On the other hand, I'd love to see a new meter available, particularly one that would work from qrp levels all the way up to legal limits.... while providing both SWR and Power metering. I really really dislike dual needle interpreted displays. Thanks --Rick AH7H Jason Hsu wrote: Last semester, I designed and built the QROP Meter for my graduate school independent study project. Thanks to those of you who helped me with certain thorny issues, such as transformers and DC amplification. Go to my web page at http://www.jasonhsu.com/ee.html to learn how to build the instrument. What makes my SWR/wattmeter different from the numerous versions available from MFJ and the numerous homebrew designs out there? 1. Works from 200mW to 100W! You get the best of both worlds! MFJ SWR/wattmeters don't work at QRP, and QRP SWR/wattmeters can't handle 100W. Tuning up at 1W instead of 100W reduces the QRM you cause by 20dB, or over 3 S units! You can also safely change the tuner's inductance taps WHILE transmitting at 1W. 2. GOOD resolution at SWR values above 3 and even above 5! This can be very handy at 160m and 80/75m. 3. 10-LED display for the SWR meter and another 10-LED display for the wattmeter: No more squinting at cross-needle meters! 4. More accuracy at low power levels: Most SWR meters understate SWR at low power levels due to the infamous diode drop loss. My design compensates for this and allows accurate SWR measurements at QRP power levels. Let me know what you think, and feel free to contact me if you have any questions or suggestions. If you decide to build the QROP Meter, let me know how it goes. Jason Hsu, AG4DG |
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