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Jason, The circuit looks very useful. The layout of the LEDs is not very typical, which makes it a bit unnatural to use. That is easy to change. Can you provide some inside photographs to show how you did the circuit layout? I am not sure why people even use SWR as a measurement for reflected power. Perhaps it provides a nice mathematic simplification, but it is a very quirky and unnatural scale for human operators: 1) it does not go to zero, 2) it is hard to read/write/and even say, 3) without a forward reading, a SWR of 1:1 could simply indicate no forward power, and the useful range ends at 3. What is needed is a scale that based on a 2-dimentional vector. For example, magnitude and angle of a vector that is formed from an X-axis of forward power and a y-axis of reflected power. The difficulty is mostly converting this to a graphical representation. An array of 100 LEDs is not very practical (10 x 10), but perhaps a tiny LCD is. A small LCD and microprocessor could be cheaper and easier to read than cross needles. Andy WA3LTJ 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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