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Author Topic: Is 36 volt zener necessary on you DIY QRP output stage?  (Read 4502 times)
W1VT
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Posts: 2485




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« Reply #15 on: October 16, 2017, 08:20:14 AM »

If you have 12 volt devices you want to use, you could also drop the voltage to 5 or 6 volts.  A lower voltage may be more practical for some.

Zack W1VT
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AE7TE
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Posts: 53




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« Reply #16 on: October 18, 2017, 12:42:26 AM »

In the QRP transmitters I've used, I usually hard-wire in a 500 ohm resistor made of two 1K, 1w resistors in parallel. During normal operation, 4 watts into 50 ohms is 14.14v RMS. This same voltage into 500 ohms is 400 mW. So, you lose only a little bit of power in the final load. What this resistor network does is hard-limit the SWR to 10:1 and absorb any super-high voltage spikes that might be caused by inductive elements. It won't completely prevent any sort of damage...it's kind of a damage control method. At QRP levels, the resistors used to implement this can be common 1/2w resistors and still withstand anything the QRP transmitter will throw out.

Ed AE7TE
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