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How to add an RF protection device to amplifier?




 
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Author Topic: How to add an RF protection device to amplifier?  (Read 11349 times)
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KA2QFX
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Mark


« Reply #25 on: March 17, 2011, 08:06:54 PM »

Tom,
You still have a problem. Steve's board is a wonderful circuit but as I recall is tracks the current vs. voltage from the modulator stage. If either one falls out of the comparator window the circuit "trips".  I suppose you could compare final PA current to a non-varying reference voltage if you reduced the sensitivity of the comparator. A question Steve could easily resolve.


But you still need a way of detecting the reflected power and something for either condition to act upon to shut-r-down.  Speaking of "r". Did you name this contraption yet? 

Mark 
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K1JJ
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"Let's go kayaking, Tommy!" - Yaz


« Reply #26 on: March 17, 2011, 08:31:11 PM »

Mark,

Good point about the current vs: voltage tracking.   Yes, maybe if the Voltage is set to a certain threshold value, the current will hit the desired preset point and trigger the comparator. I think that wud work, but Steve wud know for sure.  I need a trigger at above 10A at 30V.

The LP Filter has a reflected SWR output, so I'm all set there.

I plan to use the overload hi or lo to trigger a SS device to shut down the amplifier bias or PTT circuit voltage.  No relays involved.

T
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed. 

Nothing like a new homebrew rig. Come into the shack, flip on the switches and everything works perfectly.

And, nothing like an old dog.
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