To:  amps@contesting.com 

Subject:  Re: [Amps] Looking for Alpha 87A expertise 
From:  Jim <jimw7ry@gmail.com> 
Date:  Sun, 14 Mar 2021 21:16:15 0500 
Listpost:  <mailto:amps@contesting.com> 
Doug...How fast is a PIN diode? How fast is a 1N4007 in an Alpha 87? If you have not measured their speed, how can you make that statement? Thanks 73 Jim W7RY On 3/14/2021 7:59 PM, Douglas L via Amps wrote: I have doubts about replacing those PIN diodes with 1N4007’s. The 1N4007’s don’t switch quickly enough to substitute for a PIN. 73, Doug/WA1TUTOn Mar 14, 2021, at 3:16 PM, Steve Thompson <g8gsq72@gmail.com> wrote: 2. Is a drop from 900V opencircuit to 730V typical when disconnecting/reconnecting the "R" bias lead at the HV board? I'm wondering if I have another leaky PIN diode or cap to ground that is loading it down. It doesn't take much to load the bias supply given that it inherently has 880k of series resistance.I don't know the 87A circuits, but assuming the 900V/880k supply is loaded with a reverse biassed diode with 3.9M across it, the current in the 3.9M will drop the voltage to a calculated 734V  close enough to what you're seeing so I'd guess it's ok. I'd hazard a guess that the 3.9M resistor(s) are there to try and avoid problems from static build up. Sorry, can't help with anything else. Steve G8GSQ _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps_______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps 
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