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Re: [Amps] Looking for Alpha 87A expertise

To: Benjamin Deovlet <w6fdu@aol.com>, amps@contesting.com
Subject: Re: [Amps] Looking for Alpha 87A expertise
From: Jim <jimw7ry@gmail.com>
Date: Sun, 14 Mar 2021 21:38:03 -0500
List-post: <mailto:amps@contesting.com>
How much slower?


Thanks
73
Jim W7RY

On 3/14/2021 9:31 PM, Benjamin Deovlet wrote:
From my design experience, the 1N400X diode is much much slower than PIN diodes.
Ben, W6FDU
In a message dated 3/14/2021 7:16:26 PM Pacific Standard Time, jimw7ry@gmail.com writes:

    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/WA1TUT
    >
    >
    >> On Mar 14, 2021, at 3:16 PM, Steve Thompson <g8gsq72@gmail.com
    <mailto:g8gsq72@gmail.com>> wrote:
    >>
    >>
    >>> 2.  Is a drop from 900V open-circuit 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
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