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Re: AMSAT-BB-digest V2001 #118



In a message dated 2/20/01 12:41:18 AM GMT Standard Time, 
owner-AMSAT-BB-digest@AMSAT.Org writes:

<< The G3PHO Drake 2880 Modification
 page shows the LNA circuit using
 2V for Vd on the MGA86576.
 
 The MGA86576 specs I have read show
 a Vd of 5V (and even 7V at high temp).
 
 Does anybody know why Vd was set at 2V?
 
 Thanks,
 Bill Washburn, WA6QGR 
 - >>

Hi  Bill.

As the originator of the data held at the G3PHO site I can say that it's 10V 
not 2V.
The Zener is then used as a Voltage dropper not a voltage stabiliser. This 
gives 10V - 2.7V =  7.3V    The is then a small loss over the 33R resistor 
which put the MGA86576 supply Voltsge very close to the 7V you mention.

Feel free to ask questions directly if you wish.    -    g0mrf@aol.com

good luck with the conversion.

73

David  G0MRF
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