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Re: AIDC 3733's on 12 volts

How much "headroom" (volts needed for proper 12V regulation) does the 7812 
require?  Meaning, what is the "true minimum working" voltage that might be 
supplied to the 3733 without modification to voltage regulator?



At 11:39 AM 1/31/2002 -0500, you wrote:

> >From K5GNA:
>I have modified some of my AIDC 3733's to run on the 12 volts right out of 
>my IC 910H -- no power inserter needed.
>The internal regulator is a 7812, which is a 3 terminal 12 volt regulator 
>which powers the unit, but there is a separate internal 5 volt regulator 
>in the oscillator circuit.  With this second regulator, the oscillator 
>voltage (and frequency) are stable under any input voltages above 7 volts 
>or so.
>I cut the input and output leads loose on the 7812 and jumpered across the 
>circuit to run it directly off the 12 volts straight out of the 910H.  It 
>works well, but since I don't leave it on all the time, it drifts a few 
>minutes when first turned on.  With the 7812 regulator in the original 
>circuit, it generates some heat and provides some thermal stability when 
>left on continuously.  Without the 7812 regulator, the unit is quite 
>stable during a satellite pass.

Mark L. Hammond  [N8MH]

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