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Re: [Amps] Fwd: rx noise?

To: Ian White GM3SEK <gm3sek@ifwtech.co.uk>,<amps@contesting.com>
Subject: Re: [Amps] Fwd: rx noise?
From: <d.cutter@ntlworld.com>
Date: Tue, 9 Dec 2008 10:32:41 +0000
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Did the regulator have proper bypass in the first place or was this a problem 
just waiting to pop out?  Capacitor-to-regulator distance is critical.  I've 
never known a regulator go funny if it was properly set up in the first place.  
As Pease would say "do what the manufacturer tells you or all bets are off." 

David
G3UNA

> 
> From: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
> Date: 2008/12/09 Tue AM 08:39:07 GMT
> To: amps@contesting.com
> Subject: Re: [Amps] Fwd:  rx noise?
> 
> David Robbins K1TTT wrote:
> >I think the noise in that one is solved... take a look at the scope pic 
> >for a 12v regulator with a 2v p-p oscillation on it at: 
> >http://wiki.k1ttt.net/2008%20Maintenance%20and%20Upgrade%20Blog.ashx?NoR
> >edir ect=1#Bottom That's one repaired, another one tested clean for 
> >now, and 5 more to go.
> >
> Glad you found the problem, Dave. By coincidence(?) someone recently 
> found a similar problem with a 78xx in a GaAsFET preamp that had been OK 
> for years, but then decided to become unstable.
> 
> Any thoughts about what changed to trigger the instability? (Aside from 
> it being CQWW weekend, and the regulator having poor stability margins.)
> 
> 
> -- 
> 
> 73 from Ian GM3SEK
> http://www.ifwtech.co.uk/g3sek
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> 

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