[Amps] Fwd: rx noise?

[David Robbins K1TTT]

According to the schematic there is a .1uf on the input, I didn't try to
follow the tracks to see where it was though.  There is no output side cap
at all.


David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
 

> -----Original Message-----
> From: d.cutter at ntlworld.com [mailto:d.cutter at ntlworld.com]
> Sent: Tuesday, December 09, 2008 10:33
> To: Ian White GM3SEK; amps at contesting.com
> Subject: Re: [Amps] Fwd: rx noise?
> 
> 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 at ifwtech.co.uk>
> > Date: 2008/12/09 Tue AM 08:39:07 GMT
> > To: amps at 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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