[Johnson] Tube Designation

[Peter Markavage]

Same issue as the Pacemaker or any balanced modulator that uses a pair of
twin triode tubes. As Carl pointed out in another e-mail, those tubes
should be matched as close as possible or you'll wind up being the cat
chasing its tail trying to get adequate and consistent carrier null.

Pete, wa2cwa
http://www.manualman.com

On Tue, 22 Apr 2008 15:55:09 -0400 "David C. Hallam"
<dhallam at rapidsys.com> writes:
> What about the Hallicrafters HT-37?  Since it uses an almost 
> identical
> system, is the carrier balance as difficult to achieve and maintain 
> with it?
> 
> David
> KC2JD/4
> 
> > -----Original Message-----
> > From: johnson-bounces at mailman.qth.net
> > [mailto:johnson-bounces at mailman.qth.net]On Behalf Of Langston, 
> Mike
> > Sent: Tuesday, April 22, 2008 3:04 PM
> > To: Peter Markavage
> > Cc: johnson at mailman.qth.net
> > Subject: RE: [Johnson] Tube Designation
> >
> >
> > Last time I tuned a Pacemaker was 1978. I was feeding a T-bolt 
> and
> > remember that I couldn't depend on the Pacemaker meter for 
> accurate
> > carrier null. I had an output meter downstream of the T-bolt and 
> nulled
> > for minimum reading on the output meter. I don't remember what 
> tubes
> > were in it.
> >
> > Mike KL7CD
> >
> > -----Original Message-----
> > From: johnson-bounces at mailman.qth.net
> > [mailto:johnson-bounces at mailman.qth.net] On Behalf Of Peter 
> Markavage
> > Sent: Tuesday, April 22, 2008 12:48 PM
> > To: Johnson at mailman.qth.net
> > Subject: Re: [Johnson] Tube Designation
> >
> > I seem to remember when I had the 12AT7's in the Heath SB-10, I 
> had to
> > constantly ride the carrier null pots with each transmission. 
> Replacing
> > the tubes with 6201's and replacing the null pots with 10 turn 
> devices
> > cured that problem along with the improved carrier suppression.
> >
> > Pete, wa2cwa
> > http://www.manualman.com
> >
> > On Tue, 22 Apr 2008 13:21:19 -0400 "David C. Hallam"
> > <dhallam at rapidsys.com> writes:
> > > Pete,
> > >
> > > I can't seem anything one way or the other.  Right now the 
> Pacemaker
> > > is a
> > > work in progress.  When I am finished refurbishing maybe I will 
> run
> > > some
> > > tests.  I can try a 12AT7, ECC-81, 6201, and any other MilSpec
> > > variants I
> > > can get my hands on and look the carrier and side band 
> suppression
> > > on my
> > > spectrum analyzer.
> > >
> > > David
> > > KC2JD/4
> > Johnson mailing list
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> >
> >
> >
> >
> 
> 
> 
>