[AMRadio] Modulator design needed


Gary Schafer garyschafer at comcast.net
Sun Mar 26 14:24:26 EST 2006


Just remember if you are going to use a tube phase inverter rather than a
driver transformer the modulator tubes need to be run in AB1 and not AB2.
You can't run any grid current without a driver transformer. 
This leaves out 807's as modulators as you can't get very much power out of
them in AB1 but they are fine in AB2 as they are used in most rigs. Dx100
etc.

73
Gary  K4FMX


> -----Original Message-----
> From: amradio-bounces at mailman.qth.net [mailto:amradio-
> bounces at mailman.qth.net] On Behalf Of Peter Markavage
> Sent: Sunday, March 26, 2006 1:34 PM
> To: amradio at mailman.qth.net
> Subject: Re: [AMRadio] Modulator design needed
> 
> 12BY7 drives the driver transformer which, in turn drives the EL-34's.
> 
> Build a phase inverter, like many of the Hi-Fi amps that don't use a
> driver transformer to drive the EL-34's.
> 
> Pete, wa2cwa
> 
> On Sun, 26 Mar 2006 13:19:06 -0500 "Mike Sawyer" <w3slk at uplink.net>
> writes:
> > Bob,
> >     I suggest you look at the schematics again. The output of the
> > 5763 goes
> > no where near the modulator.  I don't have the schematics in front
> > of me but
> > I have done some extensive work in the audio section.
> > Mod-U-Lator,
> > Mike(y)
> > W3SLK
> > ----- Original Message -----
> > From: <rbethman at comcast.net>
> > To: <w1eof at hamnutz.com>; "Discussion of AM Radio"
> > <amradio at mailman.qth.net>;
> > "Discussion of AM Radio" <amradio at mailman.qth.net>
> > Sent: Sunday, March 26, 2006 12:59 PM
> > Subject: Re: [AMRadio] Modulator design needed
> >
> >
> > Mark,
> >
> > Take a look at a Heathkit Apache schematic, (TX-1), for ideas.
> >
> > There is NO driver transformer.  The 5763 driver goes to the Mod
> > transformer
> > and the EL-34s feed it for audio.
> >
> > Bob - N0DGN
> >
> >  -------------- Original message ----------------------
> > From: "W1EOF" <w1eof at hamnutz.com>
> > >
> > > I've been gifted a nice mod transformer so I can build a modulator
> > for my
> > > Johnson 6N2. I don't have a driver transformer so I'm looking for
> > a design
> > > which doesn't need one. I'm sure the schematics are out there, but
> > I keep
> > > finding ones with the driver transformer. Same with all my old
> > radio books
> > > that I've looked at so far. Can someone point me in the direction
> > of a
> > > good
> > > design that is online, or one that you can share with me via
> > email?
> > > Thanks!
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