[AMRadio] Re: Modulator design needed


ne1s ne1s at neandertech.com
Mon Mar 27 13:05:51 EST 2006


While other tubes may do better, I've had good luck using AB1 807s in 
VikingI/II/DX-100 class transmitters - they'll do 100% cleanly. 

 -Larry/NE1S 

Gary Schafer writes:
> 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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>  
> 
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