[AMRadio] Rothman Modulation


k0ng at inebraska.com k0ng at inebraska.com
Wed Dec 22 20:32:13 EST 2004


There was a Rothman circuit, worked well but I would not use it today.
The tube in the antenna lead could generate harmonics without a low pass
filter, at the band of operation.

Mike was correct, Taylor Modulation did and does exist, dont tell the
collectors but I modified an ARC-5 for Taylor. Uses one final, modulated
by a single 829B.Not currently on the air but available.

73 Charlie, K0NG

Quoting David Knepper <cra at floodcity.net>:

> Wasn't there a commercial modulator using the "Rothman" circuit some years
> ago.  I remember seeing it somewhere in a catalog.
> 
> 
> Dave, W3ST
> Publisher of the Collins Journal
> Secretary to the Collins Radio Association
> www.collinsra.com
> Nets:  3805 Khz, Monday/Wednesdays 8 PM EDST
>           14250 Khz Saturday, 12 Noon EDST
> 
> ----- Original Message -----
> From: "Geoff/W5OMR" <w5omr at w5omr.shacknet.nu>
> To: <amradio at mailman.qth.net>
> Sent: Wednesday, December 22, 2004 11:24 AM
> Subject: [AMRadio] Rothman Modulation
> 
> 
> > This is a new term, for me.  So, a Googling I went.
> >
> > Not much information on Rothman Modulation, but there was some.
> > Perhaps someone else on here can add to this?
> >
> > 73 = Best Regards,
> > -Geoff/W5OMR
> >
> > --------------------------------------------------------------
> > Article: 101889 of rec.radio.amateur.boatanchors
> > From: Edward Knobloch <alias at nowhere.net>
> > Subject: Re: Info needed on "Taylor Modulation" from the 50's.
> > References: <shcin090tfr8ge013ac7b8e9sdifljiav1 at 4ax.com>
> > Message-ID: <J6bed.360$Ae3.55 at trndny02>
> > Date: Fri, 22 Oct 2004 17:06:49 GMT
> >
> > Mike Baker <k7ddmjb at qwset.net> wrote:
> > > Hello to all.
> > > When I was a kid I recall reading something in an old CQ/73/QST
> > > magazine about a modulation method for AM called Tayor Modulation.  It
> > > was sort of a precursor to controlled carrier and used a seperate
> > > modulator tube hooked up sort of in parallel to the final amp and
> > > usually was the same tube type.  There was no modulation transformer
> > > like in typical class B High level modulation schemes.
> > <snip>
> >
> > Hi, Mike
> >
> > You are thinking of "Rothman Modulation" April 1952 CQ.
> > (Which I can't find).  If I recall correctly, controlled
> > carrier screen voltage for the finals was derived from the rf output
> > carrier power.  I remember a picture of an outboard box with a couple
> > of 6Y6 style tubes (perhaps it was a single 6Y6 and a rectifier tube),
> > modulating a pair of 813's.
> >
> > 73,
> > Ed Knobloch
> > ---------------------------------------------------
> >
> > and the reply was...
> >
> > ---------------------------------------------------
> >
> > Article: 101890 of rec.radio.amateur.boatanchors
> > From: "COLIN LAMB" <k7fm at teleport.com>
> > References: <shcin090tfr8ge013ac7b8e9sdifljiav1 at 4ax.com>
> > <J6bed.360$Ae3.55 at trndny02>
> > Subject: Re: Info needed on "Taylor Modulation" from the 50's.
> > Message-ID: <zZbed.4367$KJ6.1794 at newsread1.news.pas.earthlink.net>
> > Date: Fri, 22 Oct 2004 18:05:19 GMT
> >
> > Hello Ed:
> >
> > My wife says I have so much crap I could not possibly find anything - but
> I
> > walked right to the shelf where the April 1952 CQ magazine was.
> >
> > You are therefore batting 1 for 3, since you got it right on the outboard
> > chassis, but wrong on the 6Y6 style tube.  However, when you get to be our
> > age and have forgotten more circuits than the younger hams have ever read
> > about, that is not that bad.
> >
> > Anyway, there were two different circuits shown.  A 100 watt mobile
> > modulator using a 6X4 rf rectifier with a 6SN7 modulator tube, and a fixed
> > station modulator for up to 1000 watts uisng an 80 rf rectifier, a 6SL7
> > speech amp and a 6CD6 modulator tube.  Since the 6CD6 tube has a plate
> cap,
> > it does not look like a 6Y6.  The 6BQ6 and 6BG6 can also be used.
> >
> > I have a number of 6CD6 and 6BG6 tubes and never could figure out what to
> do
> > with them.  This is the answer.  Build dozens of Rothman modulators.
> >
> > I think later that year and into 1953, you could buy an "efficiency
> > Modulator" using this system.  They claimed 70% efficiency, which was much
> > better than the 52% efficiency of high level plate modulation.
> >
> > And my wife thinks I cannot find things.  Ha.
> >
> > 73,  Colin  K7FM
> > -----------------------------------------------------------------
> >
> >
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