[AMRadio] Rothman Modulation


Bob Bruhns bbruhns at erols.com
Wed Dec 22 11:13:15 EST 2004


I saw some stuff too... if I understood, Rothman and others are
experimenting with FM on a room-temperature laser to get precise
spectrographic readings from low-cost gear.  Kind of scientific ham stuff.

  Bacon, WA3WDR


----- Original Message ----- 
From: "Geoff/W5OMR" <w5omr at w5omr.shacknet.nu>
To: <amradio at mailman.qth.net>
Sent: Wednesday, December 22, 2004 10:24 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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