Modulation impact when amplifying a DSB signal?

Wilson Lamb infomet at EMBARQMAIL.COM
Mon Feb 16 11:26:31 EST 2009

Here's the 7360 rating, the upper of the two.  It won't do your 5W, but will 
drive the pants off anything up to 6146 or so.
----- Original Message ----- 
From: "Wilson Lamb" <infomet at>
To: "Wilson Lamb" <infomet at>; <doc at>; 
Sent: Monday, February 16, 2009 10:45 AM
Subject: Re: Modulation impact when amplifying a DSB signal?

> Well, that's interesting.  Why the low voltage?  Batteries??  All these
>> circuits will work better at higher voltage.  5W input is 40mA and 5W 
>> output will take twice that, I expect.  If you are talking PEP, then much 
>> more. That's a lot for the small tubes.
>> The high level balanced modulator is the way to go for DSB, avoiding the 
>> amplifier problem.  I remember the 7360 tube which was made for this, but 
>> don't think it went to 5W...look it up.  There used to be lots of 7360 
>> circuits in the Handbook and QST.  With the full QST archive on the ARRL 
>> website, reference work has been facilitated dramatically!  If filament 
>> power is not a big problem, any two RF  tubes would do.  6AQ5s are 
>> cheaper than dirt and would do it easily.  Going farther back, a pair of 
>> 6AG7s would be great, in octal sockets.
>> I have circuitry froom the 30s doing it with a pair of 6V6s, probably 
>> fine at least to 40 meters. You could keep the filaments of the TX off 
>> most of the time, just turning on during contacts.
>> To go fully retro, you could find an old Vibrapack for the HV, or build 
>> your own.  Vibrators are available at many hamfests and on many websites. 
>> Who knows, you might get to 10W, which would be a pretty useful SSB 
>> signal!
>> But I'd encourage you to bite the bullet and go SSB, maybe learn some 
>> circuitry along the way.  When I was in grad school, I built a 50KHz 
>> acoustic command link for use in the sea.  It was SSB, phasing method, 
>> and worked great.  I could go thousands of feet in water, never got to 
>> max range, and it worked fine as RF around the lab.  I tested it by 
>> running an FM radio through it and casual listeners coming by the lab 
>> didn't notice I wasn't listening to the usual radio.
>> The phasing was done with the Dome network, as used by B&W in their 
>> commercial product.  I simply copied their circuit and used opamps 
>> instead of tubes.  My carrier phase shift was done with two ten cent 
>> transistors and simple RC lead/lag elements.  I could give you the 
>> schematics for all this. I may even have a set of the RC components for 
>> the network.  The idea of produciing a nice SSB signal with a couple of 
>> 9V batteries is pretty appealing!  So is the idea of a whole rig running 
>> on a little gel cell or plugging into any car dashboard!  I'm about to 
>> embark on a qrp project myself, but probably CW only for 
>> now...backpacking.
>> Please tell us more about your objectives.
>> 73,
>> Wilson
>> W4BOH

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