Modulation impact when amplifying a DSB signal?
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 embarqmail.com>
To: "Wilson Lamb" <infomet at embarqmail.com>; <doc at kd4e.com>;
<BOATANCHORS at LISTS.TEMPE.GOV>
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
>> 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
>> Please tell us more about your objectives.
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