FW: high power op - modulation and supermodulation

[Mike Langner]

Hello everyone !

Supermodulation and controlled-carrier modulation as used in DX-40, DX-60,
and, interestingly, the Drake TR-3 is actually full carrier during
modulation peaks.  The carrier is controlled so that when there is little to
no modulation (which means there is little to no need for a carrier) the
carrier is dropped far back to avoid over-dissipating the output tube.

A form of controlled-carrier is also used by some very high power AM
shortwave broadcasters, although the depth of the carrier reduction is
usually held to between 3 and 6 dB -- significant if you're paying the power
bill on a 100 to 500 kW transmitter -- or more!!

Reduced carrier was used for years by AT&T for its HF telephone circuits.
There was just enough carrier to synchronize a zero-beated BFO for carrier
re-insertion at the receiving end.  It saved lots of power, lots of heat,
and made the transmission not understandable on a standard AM envelope
detector.

A friend of mine once made a 10 meter hand-held AM transceiver for the old
AM days on 29.6.  The B+ to the final miniature tube was provided by the
modulator via a separate winding on the modulation transformer.  The
separate winding was bridge-rectified and fed to the final back through the
main secondary winding.  Absolutely complete controlled-carrier.  Output
when not speaking was truly zero.  In the days of hand-carried portable
transceivers with a tube final, every possible power economy was necessary.

And then there's the day he fell off the roof of his house while he and I
were talking and ended up painfully in the rosebushes -- but that's another
story.  Oh yes, it was now silent key Ike Meissner, K5CXN who at that time
lived here in Albuquerque, NM.

73 all !!

Mike/
K5MGR
________________


-----Original Message-----
From: Boat Anchor Owners and Collectors List
[mailto:BOATANCHORS at LISTSERV.TEMPE.GOV]On Behalf Of Bry Carling
Sent: Sunday, March 30, 2008 12:26 PM
To: BOATANCHORS at LISTSERV.TEMPE.GOV
Subject: Re: high power op


> Hardly a 'little' bit of carrier!  AM is with full carrier - at full 100%
> modulation

Not necessarily!

Did you ever use AM with reduced carrier?
It is quite popular and still use don the air.

How about AM with "Supermodulation?"
A similar scenario.

The DX60 uses reduced carrier... yes,  just a little carrier!

-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
-----------------------------------------------------------

Subscription control -
http://www.tempe.gov/lists/control.aspx?list=BOATANCHORS
To post - BOATANCHORS at LISTSERV.TEMPE.GOV
Archives - http://listserv.tempe.gov/archives/BOATANCHORS.html

-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
-----------------------------------------------------------

Subscription control - http://www.tempe.gov/lists/control.aspx?list=BOATANCHORS
To post - BOATANCHORS at LISTSERV.TEMPE.GOV
Archives - http://listserv.tempe.gov/archives/BOATANCHORS.html