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Re: Using Class C Amplifiers for SSB



Adding a modulated carrier (effectively not suppressing the carrier out of
your rig) to an SSB signal essentially makes it an AM signal.  After all the
full name of the mode is single-sideband suppressed carrier.  OK, OK, you'd
need the other sideband to make it fully AM.  For an amplitide modulated
signal of any kind, the transistors in a Class C amp will be turned off for
most of the RF cycle.  So adding a modulated carrier to the SSB signal will
still not prevent the amplifier from going into cuttoff away from the
modulation peaks.

Now I suppose, you could insert an unmodulated carrier into your signal that
would in effect be a CW tone that is always there regardless of your
modulation.  However, then you'd always have that tone in your transmitted
signal which would probably be annoying to those listening as well (same
goes if you have the carrier modulated or unmodulated actually).  OK, so
they could notch it out.

And as Joe, says, adding a carrier will end up increasing the duty cycle.
Sure, no problem on the terrestrial end, but it will create more dissipation
on AO-40.  So I would discourage this as well.

73,

Jon
NA9D
 
on 1/1/01 3:03 PM, Joseph V Murray at k0vty@juno.com wrote:

> I suggest that the greater the carrier inserted the greater the duty
> cycle and the greater the power used by AO-40.     That is why FM is a no
> no.    I have no Idea what the SSB audio would sound like .
> 
> Joe K0VTY
> ======
> 
> 
> On Sun, 31 Dec 2000 15:52:53 -0700 "James R. Duffey" <jamesd1@flash.net>
> writes:
>> I recall that Joe Riesert, W1JR, writing in his old VHF/UHF column in Ham
>> Radio suggested that Class C amplifiers could be used for linear applications
>> like SSB by injecting a bit of carrier into the drive signal. The carrier was
>> enough to bias the amplifier into linear operation. As I remember the amount
>> of carrier required was low, more than 10 dB down from the signal. Has
>> anybody tried this? It may be a way to use the "Pod" amps that are being
>> discussed. - Dr. Megacycle KK6MC/5


-------------------------------------
Jon Ogden
NA9D (ex: KE9NA)

Member:  ARRL, AMSAT, DXCC, NRA

http://www.qsl.net/ke9na

"A life lived in fear is a life half lived."

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