[Boatanchors] SSB and carrier insertion?

[Gary Schafer]

As Glen said "it is a technical definition thing". There are many modes 
of SSB. To be technically called SSB as hams know it, the carrier will 
be down 40 db. This mode is called suppressed carrier.

  There is a mode of SSB that is called reduced carrier. It has a 
different designator but is still called SSB. If I remember right the 
carrier was usually down about 16 db. This was used to have a reference 
to lock a receiver to the signal.

Then there is SSB with full carrier, also known as AME. AM equivalent. 
This mode was used extensively in the marine bands during the transition 
between AM and SSB. This allowed the SSB station to transmit a signal 
that could be copied by an AM receiver. As most of the SSB transmitters 
were of the filter type, it would have been more difficult for them to 
transmit both side bands.

SSB AM does not have quite the audio punch that full AM does. Without 
the other side band the detected audio at the receiver is 6 db down from 
what a double side band AM signal would be. There is 3 db less audio 
power being transmitted and the detector has another 3 db of loss not 
having the coherent other side band present to add in the detector.

The detector in the receiver will also have more distortion as 
modulation approaches 100% with single side band AM from what it will 
with double side band AM. This is why it sounds a little funny compared 
to full AM. In essence the detector gets confused as to whether the 
audio is modulating the carrier or the carrier is modulating the audio 
signal.

When operating SSB with carrier or double side band with carrier, with a 
side band transmitter the carrier needs to be reduced 6 db in order for 
it to operate properly. This allows the amplifier in the transmitter to 
achieve the peaks of the audio power.

A normal AM transmitter has audio peak power 6 db higher than the 
carrier (4 times the power)

All of these modes are perfectly legal.

73
Gary  K4FMX


rkerr wrote:
> SSB with carrier is not illegal.  The Heath HX-10 Marauder and the 
> Collins KWS-1 were designed with the capability of generating SSB with 
> carrier.
> 
> The only advantages to doing this are 1) it allows a rig that was 
> primarily designed as a SSB - suppressed carrier system to transmit an 
> AM mode with carrier, which is detectable by AM receivers using envelope 
> detectors, without extensive modifications and 2) the signal takes up 
> less bandwidth than a DSB with carrier signal.
> 
> This mode is quite inefficient, with respect to conversion of DC input 
> power to useful RF output power, since the RF power amplifier must be 
> run in Class A or AB, rather than the more efficient Class C of a plate 
> modulated AM rig, in order to maintian linearity.  In addition, you only 
> achieve half the transmitted information power of a DSB signal with the 
> same carrier power.  The SSB with carrier signal is somewhat more 
> susceptible to HF fading than a DSB with carrier signal is.
> 
> Bob
> WB4TGG
> 
> James M. Walker wrote:
> 
>> Naw,
>> not illegal, MY Central Electronics 10A, 10B and 20A all do it that way.
>> Jim
>> WB2FCN
>>
>> ----- Original Message -----
>> From: "Eugene Hertz" <ehertz at tcaf.org>
>> To: <boatanchors at mailman.qth.net>
>> Sent: Monday, March 14, 2005 1:56 PM
>> Subject: [Boatanchors] SSB and carrier insertion?
>>
>>
>> Here's my question. I've begun studying for my general and I read in the
>> arrl book that inserting a carrier with one side band in not a legal
>> emission. Is that right? Could I have misread this? If I read that right,
>> can anyone explain why if DSB with carrier (am) is allowed and LSB and 
>> USB
>> without carrier, why wouldnt LSB-C or USB-C (with carrier) be allowed?
>>
>> As soon as I get my general and code passed, my transmitter is a central
>> electronics 100V (courtesy W0YVA). This radio has SSB and also SSB with
>> carrier inserted modes (also has PM, AM, FSK, you name it!) and I 
>> began to
>> wonder was this kind of emission legal at one time (radio was made around
>> 1959) ? Does any one know when/why it became illegal?
>>
>> Also, what would be the benefit of running SSB with carrier? Does it make
>> the signal more easily detected? say, without the need for a product
>> detector, but just a BFO?
>>
>> Thanks in advance (for being patient with all my questions!)
>> Eugene
>> KC2NWG
>>
>>
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>>
> 
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>