Most SSB capable transceivers, that can also transmit in AM mode, do so
using the same balanced modulator that they use to produce DSB. When in
SSB mode the DSB output of the balanced modulator is run to a filter to
reject the unwanted sideband. When transmitting in AM mode the filter is
usually bypassed to allow both sidebands to be transmitted, and the
modulator is either unbalanced to let carrier through, or the carrier is
reinserted in a later stage.
Some transceivers ( such as the Kenwood TS-440 ) have independent
control of TX audio level and carrier level, so that when AM mode is
selected you can be transmitting anything from DSB with virtually no
carrier (requiring the receiving station to have his BFO on, and zero
beat to your suppressed carrier) to full carrier level AM, or even just
a carrier with no sidebands at all, depending on how you adjust the
controls.
Some transceivers ( such as the Kenwood TS-50 ) have preset carrier
level when selecting AM transmit mode, so that DSB with no carrier is
not an option.
A very few transceivers ( such as the Ten-Tec 586 Paragon II, and I
don't know of another ) when transmitting in AM mode generate a DSB
signal with their balanced modulator, filter it to remove one sideband,
and reinsert the carrier, producing "SSB AM" rather than "real DSB AM".
With the Paragon II you can select which sideband you want to transmit,
and both sidebands (DSB) is not an option. When receiving AM with the
585 Paragon or 586 Paragon II, you can listen to either sideband or both
sidebands, depending on the IF filter you select and the setting of the
VFO and Passband Tuning controls.
The 585 Paragon cannot transmit AM in any form (other than SSB with no
carrier), only the 586 Paragon has AM TX capability.
DE N6KB
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