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NU9N The Carrier Phenomena

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NU9N The Carrier Phenomena

Сообщение EW1MM » 16 апр 2024, 22:30

NU9N John.
The Carrier Phenomena.

There are evidently some folks on the air who have been reporting that some of the "hi-fi" guys have a carrier in their audio as a result of their wide bandwidths. I just want to briefly address this issue and discard any notion that this is happening as a result of any external or internal processing, bandwidth or any low frequencies below 80Hz that are being fed to the transmitter.

When an SSB station has a relatively wide audio response and is modulating frequencies at or below 100Hz, an interesting phenomena takes place.
When tuning off-frequency on such a given station, the listener may perceive what he/she thinks is a carrier.

For example, if you are listening to someone on USB, and tune down frequency by about 500Hz,
if the transmitting station is modulating 100Hz with any energy, then you will hear apparent tones at 600Hz.
But, ONLY when they are talking!

This is NOT a carrier that is being heard, but the 100Hz tone in the voice being off-beated up by 500Hz resulting in 600Hz tones via modulation.
The reason that this phenomena is not usually noticed as much on the average narrow-band SSB signal, is because there is not enough low frequency energy to bring up to a higher pitch to start with.

Just in case some believe that hi-fi audio effects a transmitter's carrier suppression, that's a hoax!
The audio that you feed to the transmitter has NOTHING at all to do with the carrier suppression adjustments in a transmitter, especially with the newer DSP controlled rigs!

If a hi-fi station keys the mic but does not talk, and their background noise is suppressed sufficiently, you should hear no carrier sounds at all.
If you do hear a carrier while they are not modulating, then they may have a carrier suppression problem.
But that is a totally separate issue from their audio being fed to their transmitter.
A transmitter carrier suppression problem will still be evident even if the mic input signal is disconnected!

Most modern DSP controlled transceivers like the Kenwood TS-950SDX,TS- 870S, TS- 850/DSP-100, Icom 756 Pro, Yaesu FT-1000MP etc... have transmitter carrier suppression figures better than -60dB or more!

The End.

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