K3 ESSB

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ESSB

Extended Single Sideband - A modulated transmission voice mode of J3E SSB that exceeds the audio bandwidth of standard or traditional J3E SSB modes in order to support the fidelity required and desired for relative high fidelity, full range clean and articulate vocal audio.

Generally used for Hi-fidelity amateur radio phone transmissions where maximum speech intelligibility is needed or desired.

ESSB Hi-fi has many benefits, the most noticeable being a very pleasing and highly defined sound not inherent with traditional SSB audio. Also, ESSB only occupies 1/2 of the bandwidth required by AM transmissions for the same audio quality, since SSB is a Single Sideband Suppressed Carrier mode vs. AM, which is a Double Sideband with Carrier mode.

There is a TX ESSB menu entry in the K3 for enabling ESSB and setting the tx bandwidth (3.0, 3.5, 4.0Khz). There are currently no user adjustments to shift the passband up/down in frequency, but on January 23, 2008 Lyle KK7P reported to the Elecraft reflector: "The default Tx Audio passband is 250 Hz to 3150 Hz. Its adjustment is not yet part of the user interface, but will be."


Requirement for KFL3A-6K 6 kHz Filter

According to the FAQ, the K3 is capable of ESSB provided the optional 6 kHz filter is installed. Here's the explanation provided by Lyle KK7P on why the KFL3B-FM filter can't be used for ESSB or AM transmitting: 

Unlike most DSP-based radios, the K3 converts from the main IF (8.215 MHz) to the 15 kHz DSP IF without
an intervening 455 kHz IF.  This helps give the K3 a cleaner sound and better dynamic range since there 
are fewer conversions. However, this also means the IF crystal filter must have exceptional skirt selectivity 
to prevent the 15 kHz "image" from getting through.

In FM mode, capture effect helps suppress the effect of "image" leakage.  AM and (E)SSB modes have far 
more dynamic range and the 15 kHz IF image must be suppressed by some 10s of dB more than is required for 
excellent FM operation.

It is for this reason that the FM filter is recommended only for FM use. It may also be used for AM receive, 
but is not recommended for AM transmit.  The 6 kHz filter has the necessary 15 kHz IF image rejection 
to be suitable for use with either AM or (E)SSB.

External Links

What is Lo-Fi - Mid-Fi - Hi-Fi and ESSB? - NU9N

K3 ESSB TX Passband Spectra - at bottom of N1EU's K3 page

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