software changes rather than by adding new hardware. This ensures that the K4 can take advantage
of new modes, bands, or other features in the future. Since it uses direct sampling, signals are
digitized right at the receiver inputs, and the transmitter's amplifier chain is also driven by a digitized
signal. Older SDR architectures digitized signals at a low intermediate frequency (IF), resulting in
poor suppressions of down-conversion or up-conversion images.
There are three models: the basic K4, with one set of receive filters and one analog-to-digital
converter (ADC); the K4D, with a second set of receive filters and a second ADC; and the K4HD,
which adds a superheterodyne front end that can be enabled as needed to provide even greater
dynamic range. The superhet module uses high-performance, narrow-band crystal filters such as
those used in the Elecraft K3S.
Even the basic K4 provides simultaneous dual receive on the same or different bands/modes.
However, the K4D and K4HD models include an additional receiver module (KRX4) with a second set
of band-pass filters, improving signal handling during dual-receive operation on different bands. The
second receiver also permits diversity reception, i.e., the use of different antennas for the two
receivers to counteract fading (QSB).
A basic K4 can be upgraded to a K4D by installing the KRX4 option. Similarly, a K4D can be
upgraded to a K4HD by installing a KHDR4 module. Other internal options and external accessories
are applicable to all three models, including a wide-range ATU (KAT4), MH4 microphone, SP4
external speaker (1 or 2). For further information, visit www.elecraft.com.
INSTALLATION INSTRUCTIONS
CAUTION: Ground your K4 properly before operation using the provided wing nut ("GND"). For
suggestions, see www.arrl.org/grounding.
Even though the K4 has extensive internal protective circuitry, external protection against lightning
strikes is strongly recommended, especially in lightning-prone areas.
