http://elecraft.85.s1.nabble.com/K3-Revolutionary-Noise-Reduction-tp2567008p2568131.html
> K3 - Revolutionary Noise Reduction
>
> It was announced today, by Professor Morsig at the Institute of
> Ljubljana, that the K3 has been chosen to test a revolutionary new
> approach to combating receiver noise and improving HF reception.
> The basic principal behind this approach is the shifting in
> frequency of noise by a few mHz (that's milli-hertz) away from the
> tuned
> frequency. This in effect produces a hole in the noise spectrum where
> weaker signals may be detected. The residual noise is directly
> proportional to the bandwidth of the hole. Therefore, for wider
> signals,
> such as SSB, a modified approach is required. The hole is moved
> progressively over the required signals bandwidth and the signal is
> sampled at each step and integrated to reproduce the original wideband
> signal.
> A second feature associated with this algorithm deals with
> variations in propagation. We all know that propagation is largely
> dependent on the solar flux. Propagation is changed due to the effects
> of the solar wind. A little known fact is that the remnants of the
> solar
> wind that reach the receive antenna modulates the noise. When the
> noise
> is detected this modulation can be interpreted to give information
> about
> the condition of the D, E and F layers. This can be used to produce a
> real-time table of MUF and critical frequencies for each layer. At
> night
> some kind of remote sensing with suitable location corrections has
> to be
> used.
> The third and more revolutionary feature, which depends heavily on
> the previous features, involves the generation and use of virtual
> transceivers or individual ionosphere layer repeaters. As an example
> we
> will assume a distant CW signal is transmitted on 21.110Mhz and the
> MUF
> is around 15.000Mhz. The signal will not be refracted to our receiving
> station and most of it is lost in space. If we transmit a heterodyning
> carrier pulse on 14.110MHz, which is below the MUF, then it will mix
> with the transmitted signal and produce a weak signal pulse at
> 7.000MHz
> which is reflected back to the receiving station. There is a time
> delay
> between the sending of the pulse and receiving the return pulse. The
> transmitted pulse length is made less than this delay so that the
> 7.000MHz return pulse may be received between transmit pulses. This
> process is repeated and the received signals integrated to
> reconstitute
> the original signal sent.
> There are some operating problems to be worked out with the
> transmission of multiple heterodyning carriers. Thus only a few K3's
> are
> expected be loaded with the new firmware until these problems are
> resolved (spread spectrum has been suggested).
> New menu items may be added to include these features in a future
> K3 DSP firmware update. MUF OFF/AUTO and 1-10 will vary the effect of
> received signals using simulated MUF values. This can improve
> signals on
> all bands. Unfortunately this enhancement is not reciprocal and only
> works on receive. Thus K3 to K3 contacts should have a distinct
> advantage. The algorithms used are not open source as these features
> are
> expected to have a huge affect on the whole radio communications
> industry. It is still in the early beta-test stages.
>
> The above is a rough summary of the original unwinese language
> document submitted by Professor G. E. T. Morsig who is the 1st
> Associate
> Professor of Radio at the Institute of Ljubljana. He will be very
> interested in your assessment of this system and may be contacted via
> F(zero)OL (qrz.com).
>
> My apologies if I have made a minor slip or two in the
> translation.
> Unwinese is not an easy language to translate.
>
> Please do not contact Elecraft for this firmware until there is an
> official statement!
>
> 73 and Enjoy
> Tony Fegan VE3QF (anxiously awaiting further developments!)
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