CW Skimmer

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CW Skimmer, which was publicly announced in February, 2008, is shareware available from VE3NEA at []. CW Skimmer enables CW operators to be aware of everything that is going on across large swaths of any band. It copies signals across an entire band. and decodes, validates, and lists callsigns with their associated frequency. The latest current release is Version 1.4. After a full-featured 30-day trial period, a license costs US$75.

There are three basic modes of operation with CW Skimmer. Most people will start by simply listening on their current transceiver, with the widest available filter. Typically, that will let Skimmer hear 2-3 KHz of spectrum. Tune to a frequency with activity (a DX pileup, for example) and you’ll see each of the stations represented by a horizontal line of dots and dashes on the waterfall display. As it identifies stations and other message content of interest it “flags” these for you.

The second mode is using a Software Defined Receiver to receive the band directly. Using this approach permits receiving an entire band- up to at leasty 192 KHz with the right computer and sound card.

The following is a sample of CW Skimmer at work on 40 meters with a [ SoftRock]. It was “listening” to a brief period of a recent CQWW CW and decoding what it saw. The first figure shows the main screen. The waterfall display only shows about 5 KHz from the center frequency of the principal decoder (the green zone at the bottom), but in fact, the SoftRock is receiving the entire slice of spectrum that the soundcard can handle. In this case, 326 different signals (or possible signals) were being copied across the band, and 154 calls were identified in less than 2 minutes (figure 2). The callsign list is dynamic – stations are constantly being added or dropped when they are no longer there.

Skimmer Fig1.jpg Skimmer Fig2.jpg

The third mode of operation involves configuring an SDR to work off the first IF of a receiver, before the usual selectivity-defining filters. Some surgery will generally be required, but some radios, notably the Elecraft K3, make a wideband IF output available. with the advent of the [ LP-PAN], a special-purpose SDR that is designed specifically to work with the K3, a number of K3 owners have adopted this approach. The principal disadvantage is that CW Skimmer will only display 24 KHz of spectrum at a time in this mode - VE3NEA has said that this limitation is inherent to the software design, and cannot be changed.

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