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SDR: 100 kHz to 4 GHz on a PICe card and other possibilities

MetaFilter says The Phi does for radio what Apple did for computing but that’s just marketing hype for an SDR on a PCIe card. That Phi card costs just a bit under $1000 at Per Vices Corporation. The MetaFilter post also has links to the ARRL digital radio page and one of the comments refers to a Hack-a-Day article Getting started with software defined radio that uses a USB TV tuner and GNU Radio software.

The Phi is also compatible with GNU Radio and includes open source drivers for Linux (only). Two versions are supplied to balance off gain for a higher dynamic range as needed for the ‘real world’ and more gain for less dynamic range such as you might want for a laboratory instrument. Note that it is a transceiver and advertises being able to be used as a wifi hub or a cell phone base. The description lists it as being an SDR with a 100 kHz to 4 GHZ front end but the full specifications indicate it is intended for VHF and higher usage.

As some of the comments note and also as inferred by the dynamic range comments at the Phi website, the receiver is only one part of the system. A good antenna is a must both for gain and for selectivity. One way to reduce the deluge of signals at the front end of the radio is by filtering out those you don’t want to hear. That means an antenna with a reasonable Q and perhaps some input filtering or antenna matching device.

Fldigi (see Southgate) Digital Modes Software runs on nearly any PC and uses the sound card to decode digital modes such as RTTY, PSK31, and others. That is similar in operation to an SDR but has only a 2 kHz input bandwidth to worry about. It has a display to show various aspects of the incoming signal that is being decoded so you can see the sorts of things it is doing. An SDR has a much wider input bandwidth (the Phi claims 200 MHz) and decodes the traditional analog modulation schemes as well as the digital ones.

What it comes down to is that it is all math. Every modulation and encoding scheme can be represented as a mathematical model. All you’ve got to do is to write a computer program for that model to process the digitized input. Unfortunately, that math can get rather complex and the software techniques to do it are not always straightforward. That is where projects like GNU Radio come in. You can let others do the arcane stuff and focus your efforts where best suits you.

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