Recall I was daydreaming about probe antenna arrays. In my daydream I cooked up a situation where instead of coaxial phasing boxes and delay lines you use SDR receivers and some kind of protocol to time mark each packet of sampled information. With this kind of antenna you would have virtually complete control over where your antenna points, and where your nulls occur. You could even do multi-multi arrays, and for a very wide band width of frequencies. The problem with this idea is accurately giving each packet of I/Q data a time stamp.
Bob N4HY put on the reflector some information about a German ham group who was preparing for interplanetary ham communications. This in itself is an amazing thing to contemplate, especially for an old geezer like me who is stuck on 160M and 80M.
What kind of hardware are the Germans using? Why soft hardware of course!!!! SDR and BIG HONKIN ANTENNAS. They are using the SDR-IQ from RF Space.
I was poking around the RF Space website and lookie what I found!!
Here are some of the specs
PRELIMINARY Frequency Range: 0.01 - 32 MHz * Digital Down Converter: Xilinx XC3S500E PC Interface: Ethernet 100 base-T (UDP/TCP/IP) Filters: 32 bit ,120+ dB 90% Alias Free BW Decimation Rate: Variable 70-2047 Output Sample Rate: 39 KHz to 1.15 MHz @ 24b IQ Flatness: <0.1> Dynamic Range: 105 dB MDS: -132dBm in 500 Hz BW Analog to Digital Converter: 16bit w/ Dither Preselection: 10 Filters Attenuators: 0, -10dB, -20dB, -30dB Sample Rate: 80 MHz Memory: 65536 x 16 bit samples External Radio Control: Built-in RS-232 port Dimensions: 210 x 70 x 180 mm Display: 16 x 2 Character LED LCD Power: 5 Volts DC @ 1.5 Amp ** Connections: 4 x BNC (RF In, Ext Ref, Trigger, IF Out) , RS-232, Pulse Out, Ethernet, Power. Expansion: Internal Downconverter, Internal 10 MHz Phase/Frequency Lock. Price (base configuration): Estimated MSRP $2999.00, EURO 2250
$2999 You might say ARE YOU NUTZ!!! Well I just may be nutz, BUT It proves the concept.
Here is the exciting part:
The SDR-IP can be configured with a ultra low phase noise encode clock option (REF-ULN). This oscillator can be locked to reference clocks like GPS and Cesium standards. A trigger option allows the synchronization of multiple SDR-IP receivers to trigger signals or 1PPS pulses from GPS to within ~50nS. This allows many SDR-IP receivers to be used in radio holography, direction finding, interferometry and radar applications. The ethernet I/Q data is serialized so that streams from multiple receivers can be processed coherently (processing software not supplied). When not externally locked, the optional oscillator has a stability of +/- 1 ppm over temperature. The phase noise at 10 KHz is -170 dBc/Hz typical.
Eventually the cost will come down. This unit uses a very advanced A/D which samples the entire Spectrum all at once. The protocol is TCP/IP, on an intranet. Time Stamp? How about buying a few closed out GPS receivers. You could even use the GPS to accurately mark the location of the probe antennas for software analysis.
You can say " but but but this is so expensive and complicated...." You need 20-30 acres for a bunch of beverages. How much does that cost? With a system like this you could build one big tower in the middle of the property make a 4 square of wire transmitting verticals or 3 el parasitic arays, and have a very elaborate receiving array/s probably on 3 to 5 acres. Cheap in comparison to 30 acres AND more versatile. With this kind of setup you can optimize the TX antenna for best gain, and you can optimize the RX antenna for best pattern, hence best of both worlds.
Hmmm it said RADAR and holographic applications.... I wonder how you call CQ on RADAR or a holographic QRZ? I know what 3 dimensional radio looks like since I own one but how does 3 dimensional holographic radio look?
I wonder if we could use the hologram to generate a virtual KNOB?
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