Overview

Guest host for this session is GPS-expert Joe Jesson, KC2VGL, who will lead us through the basics of GPS-based location and time synchronization technology and circuits.  We'll be exploring applications of GPS in our QRP communications world, with some very interesting projects that can be applied to digital communication modes WSPR and JT65A ... who knows just what options will next appear in the SDR Cube Transceiver?! ;-)

73, George N2APB & Joe N2CX

Audio Recording ... (Listen to the MP3 podcast)

Discussion Notes:

<20:10:23> "George - N2APB": GPS is a 50 bps transmission
<20:14:43> "George - N2APB": Median Earth orbit of 17,000 km
<20:22:21> "George - N2APB": "Time", as reported/computed by the GPS systems is in tight synchronization with UTC time, to the second.
<20:25:32> "George - N2APB": "Correlators" are secret sauce of GPS reception. Series of DFT filters (DSP).
<20:29:11> "Joe N2CX": The correlators act as matched filters based on the known "spreading" data code.
<20:41:55> "Joe N2CX": Gee, with more correlators you could correct for wider time errors!
<20:44:09> "Pete - WB2QLL": Dimension hasn't been updated since 2004
<20:51:22> "Joe N2CX": A GPS-Based Frequency Standard, by Brooks-Shera in QST for July 1998 reference included at the end of the whiteboard.
<20:55:15> "George - N2APB": A"disciplined oscillator" is very similar to a "phase locked loop"-controlled oscillator
<20:56:46> "Joe N2CX": Actually it is quite analogous to the "huff and puff" frequency locked loop technique
<21:00:01> "Joe N2CX": Control of the oscillator in the Brooks Shera is dc to a VCXO!
<21:15:05> "George - N2APB": Wikipedia on NMEA ... http://en.wikipedia.org/wiki/NMEA_0183
<21:17:14> "George - N2APB": eHow on NMEA protocols ... http://www.ehow.com/about_6634469_description-nmea-protocol.html
<21:18:04> "George - N2APB": NMEA Software available ... http://www.softcredible.com/download/nmea/
<21:18:43> "George - N2APB": Advanced NMEA DAata Logger ... http://www.softcredible.com/advanced-nmea-data-logger-download-15422.html
<21:19:48> "Ken - VA3KMD": The uM-FPU from Micromega can directly parse NMEA strings.
<21:20:33> "George - N2APB": uM-FPU? Perfect!! Thanks Ken.
<21:22:51> "George - N2APB": MIT FLEA ... http://www.mitflea.com/
<21:23:41> "George - N2APB": GPS Time and Test 1.5 ... http://www.softcredible.com/gps-time-and-test-download-11880.html
<21:24:22> "George - N2APB": Avangardo GPS Generator PRO 4.0.3 ... http://www.softcredible.com/avangardo-gps-generator-pro-download-17090.html
<21:26:29> "George - N2APB": GPS NMEA application for your iPad ... http://appfinder.lisisoft.com/ipad-iphone-apps/gps-nmea.html
<21:27:15> "Frank N3PUU": great job Joe. Very interesting stuff!

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