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1. Introduction
Thank you for purchasing the QRP Labs QLG1 GPS Receiver kit. This kit will provide a highly sensitive,
highly accurate GPS receiver module, using the popular MediaTek chipset. This chipset features high
sensitivity (as good, or better, than any other popular chipset) and an extremely accurate 1pps time pulse
(10ns rms). The kit features provide a number of advantages compared to using a ready-built GPS
module:
1) A kit – fun and educational to build – easy construction with no SMD components
2) High sensitivity: the large ground plane area provides an additional 7.5dBic of antenna gain,
compared to a typical patch antenna arrangement in which the PCB is the same size as the patch
3) Built-in patch antenna, or the ability to connect your own external antenna via SMA if you wish
4) Hobbyist-friendly, 0.1-inch pitch connections
5) Three on-board LEDs provide a visual indication of what is going on
6) Proper 5V level conversion, no need for any pull-up resistors
7) Direct connection to QRP Labs kits by shielded cable, no need for pull-ups or capacitors
2. Antenna
The QLG1 GPS receiver kit can be built with two antenna options: either an on-board patch antenna, or an
externally mounted active antenna (with SMA connector). The module can supply a regulated voltage
suitable for powering the external antenna. The external antenna option may be useful if you wish to
mount the antenna separately to the module; furthermore active external antennas typically provide the
highest receive sensitivity. This may be useful in particularly challenging locations. However, the supplied
custom-tuned patch antenna is already highly sensitive and will be suitable for most situations.
Antenna gain
This chart of antenna gain vs size of the
square ground plane dimension, is extracted
from the manufacturer's datasheet.
The QLG1 PCB is sized 3.6 x 2.5 inches (91
x 64mm). The right hand side of the PCB is
used for the voltage regulator and level
converter circuits. In this way, the patch
antenna is mounted on the reverse of the
PCB, in the middle of a virtually un-
interrupted ground-plane 64 x 64mm. This is
indicated on the chart by the red line. You will
note that it provides 7.5dBic gain over a more
typical 30 x 30mm0sized ground-plane. This
is an important feature of the QLG1 kit, providing high sensitivity!
QLG1 GPS Receiver kit
1
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Related Manuals for QRP Labs QLG1
Summary of Contents for QRP Labs QLG1
- Page 1 7) Direct connection to QRP Labs kits by shielded cable, no need for pull-ups or capacitors 2. Antenna The QLG1 GPS receiver kit can be built with two antenna options: either an on-board patch antenna, or an externally mounted active antenna (with SMA connector). The module can supply a regulated voltage suitable for powering the external antenna.
- Page 2 3. Design The design is quite simple. Note the circuit diagram above. The GPS receiver RF module does all the hard work. The additional circuits are supply filtering, voltage regulation (the module requires 3.3V operation), level shifting, and LED indication. Supply voltage filtering is undertaken by two 0.1uH inductors in series with both the +5V and ground supplies, and plenty of smoothing/decoupling capacitors (the 0.1uF and 22uF capacitors).
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Page 3: Parts List
4. Parts List 4.1 Resistors (may be supplied either with 4-band or 5-band colour codes, see below) 1K resistor (brown-black-red-gold OR brown-black-black-brown-brown) 1K resistor (brown-black-red-gold OR brown-black-black-brown-brown) 470-ohm resistor (yellow-purple-brown-gold OR yellow-purple-black-black-brown) 470-ohm resistor (yellow-purple-brown-gold OR yellow-purple-black-black-brown) 470-ohm resistor (yellow-purple-brown-gold OR yellow-purple-black-black-brown) 1K resistor (brown-black-red-gold OR brown-black-black-brown-brown) 560-ohm resistor (green-blue-brown-gold OR green-blue-black-black-brown) 470-ohm resistor (yellow-purple-brown-gold OR yellow-purple-black-black-brown) - Page 4 PCB. The QLG1 PCB has a ground plane on both sides of the board. Component connections to the ground plane need a little extra heat, because of the heat dissipation of the ground plane.
- Page 5 The order of construction is not important. However, a good principle to follow is to install the smaller components first, so that the larger ones do not prevent easy access. In the following photograph, all the resistors, capacitors, inductors, LM317LZ voltage regulator (3-pin TO92 package), 74ACT08 chip, and 3.6V zener diode have been fitted.
- Page 6 LEDs It is critical of course, to ensure correct LED orientation. The cathode of the LEDs is indicated by the flat on the body of the LED. However, on 3mm LEDs the “flat” is not so easy to see (though quite clear, using magnification). So note that the cathode is also indicated by the shorter wire (before you’ve cut them!) and also by the larger electrode.
- Page 7 The patch antenna connection pin is not in the exact centre of the square patch. Please refer to the photograph (above). The connection pin should be furthest away from the through-hole components section of the PCB, as shown. The patch should be positioned on the solder side of the PCB.
- Page 8 QLG1. The order of connection pads on the QLG1 is also the same as those on the U3S. Note that the QLG1 TXD (output) signal connects to the U3S RXD signal (input). The cable shield should be connected to ground at...
- Page 9 0.5 seconds (varies depending on data payload). Default Baud Rate The default baud rate of the QLG1 is 9,600 baud. This is compatible with the default settings of the Ultimate3S QRSS/WSPR TX kit (and other QRP Labs products). The list of default NMEA sentences is described in a later section.
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Page 10: Version History
NMEA sentence structure. Finally, please join the QRP Labs YahooGroups forum, if you have not already. The forum members can provide support for any questions regarding issues, and share your success stories too.
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