OpenStint

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Simple setup with RTL-SDR ​

This is the most simple setup imaginable. You need your laptop, and the following hardware:

PartApprox. Cost
RTL-SDR Blog v4$40
1:9 HF balun$2
10m/30ft RG316 coax SMA Male To SMA Male$15
10m 20AWG silicone-insulated wire$5
1m USB extension cable$2
390 Ohm resistor$1
TOTAL$65

Your prices might vary (shipping and taxes).

You'll also need transponders:

  • openstint-transpoder is a DIY open-source alternative. Go to JLCPCB for larger quantities (40pcs/$200, 80pcs/$300). For smaller quantities, ask around on rctech forum - see purchase options.
  • AMB RC3 (EOL), MyLaps RC4 ($100) and RC4-Hybrid ($150), as well as MRT mPTX ($70) and other RC3-clones are supported.
  • RCHourGlass transponders are also supported.

System diagram ​

+-------------------+
|                   |   +--------+          +---------+         +---------+
+---------+  Loop    \--| 1:9 HF |          | RTL-SDR |         | Windows |
| 390 Ohm |  Antenna /--| balun  |--[coax]--|   v4.   |--[usb]--| Laptop  |
+---------+         |   +--------+          +---------+         +---------+
|                   |
+-------------------+

Some explanation:

  • Lay down the loop as parallel as possible. For outdoor, use silicone-insulated fine-stranded copper wire. For indoors, use thin (26 awg) PTFE/FEP insulated wires (thicker wires bulge the carpet causing havoc among 1/12 pancars). Silicone, teflon an FEP insulations last a long time. Avoid enamel-coated transformator-wires.
  • The termination resistor is important, anything between 330-470 ohms work. No soldering is strictly required: just weave the resistor's leads into the wire (under the insulation, between the strands), and wrap around strongly with ductape. No judgement 😄
  • The balun converts the parallel wire transmission line into a coaxial one. The linked balun can not accept wider wires than ⌀1 mm (20 AWG).
  • RG316 is an inexpensive, outdoor-proof, 50-ohm coax cable. Order with SMA male on both ends. Note, the male connector has the center protruding pin (as opposed to female connector, which has a socket to accept the pin) -- do not get confused by the threading of the connector.
  • The RTL-SDR is a bulky beast, won't fit directly into your laptop. Get an extension cable.

Software ​

Before running anything, install RTL-SDR driver with Zadig.

For debugging, you can test your setup with SDRAngel, as described at track setup tutorial

Using OpenStint is this easy:

  1. Download the Windows distibution from the releases.
  2. You can double-click on openstint_rtlsdr.exe to start with default parameters, or right-click -> edit start.bat to fine-tune parameters.

Lap counting and scoring ​

I develop LapBeeps, it support OpenStint natively.

There is a bridge for ZRound and RCGTiming, translating OpenStint's protocol to their native ones. These are packaged with the project in its .zip file.