Receiving systemWe are currently using iMet-1-ABxn 403 MHz radiosondes. These report temperature, humidity, pressure, and GPS position. They cost roughly $200 per unit, so we limit our launches to once or twice per year for teaching purposes.
The ground station is the highly portable iMet-3150 , which is essentially an off-the-shelf IC-R20 multi-band receiver together with an audio->modem->USB signal chain. The receiver must be configured with these settings to operate correctly with the newer 6 kHz bandwidth radiosondes.
The receiver provides an audio signal which is decoded by the modem and passed to a virtual COM3 port by way of the USB port on a Windows laptop. Alternatively, the audio signal can be plugged directly into the 1/8″ audio port on the laptop and decoded directly by software with that capability (e.g. Sky Sonde).
The standard software provided with the iMet-3150 system is iMetOS II.
From the vendor: “To download the software, you need to register at http://intermetsystems.com/ to get access to the Customer Resources tab. This is a simple process which also gives access to manuals and
other helpful documents.”
Here is a set of tutorial videos for an older version of the software. Part 3 is important! :
- iMetOS software installation
- Driver installation
- Disabling serial mouse detection
- Part 4?
- Setup of receiver and sonde
- Radiosonde flight
For the latter reason in particular, it is recommended that you use the record function of the IC-R20 receiver to capture the raw audio signal. You can subsequently play the audio back through the modem to capture the sounding in software, and if the software fails, you can repeat playback until the software is debugged.
The IC-R20 has three recording quality settings. “Fine” is only good for one hour. “Normal” is good for two hours and is probably sufficient both in quality and length, though I haven’t tried it yet.
SkySonde Client/Server software provides a lower-level interface to the balloon telemetry and allows additional flexibility. Here is the SkySonde user manual. It too requires Windows.