- Turnstile antenna (or arrow)
- USRP with TVRX
- WXAPT example from GNU Radio
This experiment is trivial, nonetheless it validates the RF-part of the setup. It will also reveal whether additional hardware like LNA is required.
Currently, following NOAA satellites are active on 137 MHz APT and 1.7 GHz HRPT:
|SAT||APT Freq||HRPT Freq||Notes|
|NOAA-15||137.5000 MHz||1702.5 MHz||VTX-1 / STX-2 / MSB / OMNI=RCP|
|NOAA-16||OFF||1702.5 MHz||— / STX-2 / MSB / LCP|
|NOAA-17||137.6200 MHz||1698.0 MHz||VTX-2 / STX-1 / LSB / RCP|
|NOAA-18||137.1000 MHz||1707.0 MHz||VTX-1 / STX-3 / HSB / RCP|
|NOAA-19||137.9125 MHz||1698.0 MHz||VTX-2 / STX-1 / LSB / RCP|
Considering a time window of 24h starting at 10:00 UTC on Sat 13 June, there are many potentially useful passes.
We only need a few good passes for successful experiment and they should be distributed over time in order to allow debugging and problem fixing between the passes.
- Created this page preparing for the experiment to be carried out during the weekend 13-14 Jun 2009.
- Need to upgrade laptops and install recent GNU Radio
- Upgraded laptops to Ubuntu 9.04 and GNU Radio 3.2
- Problems with example APT receiver since it uses 32k audio but my crap HW can only do 44k1 or 48k.
- I realized that I brought a BNC male/male adapter instead of a female/female that I need to connect my antenna to the TVRX. Experiment postponed!
- Tested GNU Radio with new OSS drivers from 4Front Technologies. Now I can use practically all sample rates not only 44.1kHz and 48kHz. See Sound Card Compatibility.
- Found out that there are resampler blocks in GNU Radio - very efficient ones indeed!
- blks2.rational_resampler_* for Python
- gr_rational_resampler_base_* in C++ (see under filters)
- GRC has both blocks? Have to find out about it.
- Followed a NOAA-17 pass (max el 18°) using USRP+TVRX+Arrow. Very good SNR between 20-30 dB.
Received NOAA-15 using turnstile, USRP+TVRX. Good signal but lost quickly. The antenna is definitely worse than the arrow.
- Do not pack your gear in a hurry.
- RTFM (RE: resampling audio) — also the examples!