GRAPT/RF Validation
From MyLabWiki
- 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.
Contents |
Frequencies
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 |
Source: NOAASIS Satellite Status Information
TODO: METEOR, MetOp and NPOESS?
Passes
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.
2009-06-11
- 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
2009-06-12
- 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.
2009-06-13
- 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!
2009-07-04
- 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.
2009-07-10
- 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.
2009-09-16
- Followed a NOAA-17 pass (max el 18°) using USRP+TVRX+Arrow. Very good SNR between 20-30 dB.
2009-10-10
Received NOAA-15 using turnstile, USRP+TVRX. Good signal but lost quickly. The antenna is definitely worse than the arrow.
Lessons Learned
- Do not pack your gear in a hurry.
- RTFM (RE: resampling audio) — also the examples!
