After leaving my RTL-SDR for one year, last month, I had a chance to test it again. Yes, last month , World Cup 2014 began on June and ended on July. How World Cup was related to RTL-SDR testing? Due to the east and west time zone differences, local time for match schedule in my country (Myanmar) is beyond midnight. It was a chance to make, test something while waiting for the matches.
I remember an article about tracking hobby, educational satellites with rtl-sdr. Goggled and found out these articles, good to go.
Tracking NOAA Weather Satellite with RTL-SDR,
Then, checked when NOAA sats will passed my location from these satellite tracking websites.
Checked that active sats regularly pass my location before midnight. Great, that is how I my rtl-sdr was related to world cup :D.
I read article and follow instructions thoroughly. Installed required software,
- SDR# for receiving Sats
- VB-cable for audio piping from rtl-sdr to sound card
- Orbiton for tracking satellites
- WXtoImg for decoding the APT signal
Most of rtl dongles have more or less tuning freq error. After finished installation of all software, I calibrated freq ppm error with these instruction. It is sample, monitored local GSM freq band and adjusted error.
What I need was an external antenna for 137~145 MHz reception. I built Ground Plane antenna in an evening because this is easy to build.
Each antenna element = 51 cm, used old N type RG213 male connectors for assembly.
Finished and installed antenna.
After tuning and trials, I track and tuned NOAA-15 satellite signal successfully.
But the decoded image was noisy and not good.
2# Second Antenna (QHF)
After several attempts, I realized that a good antenna was required for better reception. So, I tried to build second DIY antenna. After a few research, I chose Quadrifilar Helix (QFH) antenna type.
Design calculation can be done here.
And here is ready made design by G0HPO.
First , collected required copper wire (12 gauge, enamel), female RG213 connectors, coax-cable , wood rod etc. Then, tried to bend, loop copper wire for helical shape.
Soldered feed point with the help of small PCB.
Loop the balun and connector.
Final assembly, also attached recycled rain drop covers for feed and connector :D
Hoisted the antenna, ready to go.
As expected, second attempt results ware not so bad. The receiver show more stronger signal than first antenna.
There are still noises in receptions when sat is at lower azimuth.
- QHF antenna is better reception than Ground plane
- BUT, QHF is a lot noisy than Ground plane
- Do I need parabolic or YaGi with tracking ?? for next
# Final thought
Sure, I need LNA for next and future test. Need to find out the list for DIYable LNA.
Fun midnight modern hamming while waiting for World Cup.