APRS Receiver Champion / Challenger Experiment

What’s a better receiver for an APRS receiver for packets from the ISS? Let’s do a side by side test.

Left is the challenger Baofeng, Right is the RTL-SDR Champion

For several months now, I have been running signals from a discone antenna on my roof into a RTL/SDR receiver connected to a Raspberry Pi. On a good day, I pick up a few packets from the ARISS digipeater running on the ISS at 145.825 MHz.

I was wondering if I could hear more packets with a different receiver so I decided to create a side/-by-side A/B test. Here’s the configuration:

Discone Antenna fed into my “Tech Center” / Ham Shack
Split antenna with a coax “T” – one goes to champion setup, one to challenger. Using equal length coax with SMA connectors.

Champion Setup: $30 RTL/SDR dongle direct into a Raspberry Pi 4 B (8 GB) running Raspbian with the Direwolf software.

Challenger Setup: Baofeng UV5R ($20) connected via audio cable to a UGreen USB audio jack ($14) into a Raspberry Pi 4 B (8 GB) running Raspbian with the Direwolf software.

Both are tuned as best I can for audio quality using data on 144.390, and then switched to the ISS frequency.

The experiment was configured on Wednesday, December 21 in anticipation of a predicted 83 Degree Elevation pass on 22-Dec-22 at 17:26 UTC. I’ll update this blog as I get pass data in.

Update: 23-Dec-22 at 0955 UTC – A moderate height ISS pass (32 deg El) coming through this morning at 1007 UTC. Couldn’t gather data Wednesday because the ISS radios were off for the space walk.

Update: 23-Dec-22 at 1023 UTC – ISS radios were still off during the pass. Trying again later today (Friday).

Challenger radio on left, champion SDR on the right.

Update: 23-Dec-22 at 17:00 UTC – Good pass with many packets caught. There was an obvious winner in the SDR. You can see on the screen show it captured many packets while the Baofeng only reported 1 for the entire pass. Going to change HT’s and try again on a later pass.