This blog article revisits the Vanguard 260 PL, a weather satellite receiver from the seventies that I found (as a rare bargain) on Ebay. It covers the 137 MHz NOAA low earth orbit (LEO) APT (image) weather satellite frequencies, when it’s fixed up with the correct crystals. I love the simplicity of the unit, and it reportedly works well given both the time period of the technology, and the low parts count.
The Cirrus adapter worked just fine on the Pi2, as can be seen in figure 1.0. I took the audio first from the “phones” jack of an old amateur radio receiver, and then from the sound card of a second PC running a browser webSDR page. This audio was connected via the “line-in” connector of the Cirrus adapter in the Pi2 box. In both cases the audio was very good, and was adequate to decode signals while using a only a moderate input level. The noise and spur levels were much less than on an i386 PC based machine I had used for FLDigi/ham activities in the past.
Figure 1: Status and printDetail() screen of the pingpair_dyn sample app (click to enlarge).
Finally, the unlicensed band nRF24 devices are talking to each other! It was a bit of a road trip. One thing to note is the importance of the status byte, and the other status data. While a hex 0x0e is normal, a hex 0x00 in the status byte, and/or lots of zeros in the printDetail() output are pretty good indicators that your SPI is not operational, and you’re not talking to the transceiver. More on this issue follows …