West Coast Evening

Time for some radio and physical exercise again!

Emphasis for this run was to assess whether the Raspberry Pi 3B+/RSP1a SDR/Cubic SDR/WSJT-X system, which does away with the need for a conventional 12V-powered rig as receiver, works properly.

Three WSPR RX systems running at 14MHz last evening:

(1) Home: FT450, HP laptop, WSJT-X, vertical delta loop

(2) Home: TS480-SAT, Raspberry Pi 4B, WSJT-X, elevated 1/4 wave vertical, 2 elevated radials

(3) Beach (west-facing coast) RSP1A SDR, Raspberry Pi 3B+, WSJT-X (via Cubic SDR), identical 1/4 wave vertical to home.

WSJT-X in all cases was the latest available version.

IO73RF WSPR listening.

I ran WSPR for 50 minutes (19:14-20:04UT) at the beach, during which time the received signals at any given antenna were broadly stable.

The difference between the vertical at the beach and the vertical at home was a median +8.25dB in favour of the beach, with a range of +3dB to +12dB, based on an analysis of ten randomly-selected stations heard.  This result is entirely consistent with previous findings during the late afternoon/evening period from the west coast.

Still a bit of a mess, but at least it all runs off a USB 5V battery, is lightweight, and fits in a backpack!

The Raspberry Pi/SDR backpack system, which makes a reasonably high demand on the Pi's processor, does not therefore appear to suffer from any problems and can be considered a reliable receiver.  Note that you do need to have RF sampling at its lowest setting of about 250kHz, and audio sampling down at 16kHz or even 8kHz.  This is perfectly fine for HF.

The difference between the home delta and home 1/4 wave vertical was a median +5dB in favour of the delta loop, range of -2 to +19.5dB.

So, an elevated vertical at the beach is outperforming an inland full wave vertical delta loop (essentially, a pair of close spaced verticals), by 3dB on average, remembering and accounting for the fact that the 1/4 wave vertical has ~5dB less inherent gain than the delta.

Nearly time to go home.

Of course, on certain paths, and certain times of day, the beach location makes a very much larger difference.  Also, the signal from OX3HI was heard at -28.5dB median signal at the beach, but was not heard at all by either of the home antennas.