WSPR Results with Two Different Sound Cards
February 24, 2011 Leave a comment
I’ve been running WSPR non-stop for the past 3 weeks remotely on a Giada N3 computer connected to a Softrock Ensemble II RX. In the middle of the period, I switched from the Giada’s internal sound card to a 24-bit external USB sound card. WSPR was hopping the entire period between the 7, 10, and 14MHz bands. The antenna used was my wideband active loop.
To compare the two cards, I compared the log files two consecutive 1-week periods, one with the internal sound card and the other with the external card. The periods were February 7 to 14 and February 14 to 21.
The results suggest that the external card delivers better results, but not by a huge margin. The internal card collected 3148 spots in a week; the external card collected 3825. The vast majority of the spots are of European stations. The other spots include 89 from the US and 20 from Australia with the internal card, versus 117 and 38 with the external card.
The results are not completely scientific. Activity of transmitting stations might have been a bit different in the two weeks, and the level of interference might have been different (some major contests sometimes cause interference to WSPR, but I don’t think any took place during these two weeks). The weather might have played some role too, because the Si570 synthesizer drifts a bit with temperature, which can causes WSPR to search for signals at the wrong frequency if it’s very warm or very cold. Temperatures here have not been extreme enough to move WSPR completely off-band, but perhaps I lost some spots near the band edges. (I tried to run frequency calibration every half an hours or so, but the scheduling code does not work reliably yet.)
Still, I think that it’s safe to draw two qualitative conclusions: (1) the built-in internal card on the Giada N3 is not as good as a high-quality sound card, but (2) it’s quite usable nonetheless for WSPR and similar digital modes.
I was very happy to see the outdoor setup work non-stop for 3 weeks. Things did get quite hot at times, but it kept working. This morning it crashed around 10:30am. I am not sure why; maybe it overheated. I turned it back on and it’s working fine again. But I don’t think I’ll be able to leave the computer outside in the summer; it will get too hot. I’ll have to find an indoors place for the computer and radio.
Now that this experiment is over, I modified the remote setup slightly. A added a passive antenna splitter and a crystal-controlled 7MHz Softrock Lite II receiver. This receiver monitors the 7MHz band continuously, and the Ensemble II RX is hopping between the 3.5, 10, 14, 21, and 28MHz bands, running two copies of WSPR concurrently. Since this morning, I already collected spots on all of these bands, and from both receivers.