An Antenna Splitter and Two Receive Chains
January 1, 2011 2 Comments
Once I figured out how to use my crystal-controlled Softrock under WSPR, it seemed a shame to use only one receiver at a time. I should be able to use the 7MHz Softrock to monitor that band and the Softrock Ensemble II RX to monitor the other bands.
The easy part turned out to be feeding the two receivers. I built an antenna splitter designed by Dave Johnson and published on Todd Gale’s web site. It’s a simple device with two toroid transformers and one resistor. I didn’t measure it’s performance, but it works.
The audio from the two Softrock receivers is routed to two separate USB sound cards. I tried to connect both of them to my laptop, running Windows XP. Only one sound card was usable; the other did not show up on the audio menus and it shows up as not working in the Device Manager. I guess that the Creative device driver for the card can only cope with one card being connected to the PC.
I then tried to connect at least one of the cards to Linux running under VirtualBox on the same laptop. Linux saw the card but WSPR failed when trying to read audio from it.
I gave up and connected the two cards to two different computers. This obviously worked fine. I ran the setup all night. The 7MHz receiver generated more than 900 spots (more than usual, which is around 500; could be better proparation or more people transmitting). The Ensemble II RX was initially hopping between 5MHz and 10MHz. This generated my first-ever 5MHz spot, of a station in the UK. After a couple of hours I switched it to hop between 3.5MHz and 10Mhz. This generated two dozen spots at 3.5MHz (including my first 3.5MHz spot of a station in the US, more than 11,000km away) and more than 140 spots at 10Mhz.
I still need to figure out how to do this with only one computer.