Tonight I had some fun with Fldigi connected to Web SDR. I could actually listen to and decode digital ham radio traffic on the 80 and 40 meter bands without using a radio or antenna.
The way I achieved it was by configuring Fldigi to capture its data using the built-in microphone and turn the volume in Web SDR up until it was sufficient. The result was surprisingly good; of course partly because the Mac has relatively good sound hardware – at least when compared to some standard PC sound chip.
I prepared this video demonstrating how it works. You will hear and see many PSK-31 stations as well as some RTTY and other modes. Enjoy and have fun.
I made good progress with the portable S-band ground station this week.
I took the receiver to the OZ7SAT lab to measure its performance. Using the USRP+DBSRX and no LNA we could easily detect a -132 dBm CW signal with modest FFT integration (fraction of a second) in a GNU Radio spectrum scope. Using the LNA we could go down to about -138 dBm, i.e. an improvement in SNR of 6 dB. These figures were measured at an SNR ~5 dB. This is excellent, but please note that this is not real “sensitivity” in the traditional sense because we were not demodulating or decoding the signal. We were simply integrating the spectrum for a fraction of a second to detect the presence of the signal. The measurements were done by sampling a 250 kHz wide spectrum.
In this new video blog I am introducing a new project that has kept me occupied for a few weeks now: A low cost S-band ground station for receiving signals from NASA’s lunar spacecrafts LRO and LCROSS. More info at Receiving LRO and LCROSS. Based on the Universal Software Radio Peripheral (USRP) with DBSRX daughterboard, a super low noise preamplifier from Kuhne and GNU Radio software.
I heard about the Arrow II Satellite antenna quite some time ago and even seen a lots of videos about it on YouTube. Unfortunately, whenever I look for an opportunity to get one, I couldn’t find it anywhere in Europe. Until recently, when I learned by a coincidence that Antenna Warehouse is also shipping them to Europe! Didn’t have to think long before I decided that I can’t live without one and so I ordered one on July 21st, 2009.
The price I had to pay was a bit of an issue. Although the antenna costs $139, which I find very acceptable, the shipping and import costs from US to Denmark are usually a very traumatic experience. This time I only had to pay $39 for the shipping, which is fine, but then came the EU import duty and Danish VAT, which was an additional $70.
So was it worth the price? Well, let me see:
It took two and a half weeks for the antenna to arrive but this included one week delivery to Antenna Warehouse — they did not have it on stock just when I ordered. I find this delivery time acceptable given the circumstances.
Once I had the antenna in my hand, it took me less than 5 minutes to assemble it without looking at the instructions.
Shortly after the antenna was assembled for the first time I had a good VO-52 pass where I heard many EU stations up to S8 on my FT-817.
Before the pass was over FO-29 came within range in a very low pass (maximum elevation below 5 deg). Nonetheless I heard K3SZH working EU stations. Wow!
Later that day I had a good AO-27 pass with strong signals. I heard many voice contacts in the beginning of the pass until some packet came on and killed them all (don’t know if it was telemetry (see the video below).
The overall construction of the antenna looks very good. I would certainly place it in the high quality end of the scale. I was also happy about the packaging; The boom, the 2m elements and the 70cm elements were in three separate plastic bags.
Each element has a red end cap on each end that makes the antenna look good 🙂
So, yes, all in all I am very impressed with the Arrow antenna so far. Next step is to set up my FT-817 to transmit and try to have some contacts. More on that later!
On July 20, AMSAT will mark the 40th anniversary of the first manned lunar landing with a special event on the AO-51 amateur radio satellite. During evening passes in the U.S. and Europe, AO-51 will transmit a message commemorating the event. The message will be transmitted on the 435.300 MHz FM downlink and will contain a Robot 36 SSTV image as well as a voice message. It is often possible to receive AO-51 with a simple NFM capable receiver + rubber-ducky antenna and you can use this online prediction tool to find out when AO-51 passes will occur at your location.