Our WebSDR Installation

Access via web browser to http://44.62.14.18:8901/
Note:  The site was not working the last I checked. (4/11/2024 @ 7:15 PM MST  Please, Let the webmaster know if you find otherwise

List of worldwide webSDRs at http://websdr.org

Some time ago folks were unhappy that many of the Green Valley stations were difficult to copy on the various 20 meter nets. Casey, KF7RCS, took the initiative to build a webSDR and install it at his residence. It indeed worked well, but it seemed likely it would work better if placed at our Elephant Head site.

This is a picture of a similar webSDR setup.

The small package labeled rtlSDR to USB Hub is one half of a state of the art receiver. The output is fed to the other half, an Arduino computer, where the SDR output is massaged into what the user wants to hear. The USB Hub shown connected to the rtlSDR unit is there only to provide power to the unit that the Arduino is not able to do. The remaining white box is a router in which Casey can make the output of the WebSDR available to users on the internet. Ignore the IP address shown on the Arduino, access is via
 http://44.62.11.162:8901  

Ultimately the equipment was located in a data cabinet that also houses the 145.29 analog and the 449.375 DMR repeaters.

This picture shows Ron, AA7RP working on equipment.

The photographer didn’t notice the wires in Ron’s face when the picture was taken, but that’s the way it really is in that box.

Of course, it is a radio and radios require antennas. Location is one of the key ingredients and in this picture we can see how this site actually overlooks Elephant Head in the foreground and shows Green Valley and Sahuarita in the distance. Ed, N9MW, set about building a vertical antenna that could withstand the weather elements on the ridge. Dave, K2SS, contributed heavy duty aluminum for the vertical section. A vertical is appropriate as most local line-of-sight users are limited to “flagpole” type antennas. A dipole would be cross polarized to most local signals and would cost about 30db attenuation.

This picture shows the three foot galvanized steel mounting stub coupled to the 1.25 inch radiator section with eight layers of fiberglass cloth. Antenna feed line and radial connections are shown.

Custom brackets (metal supplied by Beetle, K7GSB) and radials were also needed.

Here's Casey atop the 40 foot tower  after the antenna was mounted and now is on his way down the tower securing the feed line to a tower leg.

 

Performance met and exceeded our expectations. Well, not really, we were all very confident this thing was going to play very well. But, it’s not perfect.

We can adjust the radial lengths to improve the SWR since it is a raised radial design, but tweaking the system will probably not improve performance very much as users presently report excellent reception to and from the system. 

The elevation pattern seems ideal for the purpose.  The graphs display an EZNEC analysis of the antenna.

The following is a screen shot of the webSDR in action.  Log in and try it for yourself.

Ed Toal, N9MW 1-25-22