RF Shorts for Nov. 7, 2014

LS Telcom Analyst Disputes ITU Spectrum Predictions
Caleb Henry reports “IMT operators are not using all the spectrum already available, according to LS Telcom” in his SatelliteToday.com article LS Telcom Analyst Disputes ITU Spectrum Predictions. He continues, “A top concern of the satellite industry is that C band might be given to terrestrial mobile and wireless operators. LS Telcom Director of Spectrum Consulting Richard Womersley worries that the data the ITU is currently using to guide spectrum decisions is not as reliable as it should be.”

The article has this quote from Womersley, “If you look at the forecasts that were produced for 2015 by the ITU, and compare that to spectrum that’s even feasible to be licensed, as well as what is licensed, there is a massive gulf. Those forecasts that were produced in 2007 are clearly way off. Not only has [the IMT community] not proven the need, but even with that which is available, they haven’t got all of it in use. Until you have all that in use I don’t see how you can really push for more.”

For more details, see the LS Telcom report Analysis of the World-Wide Licensing and Usage of IMT Spectrum. Figure 4-3 shows that in the United States, 400 MHz of spectrum is potentially available that isn't currently licensed.

Using an RTL-SDR to Receive Dead Satellites

When using an RTL-SDR to download live satellite images from the 137 MHz NOAA polar orbiting satellites I've been surprised at the number of other signals in this band. Their characteristics indicate they are satellites and I've been able to identify some as Orbcomm satellites or military satellites. It turns out some of the unidentified signals might be from old decommissioned satellites.

Website RTL-SDR.com has a posting discussing Receiving Dead Satellites with the RTL-SDR. Happysat, a reader of RTL-SDR.com writes: “During weathersat reception of NOAA/Meteor on the 137 MHz band I did see quite often unidentified interrupting signals. After a bit of Googling around I learned that these were Dead Satellites that still are broadcasting given the right sunlight conditions, the signal strength is sufficient to show up in SDRSharp, not all signals are very strong some very weak and needed a good close up zoom in SDRSharp. There are many shutdown satellites who apparently having a life of their own varying from Military, Navigation, Experimental, Weather, and also Amateur ones.”

If you have an RTL-SDR and a decent outdoor antenna, the RTL-SDR article provides some tips on what dead satellites look like on an SDR's waterfall display and provides links to TLE data for anyone who wants to track them. Additional sites of interest include Mike Kenny's web site with a list of frequencies and a collection of images and original sounds from DD1US.

Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.