The Realtek 2832U

In my spare time (lol!) I have been fooling around with one of those RTL 2832U dongles and a bit of software.  For those that don’t know, the RTL 2832U is a COFDM demodulator chip designed to work with a USB dongle.  When coupled with an R 820T tuner a broadband RF receiver is created  There are many very inexpensive versions of these devices available on Amazon, eBay, and other such places. The beauty of these things is that for around $12-30 and a bit of free software, one can have a very versatile 10 KHz to 1.7 GHz receiver.  There are several good software packages for Windoze, Linux, and OSX.

The one I recommend for beginners is called SDR-Sharp or SDR#.  It has a very easy learning curve and there is a lot of documentation available online.  There are also several worthwhile plugins for scanning, trunking, decoding, etc.  At a minimum, the SDR software should have a spectrum analyzer, waterfall display, and the ability to record audio and baseband PCM from the IF stage of the radio.

Some fun things to do; look at the output of my reverse registering smart (electric) meter (or my neighbor’s meter), ACARS data for the various aircraft flying overhead, a few trips through the EZPass toll lanes, some poking around on the VHF hi-band, etc.  I also began to think of Broadcast Engineering applications and a surprising number of things came to mind:

  • Using the scanner to look for open 950 MHz STL frequencies
  • Inexpensive portable FM receiver with RDS output for radio stations
  • Inexpensive Radio Direction Finder with a directional antenna
  • Inexpensive Satellite Aiming tool

Using SDR sharp and a NooElec NESDR Mini+ dongle, I made several scans of the 945-952 STL band in a few of our markets.  Using the scanner and frequency search plugin, the SDR software very quickly identified all of the in-use frequencies.  One can also look at the frequency span in the spectrum analyzer, but this takes a lot of processing power.  The scanner plugin makes this easier and can be automated.

950 MHz STL frequencies, Albany, NY
Analog and digital 950 MHz STL frequencies, Albany, NY

I also listened to the analog STLs in FM Wideband mode.  Several stations are injecting their RDS data at the studio.  There is one that appears to be -1500 Hz off frequency.  I’ll let them know.

Next, I have found it beneficial just to keep the dongle and a small antenna in my laptop bag.  Setting up a new RDS subcarrier; with the dongle and SDR# one can quickly and easily check for errors.  Tracking down one of those nasty pirates; a laptop with a directional antenna will make quick work.

Something that I found interesting is the waterfall display for the PPM-encoded stations:

WPDH using RTL 2832U and SDR Sharp
WPDH using RTL 2832U and SDR Sharp

Not only can you see the watermarking on the main channel, you can also see the HD Radio carriers +/- 200 KHz from the carrier frequency.  That is pretty much twice the bandwidth allotment for an FM station.

WDPA using RTL 2831U with SDR Sharp
WDPA using RTL 2831U and  SDR Sharp

Those two stations are simulcasting.  WPDA is not using Nielson PPM nor HD Radio technology.  There is all sorts of interesting information that can be gleaned from one of these units.

Aiming a satellite dish at AMC-8 can be a bit challenging.  That part of the sky is pretty crowded, as it turns out.  Dish pointer is a good general reference ( and the Dish Align app for iOS works well.  But for peaking a dish, the RTL 2832 dongle makes it easy to find the correct satellite and optimize the transponder polarization.  Each satellite has Horizontal and Vertical beacons.  These vary slightly in frequency, thus, but by tuning to the correct beacon frequency, you can be assured that you are on the right satellite.  All of the radio network programming on AMC-8 is on vertically polarized transponders, therefore,  the vertical beacons are of interest.  Here are the vertical beacons for satellites in that part of the sky:

Satellite Position C band Vertical beacon (MHz) L band (LNB) Vertical beacon (MHz) Comment
AMC-8 139W 4199.5 949.25
AMC-7 137W 3700.5 1450.25
GOES15 135.4W 2209.086 N/A NOAA WX
AMC-10 135W 4199.5 949.25
Galaxy 15 133W 4198 949.00
AMC-11 131W 4199.5 949.25
Galaxy 12 129W 3700.5 1450.25

For those in the continental United States, there is not much else past 139W, so AMC-8 will be the westernmost satellite your dish can see.  Of course, this can be used in other parts of the world as well, with the correct information. Bringing a laptop or Windows tablet to the satellite dish might be easier than trying to drag a XDS satellite receiver out.

AMC8 vertical beacon output from LNB
AMC8 vertical beacon output from LNB

In order to use the RTL-2832U, simply split the output of a powered LNB, and install a 20-30 dB pad in between the splitter and the dongle.  Using the vertical beacon on 949.25 MHz, adjust for maximum signal.

For some other uses; look for the nearest and best NOAA Weather radio station.  Several times the local NOAA weather station has been off the air for an extended period of time.  Sometimes, another station can be found in the same forecast area.  Heck, couple these things to a Raspberry Pi or Beaglebone black, and a really nifty EAS receiver is created for NOAA and broadcast FM.  One that perhaps, can issue an alarm if the RSL drops below a certain threshold.

I am sure there are plenty of other uses that I am not thinking of right now…

The efficacy of the computer generated voice

I was just listening to the latest broadcast of severe thunderstorm and tornado warnings rolling in across WXL-37 for upstate NY:

Trouble is a brewing
Trouble is a brewing

It looks a little bit hairy to the north.  There is a lot of rumbling around to the west of us and we are prepared to head for the basement in event of a tornado in this area.

At some point in time, somebody decided that computer-generated voices were exactly right for emergency communications. Never mind some of the quirks that can be encountered.  These are mostly pronunciation errors for places like Saugerties, normally spoken as Saw-ger-tees but the NOAA computer voice says S-ouw-jer-tees.  That is understood well enough, but frankly, there are other place names that go by so fast that I cannot make sense of what the computer is saying.

Another good example of this is the Coast Guard’s computer voice confusion around the word “November.”  In the military (NATO) phonetic alphabet, November is the word used to express the letter N.  For some reason, the word itself seems to be a bit of a mystery to the computer, which sometimes renders the word November as “NOVEMBER OSCAR VICTOR ECHO MIKE BRAVO ECHO ROMEO.”  For those of us who have been in the military, this makes perfect sense.  Why just say “November” when you can say much more, waste time, and confuse the un-aware?  This particular computer voice is nick-named “Iron Mike.”

Computer-generated voices can be hit or miss.

Then there is the computer voice from Shannon VOLMET:

Even on HF Single Side Band, that voice is clearly more understandable than the NOAA voices in use today. The issue is, many broadcast stations now use the NOAA computer voice to broadcast weather alerts to their listeners.  If I were driving in my car with lots of background noise, I likely would not get most of the information being relayed by the broadcast station via EAS.  I suppose gone are the days of a professional broadcaster’s voice clearly imparting information and comforting the listeners during times of calamity.  Sigh.

Upgrading National Weather Service Radio transmitter

If you have ever wondered about those ubiquitous NOAA all hazards radio (formerly National Weather Service radio) stations, wonder no more. These stations transmit on one of five frequencies in the 162 MHz band with power ranges between 250 and 1,000 watts.  There are over 1,000 transmitters scattered throughout the country including outlying territories like American Samoa, Guam, Northern Marianas, Virgin Islands, and Puerto Rico.

The original 1958 plan was for these stations to transmit Aviation and Marine weather forecasts.  The system was expanded for use by the general public in the early sixties.  Since that time, it has been slowly expanding, with the most recent survey concluding that NOAA weather radio station can be received by 95% of the US population.

One of those stations in my neck of the woods is due for a transmitter upgrade. WXL-37 uses two Scientific Radio Systems SR-416P  transmitters, as a main and a standby.  The programming audio comes from the NWS office in Albany, New York, via TELCO line.  The old transmitters are tube type made by in 1976.   They are reliable transmitters, however, after 34 years of continuous use, they are getting a little tired.  They are also big and bulky and since Scientific Radio Systems went out of business, not been supported.

This year, NOAA is replacing these transmitters with a Nautel NG1000.  I have worked with Nautel’s military-grade transmitters before and found them to be extremely rugged.  Those transmitters are what the original AMPFET design was based on.  Nautel is not the only vendor that NOAA is using however, others include Armstrong Transmitters and Crown Broadcast.

Scientific Radio System SR416P transmitters
NOAA Scientific Radio Systems SR416P VHF transmitters

The Nautel NG1000 is a little thing, taking up about half an equipment rack with an outboard cavity filter and dummy load.  There are two drawers, a controller an antenna switch, and a remote control.  Each drawer is its own 1 KW transmitter.  The GUI is on a laptop, which is what I prefer.  If there must be some sort of computer-driven GUI, then make it removable, so that when lightning strikes the 1,000-foot steel lightning rod 25 feet away, it doesn’t get blown up.  Each transmitter is connected to a 30 AMP 240 Volt breaker via a 4-prong twist lock plug.

Nautel NG1000 transmitter
Nautel NG1000 NOAA transmitter

The antenna for this station is near the middle of this 1,000-foot tower, thus the station gets excellent coverage with a TPO of 1,000 watts.

American Tower, Highland, NY
American Tower site, Highland, NY

On a related side note, the computer synthesized voices normally heard on NOAA stations took several years to evolve.  Remember when this began back in the mid 1990’s with “Paul.”  Several years later, “Craig” and “Donna” were introduced.  Finally, “Tom,” is able to change voice inflections for emphasis.  When I was in the Coast Guard, we did high seas synopsis and forecast on HF without aid of computers.  At times, especially during typhoon season, it got a little busy in the weather broadcast position.  There are advantages and disadvantages to both methods.  Personally, I’d rather hear a human voice, especially in a crisis.