Tuesday, December 23, 2008

XML 1.1 Web service deprecation notice

The existing REST based RadioReference.com web service (XML 1.1) will be formally deprecated on April 1st, 2009. The script will be removed from service at midnight on that date.

I encourage all developers of applications that are using this interface to to migrate support to the new SOAP based Web service, documented at:


The WSDL for the SOAP based Web service is at:


We are deprecating the REST based Web service because it makes no sense for us to duplicate maintenance and new feature releases across multiple Web service types.

Thursday, October 30, 2008

VHF/UHF Spectrum Analysis using the RF Space SDR-14

One of the most impressive developments in the radio communications community over the past few years is the advent of software defined receivers, which can provide great tools for spectrum analysis. Hobbyists today can not only view entire swaths of spectrum at one time to view activity, but can also record entire spectrum chunks for later playback and analysis using SDR tools.

This article will walk through the RF Space SDR-14 software defined receiver, and review how it can be used to analyze different user segments in the VHF/UHF spectrum.

To start, an introduction is in order. The RF Space SDR-14 is a 14-bit software defined radio receiver that operates in the 0.5-30 MHz band. It provides not only extensive spectrum analysis capabilities but also functions as a great receiver with numerous demodulation capabilities for the HF spectrum. Since the SDR-14 is a software defined radio, all controls and interfaces with the radio is done using software applications installed on a PC. The most popular application written to exploit the SDR-14 is SpectraVue.

As mentioned above, the SDR-14 functions as an HF software defined receiver, however it can be configured to accept the 10.7 MHz IF output from another receiver, and tune that receiver, to combine as a very powerful monitoring station and spectrum analysis platform for any band range. I have been using an AOR5000A in conjunction with the RF Space SDR-14 with excellent results, allowing me to click on certain portions of the spectrum and automatically tune the AOR receiver.

Showing some of the capabilities of this combination or AOR receiver and RF Space spectrum analysis tools, I'll review some annotated screen shots of different monitoring targets. You can click each screenshot to view the full size image.

The first we will review below is a screenshot of the SpectraVue application monitoring a 250 KHz wide chunk of spectrum between 260.350 and 260.600 MHz - where US Military UHF communications satellites have downlinks. The RF Space can realistically monitor about 10 MHz of spectrum from another radio's IF, however the narrow swath of 250 KHz allows us to monitor military satcom transponders transponders and see what is happening within each of them.

In this screenshot, we can see the 4 Active UHF SATCOM transponders:

1. Relaying unknown data bursts on 260.375
2. Relaying a Spanish bootlegger's communications on the 260.425 transponder but comms centered on 260.430 MHz. The transponder is 25 KHz wide so the communications come through loud and clear.
3. Relaying 16 KHz VINSON encrypted US Military voice
4. Relaying a Spanish bootlegger's communications on the 260.525 transponder but comms centered on 260.530 MHz.

It is interesting to note that Spanish, Portuguese, and Asian bootleggers at times use all the 25 KHz wide transponders, with communications in LSB, AM, and FM.
Next, let's take a look at the 5 KHz transponders on the Gapfiller Military SATCOM satellites. This screenshot shows (13) 5 KHz wide transponder in action, annotated with different traffic occurring on those. You can clearly see in the screenshot weaker active transponders for a different satellite on the left, and the 13 stronger transponders for the target satellite.

Now that we have reviewed some advanced monitoring targets, we can take a look at some more common monitoring targets that hobbyists focus on. Below is a screenshot of a 10 MHz wide section of spectrum in the VHF aircraft band. This shows a key benefit of using the SDR for spectrum analysis -- you can watch almost the entire VHF aircraft band on one screen, and click to tune a specific transmission on the AR5000 radio.

Further, why search the federal government VHF land mobile spectrum on a standard scanner when you can watch the entire band in one window? Below is a screenshot of the SDR monitoring 162-172 MHz, providing the ability to see all activity and click to tune the AOR radio to specific transmissions:

And finally, where I live, the federal UHF band in San Antonio TX is quite busy with a large wide area military trunking system active between 406-411 MHz. The screen capture shows activity over time in that spectrum, showing active data and voice channels.

In summary, you can see that the RF Space SDR-14 opens up a whole realm of possibilities for radio communications enthusiasts. The ability to watch entire blocks of spectrum and then point and click to tune an transmission makes finding new and unknown monitoring targets a breeze.

For those that are interested in adding this fine piece of communications equipment to their shack, Scanner Master offers the RF Space SDR-14 for sale on their fantastic Web site. Click the link below for more details on how to order.

RF Space SDR-14 on Scanner Master

Next up, we'll review the RF Space SDR-14 monitoring the HF bands. Utility, broadcast, and Ham listeners and operators will get a whole new perspective on how HF Spectrum is used.

Monday, September 22, 2008

RadioReference.com and Scanner Master Corp. Renew and Extend their Partnership

RadioReference.com, the Web's premier resource for radio communications information, and Scanner Master, the nation's oldest and largest Scanner-only dealer, today announced the renewal and extension of their joint-marketing partnership.

Through this partnership, the most comprehensive line of scanners, software, antennas and communications-monitoring accessories, sourced from around the world, are offered to the world's largest online community of two-way radio users. RadioReference is also developing exciting new products services which will be marketed through Scanner Master starting later year.

Richard Barnett, president of Scanner Master Corp., remarked, "Our partnership with RadioReference.com is our most important. It allows us to present scanners and accessories to an enormous audience of dedicated radio professionals and hobbyists. Through this relationship, we strive to provide unmatched service and a wide product mix to the RadioReference.com audience through our strict focus on scanners and scanner users.

Lindsay Blanton, president of RadioReference.com LLC, said, "Scanner Master is widely recognized in the radio communications community as the leading provider of scanners and communications equipment to the industry. This, coupled with their leadership in innovating new products and offerings for the industry means that this partnership will continue to grow and be very successful."

With its extensive frequency and trunking databases, news sections and user forums, RadioReference.com is the one-stop repository of radio communication information.

For over 30 years Scanner Master has served the radio community through its line of popular Scanner Master and Monitor America books as well as through the sales and service of scanners, accessories, software, antennas and other custom products.

Tuesday, July 8, 2008

VHF Low Band Skip - Tips and Tricks to monitoring

Now that the summer months are upon us, VHF Low Band Skip reports have been coming in fast and furious on the RadioReference Skip Forum. This article will give you some tips and tricks on how to monitor public safety and military communications from all over North America with a simple antenna and scanner. The trick is timing, and patience.

VHF Low Band Skip is caused by a phenomenon called Sporadic E skip. Sporadic E skip occurs when patches in the E layer of the ionosphere, about 65 miles above ground, become ionized. This layer normally refracts shortwave and mediumwave signals but is transparent to VHF radiation. When patches of the E layer become ionized, great skip opportunities from 28 MHz to 75 MHz occur, allowing you to monitor communications in this band cross-country, and sometimes worldwide when "double-hop" skip occurs.

Hunting for skip.

One very valuable tool for looking for E skip patch openings is the DX Sherlock 1.7 - V-UHF QSO real time maps tool. This tool, provided by vhfdx.net, shows real time contacts made by amateur radio operators on 6 meters (50-54 MHz). Usually, when a number of contacts are being made cross country, a sporadic E skip opening is occurring.

Another valuable tool is of course your scanner. Some precursors to sporadic E skip come from meteor scatter transmitter sites which broadcast near 40 MHz for telemetry and weather reporting. Meteor scatter transmissions are similar in nature to sporadic E skip transmissions, except the radio communications broadcast bounces off on ionized trails from naturally occurring meteors vaporizing in the atmosphere. These vaporization trails allow ground stations to communicate over long distances from remote areas. Some frequencies commonly used by Meteor scatter systems include:

40.53 SNOTEL - Snowpack Telemetry in the Western States
44.20 Meteor Communications Corporation

Plug those frequencies in and scan them often. If you hear data (you'll know it when you do, it is a loud buzzsaw sounding data transmission) on these frequencies, chances are a nice band opening is occurring.

Common Reported Skip

Some of the more commonly public safety agencies that show up on skip across the nation include:

42.00 - 43.00 MHz Missouri Highway Patrol
42.00 - 43.00 MHz Tennessee Highway Patrol

33.90 Hamilton County (Cincinnati) Fire / EMS Dispatch

39.00 - 40.00 MHz California Highway Patrol

Some of the more commonly heard Military stations include:

30.45 Fort Hood Range Control
38.90 Fort Irvwin CA Range Control / Fort Knox TN Range Control

In addition to those public safety agencies and military operations, there are numerous other fire departments, police departments, SOs, pagers, Mexican taxi drivers, military range controls, military helo towers, public works, and other operations that occur.

The full set of low band allocations in the United States are:

30.0000 to 30.5500 U.S. MILITARY
30.5800 to 31.9800 PARK SERVICE
32.0000 to 33.0000 U.S. MILITARY

33.0200 to 33.1000 HIGHWAY SERVICE

33.1200 to 33.4000 BUSINESS RADIO

33.4200 to 33.9800 FIRE DEPARTMENTS

34.0000 to 35.0000 U.S. MILITARY

35.0200 to 35.6800 PAGERS

35.7000 to 35.9800 BUSINESS RADIO

36.0000 to 37.0000 U.S. MILITARY

37.0200 to 37.4200 POLICE

37.4400 to 37.8800 BUSINESS RADIO

37.9000 to 37.9800 HIGHWAY SERVICE
38.0000 to 39.0000 U.S. MILITARY

39.0200 to 39.9800 POLICE
40.0000 to 42.0000 U.S. MILITARY

42.0200 to 42.9400 POLICE

42.9600 to 43.1800 BUSINESS RADIO

43.2000 to 43.6800 PAGERS
43.7000 to 44.6000 BUSINESS RADIO

44.6200 to 46.0400 POLICE AND PARK SERVICE

46.0600 to 46.5800 FIRE DEPARTMENTS

46.6000 to 47.0000 U.S. MILITARY

47.0200 to 47.4000 HIGHWAY SERVICE

47.4200 to 47.6600 EMERGENCY SERVICES
47.6800 to 49.5800 BUSINESS RADIO
49.6000 to 50.0000 U.S. MILITARY

50.0000 to 54.0000 HAM RADIO 6 METERS

Search through those frequency ranges and see what you hear! Most Sporadic E Skip occurs from sun up to sun down, however some of the best sporadic E skip openings can occur well till midnight.


You might ask, what antenna do I need on my receivers to pick up this skip? Well, most people reporting activity have received low band skip just using a rubber ducky on a handheld scanner, however using a dipole wire antenna cut for 40 MHz will probably give you the best results.

Whatever you hear, whenever you heard it, be sure to post your findings and logs to the Skip / Tropospheric Ducting Forum on RadioReference.com.

Have fun!

Sunday, June 15, 2008

Decoding NOAA APT Weather Images

There are a lot of things in the radio communications hobby that are exciting... but for many monitoring satellite communications is at the top of the list. One of the more interesting satellite monitoring targets are the NOAA low earth orbit satellites, which fly in sun-synchronous polar orbits around the earth and continuously transmit satellite photos. These picture transmissions occur in the 137 MHz band and are easily monitored with a scanner and easily decoded with free software. In this post, I'll review how I was able setup a process to receive and decode these pictures using an AOR AR5000 Radio, a computer with a sound card, and free decoding software.

Currently, there are 3 production NOAA satellites, NOAA 15, 17 and 18. They transmit on the following frequencies:

NOAA 15 137.500
NOAA 17 137.620
NOAA 18 137.100

The transmission mode is FM, with a bandwidth of 30 KHz. There are very few scanners and communications receivers that have a IF bandwidth selection of 30 KHz, however you can still receive the signal using the standard mode selection of FM for your radio.

To get started, you will want to dedicate a receiver for satellite monitoring - the receiver should have a good outdoor antenna with a clear view of the sky. The easiest method is to use a discone antenna, or other roof mounted antenna. There are antennas that are designed specifically for the circular polarization of the NOAA Satellite signals, however a standard discone or other common outdoor scanner antenna should work fine.

Next, you will want to download and install the APTDecoder software package. APTDecoder is a free software package for recording and decoding signals transmitted by NOAA APT enabled weather satellites. It runs on Windows and is a very powerful tool for decoding the NOAA APT signals.

Your next step is to determine what your current station's latitude, longitude, and altitude is. This is important, since the NOAA satellites are in orbit around the earth, and you'll need to use APTDecoder to predict when the satellite passes overhead. Write these three pieces of important information down for input into APTDecoder.

Configuration of APTDecoder

After starting APTDecoder, launch the application and click Settings -> General Settings. You will want to enable the auto-recording and processing feature which starts the decoding process for you when a satellite comes into range.

Next, choose the Image Properties Tab and the Enhancements sub-tab and choose the Histogram equalize option. This will help to lighten the picture after decoding so it is more easily viewed.

There are a number of other features that can be enabled, such as auto radio control and more picture settings, but the above settings should get you started.

The next step is to define your ground station particulars. Choose Settings -> Ground Station, and enter your Latitude, Longitude, and Altitude. Then click Add, then scroll through the list to find your new entry and click Select.

Now that your ground station is configured, you'll need to download the latest Keplerian elements for the satellite orbits. Keplerian elements are 2 line text data sets which describe how a satellite is orbiting the earth. These are updated often and need to be refreshed to ensure accurate predictions on satellite passes. Click the Satellite -> Keplerian elements menu item, highlight the first URL entry, and click the Download button on the right. The modified timestamp should show an updated timestamp for the current date and time.

Now that you have configured the software, it's time to connect your receiver to the computer. If a satellite is actually overhead and in range, APTDecoder will start recording immediately. If this happens, just click cancel.

Connecting Your Scanner to the Computer

APTDecoder uses the sound card installed in your computer to decode the transmissions from the scanner. Connect an audio cable from the headphone or audio out jack on your scanner to the mic in jack on your sound card. Then, to set the audio level properly, choose the Tools -> Check audio level menu item in APTDecoder and follow instructions in the meter to set the audio level properly.

Decoding a Satellite Pass

With the application configured, APTDecoder is now tracking each of the 3 NOAA Satellites and is providing predication and tuning information to you in the interface. It is time to prepare for one of those passes and decode the transmitted data.

At the top of the APTDecoder window interface, you'll notice the phrase "Tracking NOAA-## on 137.620 MHz....." This top line is telling you the next satellite that is about to come into range (or is in range), on which frequency, and the specific time that the satellite will pass over your ground station. At the bottom, you'll see a line that says "Next: NOAA xx on 137.620 .........", this is the next satellite pass AFTER the one that is being tracked (sort of the "next, next" pass).

Reading the top line on the interface, tune your scanner to the frequency that APTDecoder says the next Satellite will be on. Remember, this line is telling you which satellite will be next, on which frequency, and when. In the following example below:

This tells us that NOAA 17 is next, transmitting on 137.620 MHz, and will come into range (AOS = Aquisition of Signal) at 17:06 UTC. The current time is 15:11 UTC, so we have about 2 hours before the next pass. To see where exactly each of the 3 NOAA Satellites are in relation to the earth, you can choose the Flat Earth Monitor tool (Tools -> Flat Earth Monitor).

To setup and decode the pass, tune your scanner to the proper frequency as indicated on the top line, plug in the audio cable, adjust the audio levels, and wait.

NOTE: Remember that NOAA APT transmissions on the 137 MHz band have a bandwidth of 30 KHz. If your radio has the capability to change the IF Bandwidth to 30 KHz, you should enable that setting. There are very few radios that have this capability (the Icom R9500, Icom R9000, and the AOR AR5000 are the ones I am aware that can), however it is reported that most scanners in standard FM mode (typically 15-20 KHz) will work OK, but don't expect a perfect decode unless you have a wider 30 MHz bandwidth.

When the satellite comes into range, APTDecoder will immediately start decoding, and you should begin to see each line decode and scroll. In the beginning of the pass, don't worry if there is a lot of noise, the satellite may need a few more minutes to get into range. The initial decode of the picture will be very dark looking, however after the entire pass finishes the decode will look just fine.

Each NOAA Satellite transmits two photos - a visible earth image on the left, and an infrared image on the right.

Start of decoding will look like the below. Don't forget, the initial picture will look very dark, however when the pass finishes the software will auto-process the image for proper light levels.

Still decoding...with the Flat Earth Monitor enabled showing the satellite transmit footprint around my ground station (you can enable this during the decode):

Finished. You can see both the visible image on the left, and the infrared image on the right.

That's it. Once that decode finishes the next upcoming satellite pass details will be displayed on the top line and you'll want to adjust the scanner frequency if needed.

I hope this was an enjoyable post, and that if you've never been able to decode NOAA Satellite transmissions this will be a good first step for you.

Friday, May 30, 2008

Progressing the service tagging of frequency and talkgroup data

As many are aware, back in January of 2008, we released a new set of functions to allow our database administrators to begin tagging frequency entries and talkgroup entries in the database with a number of new fields, mainly location information, service tags, updated alpha tag functions, and other attributes. One of the most important components of those new functions were service tags, which is a predefined set of 30 different tags that can identify how a frequency or trunked system talkgroup is used.

One of the most important reasons why service tagging has been released is to prepare the RadioReference database for the eventual ability to respond to more natural language queries, such as "show me all fire dispatch frequencies in my area." This is an important distinction from how most reference sources are queried today and should speed the rate of innovation and delivery of services from RadioReference.com.

Tagging all new and existing frequencies and talkgroups in the database is a tedious task, and to facilitate the adoption of tagging, RadioReference is now going to allow any registered user on the RadioReference.com Web site the ability to tag any frequency and talkgroup with one of the predefined 30 tags if a tag does not already exist. This does not mean that our admins are not doing their jobs, but it does mean that they need assistance in tagging existing data that is very extensive and very tedious. 170,000 people are better than 80 to get this structured and extensive process completed.

Expect the release of this new functionality to happen the weekend of May 31st 2008. For those registered users who are interested in participating, please see the Services Tags and Guidance for Use article, which outlines how tags should be implemented.

Your help is needed, and we look forward to seeing the results!

Friday, May 23, 2008

Explaining the Data Removal Policy Change on RadioReference.com

It is well known to many members of RadioReference.com the data removal policy that was put in effect around the 2002 time frame. At that time, the political climate in the United States was at times very worrisome - especially after September 11th. After some drawn out discussions with multiple people within the Federal Government and US military, I decided that it was in the best interest of RadioReference.com, and myself, to allow US Federal and Military officials an opportunity to formally request that I remove data from the site, only under certain conditions. Basically, an "out", and the ability to stay off the radar of some folks that were looking to cause trouble. It is important to note that policy did not under any circumstances provide for the removal of data from the site for state and local government, or businesses, even though we had had received many requests to do so.

At the time, many wondered why I "caved" in to the US Military and Federal government, and I was strongly criticized for implementing this policy. I even wrote a lengthy position statement that helped explain the approach we were taking. However, in looking out for the best interest of RadioReference.com community and my family, with the political climate as it was at the time, I had decided to implement a removal policy to keep such a large target from becoming "shot at."

Moving forward though, now that the political climate has calmed and it has been very apparent that the 10 or so requests that I had to remove data did nothing to actually remove the information from the public domain - and frankly it is a well known fact in the security industry that security-by-obscurity does not work. Therefore, effective May 19th 2008 I made the conscious decision to rescind the policy and not remove any data from the site unless ordered to by a court that has jurisdiction over the site.

I'm sure that even this "policy change" will result in criticism, and I welcome the discussion. But remember, at the end of the day if something is important enough to be requested for removal, then it is important enough to either be encrypted or not broadcast over the air.

Tuesday, May 20, 2008

Dayton Hamvention 2008

How much more relevant could a first post to this blog be than to talk about Dayton 2008. For those that don't know, the Dayton Hamvention is the worlds largest convention for Amateur Radio Operators and Radio Communications enthusiasts. Each year, I've always "wanted" to attend, but never had the time or patience to sit down and plan a trip. Well, this year was different as I had some time, enough frequent flier miles, and patience to make the trip. At the last second, I decided to make plans to attend.

I arrived on Thursday into Dayton at around Noon, and promptly drove out to Columbus to visit Universal Radio's facility in Reynoldsburg OH. Since I was 12 years old, I used to gawk at their catalog and dream about owning a room full of HF radio equipment - so it was only natural for me to head out there and check out their showroom. Later that evening, I had dinner with Rich Barnett, President of ScannerMaster.com who RadioReference has a well established relationship with, and Gommert Buysen, the author of the popular Butel line of scanner programming software. After a fantastic steak, a Martini, and two bottles of wine, it was time us hit the sack and rest for the next day festivities.

I arrived at about 9:00 AM at the Hara arena and was struck by two things - the sheer amount of people that were participating, and how much of a dump the Hara arena is. It was evident that this event was easily 10 times larger than I had anticipated, and the Hara arena probably bulges at the seams when no one is there, so the place looked like it could come down in a cloud of dust at any minute. I immediately bought a ticket and decided to peruse the outdoor flea market first so I could keep and eye on the building's structural integrity before entering. I didn't buy anything, but it was fun seeing all equipment for sale.

At the flea market, I was shocked at how many people were selling stuff, and how much junk was out in the lot. After two long grueling hours I headed in-doors to the ScannerMaster booth to spend some time there to meet some of our regular members and administrators. I wasn't disappointed. Almost immediately we were non-stop bombarded with RadioReference subscribers and admins. Since I have never had the opportunity to meet any of the subscribers (and our admins) - it was a refreshing and very rewarding experience. Mark Meece, Tom Swisher, Chris Dees, Mike O, and numerous others all spent some time at the booth. I also got to speak with many folks that had never heard of RadioReference.com, and those who were purchasing a scanner for the first time. Cool!

After working the booth for a few hours, I headed out to see everything indoors. My first stop was by the GRE booth, where I met the legendary Don Starr of Win96/Win500 Software fame. Don had to be the best dressed buy at Dayton, and was demoing his fantastic software suite for the GRE Scanners. I've spent a lot of time working with Don online, so this was a special treat. Next, I went and twiddled the knobs on an Icom R-9500, saw the line-up at the AOR booth (the new SR-2000A is really cool), and stopped by the RF Space booth to review their SDR (Software Defined Radio) line-up.

All in All, Saturday was the same as Friday, with lots of shaking hands, fighting crowds, and looking at radios. I stopped by the Batlabs table to meet Alex, PJ, and the other Motorola equipment crew. In the end, I dropped some cash for an RF Space SDR-14 panoramic receiver and prepared for my Saturday afternoon flight home.

In summary, the show was far more than I expected, and I most definitely plan on attending next year!