Category Archives: Aviation

Photos of a B-17G Radio Operator Position

I had the pleasure of visiting the Champaign Aviation Museum recently and examining their under-restoration B-17G, “Champaign Lady”. Actually, the term “under-restoration” is incorrect. In actuality, the Champaign Aviation Museum is effectively building their B-17G nearly from scratch—quite an undertaking but one that the volunteers are performing skillfully and enthusiastically.

Being an amateur radio operator, shortwave listener, and would-be WWII-radio restorer, I was was pleased to see that Champaign Lady already has a nearly-complete radio-operator position installed, between the bomb-bay and the waist-gun section of the airplane. As a B-17G would have had during the war, Champaign Lady features a BC-348 liaison receiver and morse-code key mounted on a desk on the port (left) side of the bomber and a stack of AM/CW Command Set transmitters and receivers racked on the starboard (right) side of the bomber. In the photos, the top Command Set boxes are the transmitters and the bottom three Command Set boxes are the receivers. Of course, the BC-348 and the Command Set transmitters and receivers are fully tube-type, semiconductors having not yet been invented. During the war speedometer-type cables would connect the Command Set receivers to controls in the cockpit, allowing the pilot and co-pilot to control the Command Set receiver frequencies; electrical cables would have carried the receivers’ audio to the pilot and co-pilot and would have allowed them to change volume-level. The radio operator could transmit using the Command Set transmitters and could also switch the pilot or co-pilot intercom microphones to any of the Command Set transmitters to allow the pilot or co-pilot to broadcast to other bombers in the formation.

"Champaign Lady" radio operator position

B-17G “Champaign Lady” radio operator position; BC-348 liaison receiver on the port (left) side and Command Set transmitters and receivers on the starboard (right) side.

"Champaign Lady" BC-348 receiver

B-17G “Champaign Lady” BC-348 liaison receiver and morse-code key.

"Champaign Lady" Command Set transmitters and receivers

B-17G “Champaign Lady” Command Set transmitters and receivers on the starboard side of the radio room

During the war, the B-17G radio operator was an enlisted man, typically a sergeant or higher in rank. If in an earlier version of the B-17G, the radio operator was also responsible for manning a .50 caliber machine gun located in his section of the airplane. In all versions of the B-17G, the radio operator assisted the navigator by providing position reports based on radio fixes of beacons or radio stations. Additional information about the role of the B-17G radio operator can be found on the B-17 Queen of the Sky website.

And, for those interested, here is what Champaign Lady’s nose-art looks like:

B-17G "Champaign Lady" nose-art

B-17G “Champaign Lady” nose-art, starboard side; the port side features a mirror-image version of the same design

The Champaign Aviation Museum has a beautifully restored B-25J, “Champaign Gal”, in flying condition. Unfortunately, I’ve not been able to see if Champaign Gal features a restored radio operator position.

I have a BC-224, which is the 12-volt version of the BC-348 liaison receiver to put back into service as well as a BC-696A Command Set transmitter that I hope to eventually put back onto the air in the 80-meter amateur band. It would be wonderful if I had a B-17G in which to install these items—or even just room to build a replica B-17G radio operator position!


Eric McFadden, WD8RIF

ADS-B for SDRplay RSP1 and RSP2 now available

I was very happy to see the following message from Jon Hudson at SDRplay this morning:

“ADS-B for both RSP1 and RSP2 is now available for the Raspberry Pi 2 & 3 – you can get the software from downloads –

If you are an RSP2 user, make sure you use Antenna Port B when running ADS-B.”

This is great news as I’ve had a number of readers ask if the RSP series SDR was compatible with the DUMP1090 ADS-B system.

The SDRplay RSP2

If you have an RSP1 or RSP2 and either a Raspberry Pi 2 or Pi 3, this will be an easy, accessible way to experiment with ADS-B.

In the long run, however, I’d never devote an RSP as a dedicated ADS-B feeder. Why? The RSP is a very versatile, full-featured SDR and I wouldn’t want to tie it up with such a relatively routine, simple task.

Instead, I’d give ADS-B a try with the RSP, and if I liked it, I’d purchase this inexpensive FlightAware RTL-SDR dongle with a built-in 1090 MHz bandpass filter for $18.95.

Click here to read my recent article about setting up a FlightAware ADS-B feeder.

I’m always so happy to see such active application development from “Mom and Pop” companies like SDRplay and AirSpy. Just more ways to put your SDR to work for you!

Dan’s take on ADS-B with the Raspberry Pi B model

Many thanks to SWLing Post contributor, Dan Srebnick (K2DLS), who recently posted a detailed overview of his ADS-B installation on his blog:

Monitoring NextGen ATC (on the cheap!)

A key component of next generation air traffic control is Automatic Dependent Surveillance – Broadcast (ADS-B). The current FAA mandate is for all included aircraft to output ADB-B transmissions no later than January 1, 2020. But you don’t have to wait to receive and map ADS-B. There is a lot of air traffic to be seen.

[…]I decided to use a spare older RTL-SDR stick based on the RTL2832U and R820T chips. This USB device comes with a small antenna that I hoped would be good enough to get me started. It is not in any way optimized for the 1090 MHz signals that are used by ADS-B and is roughly 19 parts per million (ppm) off frequency. It cost a bit over $10 at a hamfest a couple of years ago. The designs have improved since the early models were offered. Newer models include a TCXO (thermally compensated crystal oscillator) for stability and accuracy.

I needed software to take signals from the RTL-SDR stick and plot them on a map. That software is “dump1090”, originally written by Salvatore Sanfilippo. I added an install stanza to the Makefile, along with a systemd service file, for a smooth system install. I also needed to install the RTL-SDR USB drivers. The complete installation runs “headless”, meaning no monitor, keyboard or mouse need be connected. Remote management can be done via ssh.[…]

Continue reading on Dan’s blog…

This is fantastic, Dan! Thank you for taking the time to share all of the code snippets you needed to do the installation on the Raspberry Pi B as well. Post Readers: if you have an older Raspberry Pi and RTL-SDR sitting on a shelf, use Dan’s guidance to turn them into an ADS-B feeder!

Click here to read my ADS-B feeder tutorial based on the Raspberry Pi 3.

Making a FlightAware ADS-B feeder with a Raspberry Pi 3 and RTL-SDR dongle

It’s been nearly a year since I acquired both the RTL-SDR (above) and Rasperry Pi 3 (below)r.

Remember when I made a plea for Pi 3 projects just last year––?

Although many of you suggested some great projects, I never actually got around to doing any of them. Now, don’t get me wrong––I wanted to, of course, but simply got involved with reviews, NPOTA, two months of travel…and, well, life.

Then, last week at the Winter SWL Fest, a common theme emerged in both presentations and discussions:  the numerous applications of the super-cheap, and thus super-ubiquitous, RTL-SDR dongle. In their engaging presentations, both Dan Srebnick and Mark Fahey––SWLing Post contributors and good friends––focused on the power of the RTL-SDR, expounding upon some simple, inexpensive applications in their forums. It was inspiring. Also, buddy Eddie Muro showed me just how easily an ADS-B receiver could be set up using an Android phone.

Back to the Pi. Though I was already aware the Pi 3 and RTL-SDR could be united to make an ADS-B receiver, watching Mark Fahey talk about how simply one could feed the FlightAware network with ADS-B data finally hooked me.  Why not, indeed? Here was fun to be had!

Mark preparing to woo his captive audience at the Winter SWL Fest!

I couldn’t get the idea out of my head, so Tuesday, the day following my return, I set the afternoon aside.  I rolled up my sleeves, and with my long-neglected Pi 3 and RTL-SDR, got ready to cook up a flight sensor.

I figured I was probably missing a component or two, and fully expected the process to be complicated, but decided I wouldn’t let this deter me. And guess what? I was wrong on both counts!

FlightAware ADS-B feeder recipe


If you only plan to use this SDR and antenna as an ADS-B feeder, you might go for the FlightAware Dongle and 1090 MHz antenna combo.


Note: I used this excellent PiAware ADS-B feeder tutorial to build my system–it’s detailed and doesn’t make the lofty assumption that you actually understand formatting cards, building disk images, and/or editing config text files.

Directions below are a highly distilled version of that tutorial. If you’re new to all of this, as I was, follow these directions instead of the above tutorial. Be aware that the directions assume you’re using the Pi 3 and a Windows PC to burn the image file.

  1. Download PiAware image7-zipSD card formatter, and the Win32 Disk Imager. Decompress all compressed files, install and note the folder locations.
  2. Register your username at FlightAware–presuming you don’t already have an account, of course.
  3. Use SD Card Formatter to format your MicroSD card.  Just make sure you’re formatting the correct drive, else you could easily wipe the wrong disk/card!
  4. Use Win32 Disk imager to write the PiAware image to your MicroSD card.
  5. If using WiFi, open Windows Explorer.  Locate text document called piaware-config on the MicroSD card, open it with a text editor, and locate the WiFi ssid and password locations. Per the config comments, edit them to match your WiFi system. Note that any special characters in both the name and password will require the use of quotation marks (again, noted in the config file comments). Save the file in the same location on the disc image.
  6. Remove the microSD card containing the PiAware image; insert it into the Pi 3.
  7. Connect the RTL-SDR or FlightAware dongle to the Raspberry Pi. Attach an appropriate antenna to the RTL-SDR. Note:  You’ll get the best results if you place the antenna outdoors with line of sight to the skies.
  8. Plug the Raspberry Pi 3 into a power source…and cross your fingers!
  9. Grab a cup of coffee, walk the dog, or listen to this 12 minute version of the BBC countdown; it could take at least this long for FlightAware to start receiving data from your ADS-B feeder.
  10. When you see this My ADS-B button in the header of FlightAware (see below), you’ll know you’re in business. Congratulations!  You can now watch the skies.

Feeding FlightAware

After my ADS-B receiver had been in operation for a while, I was very impressed with the data FlightAware was able to pull from my ADS-B feed. I was equally impressed with the number of distant aircraft I could receive with such a modest antenna––a number of them up to 135 miles from my location. Once I find a suitable outdoor location for the mag mount antenna, currently indoors, I expect the reception distance will increase significantly.

You can also connect to the live feed from your ADS-B receiver through your local network. Here’s a screenshot of my live data:

Future plans

At the moment, my ADS-B receiver is located indoors, in a south-facing window.

It works, but clearly isn’t ideal. Since the Pi 3 connects to my network via WiFi, I intend to install the full ADS-B receiver system into a small weatherproof case and mount it outside. My Pi 3 has no case, so I purchased an inexpensive one yesterday. I should be able to feed it power with an outdoor outlet…but I’m very tempted to experiment with making it solar powered.  To find out if this is a logical move, I need to observe and measure the power requirements first, and will be doing that in the next few weeks.

Meantime, I’m thoroughly enjoying watching the (amazingly busy) traffic in the skies…and the kid in me relishes it!

Thanks, Mark, for the great idea!

Have any SWLing Post readers attempted to build a solar-powered or outdoor ADS-B receiver? Please comment!

Guest Post: Colin’s retrospective on monitoring aeronautical communications

Map indicating location of the Shanwick OCA

Many thanks to SWLing Post contributor, Colin McKeeman, who at my request, kindly shares the following guest post:

Monitoring Aeronautical Communications – A Personal Retrospective View

By Colin McKeeman

Hopefully this article will demonstrate that this hobby involves so much more than just listening to ATC (Air Traffic Control) advising “Shamrock 105 you are cleared to land runway 28, report on finals”, etc. My life-long obsession with aviation communications has given me a considerable insight into the day to day working that this critical activity encompasses.

Despite my opening sentence, my first exposure to ATC jargon was during the early 1960’s when I discovered that local airport and over-flight movements could be monitored on a ‘tweaked’ domestic VHF receiver. I recall someone discovered that a well-known Dublin based audio retailer, could retune such sets to cover the aeronautical air band (108 to 137 MHz). As a consequence like- minded enthusiasts soon appeared at the airport carrying bulky portable sets where their regular station names on the dial had been hidden behind pieces of sticky paper with new designators ‘Dublin Centre’, ‘Shannon 131.15’, etc. Although more compact and dedicated air band receivers have been developed over the years and the basic mode of VHF transmission has remained almost unchanged, but this cannot be said of aeronautical short-wave (HF) communications.

Whilst the monitoring of local aircraft movements was a considerable enhancement to the ‘spotters’ hobby, the desire to get more advance notification of ‘interesting’ flights was always regarded as the ‘holy grail’. I can quite vividly recall the breakthrough when at 16:25 on Thursday, the 3rd October 1963, I first heard Shannon Aeradio (located in Ballygirreen, Co. Clare) working a Trans World Airways flight 741 on short-wave. This was whilst flicking across the SW1 band of my 1958 Philips, model B3X85U valve receiver (see image below).

1958 Philips, model B3X85U valve receiver

This set had two short-wave bands comprising, SW1 covering 2.54 to 7.45 MHz and SW2 spanning 6.9 MHz to 22 MHz. My reception was boosted by a length of bell wire jammed into the sets external aerial socket and pinned to the picture rail over my bed. Thankfully this was during the time when Shannon Aeradio still broadcast on AM as this set was not equipped with a BFO for single sideband reception. Suddenly it became possible to hear flights mid-Atlantic that might just route my direction, or better still land at Dublin or even Shannon (well worth the six hour round trip by car!). The next problem was that the aforementioned flight TWA741 didn’t provide identification on the tail number/registration of the aircraft involved, a key element for the ‘spotter’. (Sorry, now more maturely redefined as an ‘aviation enthusiast’!).

I then discovered that many airlines assigned their two tone SelCal (selective calling) codes to individual aircraft and since the ground based radio operator working the flights usually repeated the code when copying a position report, yet another identification opportunity presented itself. A database of code assignment was soon established, thanks to co-operative airlines and diligent monitoring of airport movements. Today these codes still provide a potential method of aircraft identification and even in cases where the SelCal may not be announced by either the flight or repeated by the ground operator, I now utilise a mode of the excellent ‘MULTIPSK’ software to decode and display the four letter characters on screen, for subsequent possible airframe tie-up. It should be noted that not all aircraft operators link the SelCal codes to specific airframes, as some allocate them to the flight number instead.

It soon became apparent that Ballygirreen was not the only aeronautical ground station that could be heard on HF and so monitoring of the oceanic activity in the various areas managed by, Prestwick, London (station sited at Birdlip, Gloucester – more on this later), Paris, Iceland, Copenhagen, Bodo, Gander, New York, Churchill, Sondre Stromfjord, Santa Maria, Madrid, San Juan, was soon being logged from their various ‘nets’. Today many of these stations either no longer transmit on HF or have been amalgamated into a single unit, e.g. Shanwick, which consolidated Shannon Aeradio and Prestwick (the London station having been previously replaced by Shannon in January 1966). By good fortune some of the major players on the North Atlantic shared common ‘Families’ of frequencies, namely Shannon, Gander, Iceland and New York in the mid-1960’s all transmitted on 5611, 5626, 5641 and 5671 mc/s and thus avoided the need for constant frequency hopping. It should be noted that Shanwick Radio is providing communication support from its location in Ballygirreen whilst the actual clearances and routing decisions are decided at the Oceanic Centre in Prestwick, Scotland, which are then relayed to the flights from the Co. Clare station.

These HF stations handle both civil and military flight movements however some agencies provide a dedicated service for their military traffic. This is particularly appropriate to the United States Air Force, who operate a vast net of HF frequencies and dedicated stations. Stepping back 20 or 30 years, activity on these channels was particularly frantic, a key facility of theirs being Croughton Radio, based in the U.K. at Barford St. John, operating on a primary frequency of 111.75 MHz, still heard today. Because they transmitted on single sideband, monitoring such activity on my old Philips set was frustrated by the lack of a BFO, although I did attempt to create a harmonic on the frequency with another set tuned appropriately. This workaround never proved to be very satisfactory but was sometimes worth the effort.

Gradually single sideband became the norm for aeronautical HF communications and so investment in a dedicated receiver became essential and I saved up for a Trio 9R-59DS and was lucky enough to supplement this with an old American BC-348 set during 1972, both of which are still in my attic. This necessitated the need to erect a more efficient external aerial and so I quickly set up a suitably matched half-wave dipole for the 5 MHz band down the length of the garden, much to the intrigue of the neighbours.

With the advent of home computing another dimension to this hobby presented itself, whilst still retaining use of the communications receiver. In the early days of commercial aviation their communications relied on W/T but by the time my monitoring commenced this had been replaced by R/T. However radio teletype (RTTY) had also become a key feature of communication between the aeronautical ground stations. Whilst Morse code could be copied directly with paper and pencil, a computer (on an in-line teleprinter) was required to copy RTTY transmissions. So in the mid-1970’s, with the help of some simple software, I managed to start decoding Ballygirreen’s remaining RTTY link with Santa Maria, their circuits to Prestwick and other centres having been withdrawn some years earlier. Shannon Aeradio transmitted RTTY to Santa Maria on 3250, 5813.5, 8145 and 11440 mc/s and received traffic from them on 5474, 10540 and 11468.5 mc/s. These circuits, like many others, fell under the umbrella of the worldwide AFTN (Aeronautical Fixed Telecommunications Network) and messages had to conform to standards and structure as laid down by the ICAO (International Civil Aviation Organisation).

An example of such a message, copied by the author from Shannon Aeradio on 22nd March 1995 sent to Santa Maria, in the Azores regarding a KLM flight number 781, where their request for a higher altitude was denied, is reproduced below. The italic text within the { } is my clarification of its structure and so does not form part of the original message:-

ZCZC SMA152 221258 {start of message no. 152 on the Shannon/Maria/A circuit at 12:58}
FF LPPOZOZX LPAZYSYX {flight safety mess’ for the Santa Maria Oceanic & ATC centre’s}
221258 EIAAZZZX {message filed at Ballygirreen at 12:58 on the 22nd}
TOD1252 {the key element of the message}
DFHM TA {selcal code DF-HM was transmitted on frequency TA, i.e. 5598 mc/s}
KLM781 RB TA MTNG F290 {the flight read back the message on 5598 mc/s & will maintain 29,000’}
EIAA RB TAQSYVA) {Ballygirreen read back on 5598 (TA) and advised flight change to 8906 (VA)}
NNNN {end of message signal}

Although the transmission of AFTN messages over HF have now ceased there is still much aeronautical activity to monitor, both on R/T or in the digital mode. Indeed the latest statistics from the Irish Aviation Authority shown that North Atlantic communications with Ballygirreen have grown by almost 9% when compared to this time last year, which represents contact with almost 945,000 flights for the first 10 months of 2016. Admittedly the format of the R/T air-ground messages have had their content shortened, especially as a result of the introduction of Controller Pilot Data Link Communication (CPDLC) procedures. Under this digital data transfer system, the ground station having established an initial R/T contact with the flight, all subsequent reporting is completed by data link and so further voice communication is dispensed with. Not all flights are CPDLC equipped and consequently R/T reports can still be monitored for the entire oceanic sector for a reducing number of operators.

Even though this precise mode of long range data communication may not be capable of interrogation by the average enthusiast, it is still possible to capture some of the aeronautical data bursts. For shortwave, this protocol is titled HFDL (HF Data Link), and for closer range the VHF equivalent is entitled ACARS (Aircraft Communications Addressing and Reporting System). To copy HFDL I use the ‘PC-HFDL’ software (Shannon operate on 11384 mc/s, plus others) and for the VHF data transmissions I use the ‘KG-ACARS’ software (the primary European frequency being 131.725 MHz). Incidentally, the United States Air Force utilise a similar HF based system called ALE (Automatic Link Establishment) but this tends to contain a lower level of information and transmissions are less frequent.

I hope this very brief overview gives you some idea of what attracts the current aviation enthusiast with an interest in communications and notably all without recourse to the Internet (except for initial access to the decoding software).

Many thanks, Colin!

If you would like further information, check out Colin’s HF blog or contact him directly at

As an aviation historian, Colin recently published a book on the history of the U.K. Birdlip communication complex, radio call-sign ‘London’ (mentioned in a post a few days ago).  The cost of Colin’s book including shipping to U.K. addresses, is €22. If you live outside the UK, contact Colin at the above e-mail address for a shipping quote.