Category Archives: Guest Posts

Guest Post: National HRO-500 Unboxing and Initial Tests

Many thanks to SWLing Post contributor, Dan Robinson, for the following guest post:

HRO-500 Unboxing and Initial Tests

by Dan Robinson

It is amazing that in these days of waning shortwave broadcast activity, there are still those occasional time capsules — radios that appear on the used market via Ebay or private sales that are new in the box or close to it. Think of it — after 50 or 60 years, these fine examples of radio history can still be found, complete with their original boxes, shipping crates, manuals and accessories.

We have seen a number of these in recent years. Several years ago, a Panasonic RF-9000, one of the Holy Grails of radio collecting, appeared on Ebay, in new opened box condition. As rare as that was, it’s even rarer to find tube or solid state communications receivers from the 1950’s and 1960’s. Such is the case with National HRO-500s, which were considered high level receivers when they came on to the market in the mid-1960’s.

In 2016, a seller in California advertised a great rarity — a HRO-500 that he said he purchased in 1967, complete with its original shipping crate.

It was said to be in new/unopened condition, which of course raises concerns about the unit itself since it has never been used since leaving the factory. While that radio apparently sold (the asking price was $2500), I was astounded to recently see another HRO-500. It was not in New/Unopened condition, but the closest one comes to it. Among a collection purchased by the seller, the radio was in its original crate, inside of which was the original box with the original National Radio Co fabric cover, with original strips of fiberglass insulation. The manual is still in its plastic wrap.

I decided to do a video for SWLing Post readers, and provide some still shots, as this time capsule of radio history was opened (this was likely only the 2nd or 3rd time it was opened since leaving the factory, the last time by the seller for photography for the Ebay ad.

The good news — many HRO-500s on the used market exhibit failure of the PLL lock circuit. While the PLL lock light on this particular radio does not light up, its PLL does operate on every band. This radio arrived with one metal cap for the MODE knob missing, so I’ll be searching for a spare. And the dial calibration clutch knob appears to be frozen, another minor issue that does not impact operation of the radio.

All in all, this was a fantastic find and I hope SWLing Post readers enjoy the video and stills:


Click here to view the video on YouTube.


Thanks for sharing your notes, photos and video, Dan!

The National HRO-500 is a gorgeous radio and it looks like you’ve got a prime specimen. I’m so impressed it came with the original wooden crate, exterior box and radio box! Amazing.

We’re looking forward to your assessment of the HRO-500 once you’ve have it on the air a while.

SWLing Post readers: In March, I had the good fortune of visiting Dan Robinson’s home and taking a tour of his impressive radio collection. I took a number of photos with Dan’s permission. I’ve been incredibly busy as of late, but as soon as catch my breath after travels, I’ll post the photo tour. I’ll also post photos from our tour of the NSA museum in Fort Meade, MD. Stay tuned!

Tony performs a quick LNA4ALL test

Many thanks to SWLing Post contributor, Tony Roper, who shares the following guest post which originally appeared on his blog, Planes and Stuff:

Quick LNA4ALL test

by Tony Roper

Despite the best efforts of the Royal Mail service, I have been able to get my hands on a Low Noise Amplifier created by Adam at LNA4ALL. The Royal Mail showed just how useless it is, when the parcel arrived here in the UK in just 11 hours from Croatia on February the 14th, but then not getting delivered to me until March the 14th – yes, one month! There is no surprise that courier companies such as DPD and Hermes are getting more business than the Royal Mail – they are bloody useless.

Anyway, the reason for the purchase is for a later review on an AIS dongle that I will be testing, but which has unfortunately been possibly damaged before getting to me.

So, as I had some time to spare I thought I’d run a quick test on how the LNA performs against the claims that is shown on the LNA4ALL website. For the test I used a quickly built 12v to 5v PSU that was connected to a Maplin bench PSU and also a Rigol DP711 Linear DC PSU where I could ensure a precise power input. As it was, it was good that I used the DP711 because my quick PSU was only chucking out 1.2v at connection to the LNA4ALL, despite an unconnected output of 5v – some work needed there I think.

Despite this lower power the LNA4ALL still worked with just the 1.2v input, though the results where not as good.

Other equipment used were a Rigol DSG815 Signal Generator and a Rigol DSA1030 Spectrum Analyser (no longer available), along with various Mini-Circuits shielded test cables. The Rigol equipment I purchased from Telonic Instruments Ltd last year.

Below then is a table that contains all the relevant data. As you’ll see the Gain claim is pretty much spot on with some being over. Just a couple of frequencies are below that which is claimed, especially at 28 MHz.

LNA4ALL Frequency data

A couple of things to note.

Firstly, somehow I managed to miss testing 1296 MHz. I obviously didn’t put it in the table in Excel before I started ? Also, the DSG815 only goes up to 1.5 GHz so I couldn’t test above that.

Secondly I ran a test for the AIS centre frequency of 162 MHz, for which there was no comparison to the LNA4ALL data. A gain of over 24dB though shows that the LNA would be perfect for those of you with AIS receivers that may want to get better reception. To prove the theory I compared the LNA reception against data without it connected to the NASA Engine AIS receiver that I currently use. In ShipPlotter I average a max range of around 15nm without the LNA, but with it connected this increased to around 22nm. The number of messages received also tripled as it was able to dig out the weaker signals.

The NASA Engine isn’t a bad receiver, but it is a frequency hopper rather than a dual monitor, and so it changes between the two AIS frequencies every 30 seconds (161.975 MHz and 162.025 MHz). I suspect a dual monitor would give better message numbers and range.

Below is a graph made using the excellent software by Neal Arundale – NMEA AIS Router. As you can see the message numbers (or sentences) for over an hour are pretty good – well, it is a vast improvement on what I used to get with my current “temporary” set-up, with 419 messages received in an hour. The software is available at his website, for free, along with various other programs that you can use with AIS. If you’d rather not use ShipPlotter he has created his own AIS Decoder which can be linked into Google Earth and such like. Visit his website for more information.

My antenna isn’t exactly top-notch. It is at a height of just 4 metres AGL in the extension loft, and it is made from galvanised steel angle bead used by plasterers to strengthen corners prior to skimming – this I cut down as a dipole for a target of 162 MHz. As usual with my trimming of antennas, I cut just too much off and ended up with it cut to 161.167 MHz. It gives a VSWR of 1.018 and Return loss of 40.82dB, with 162 MHz being approx. 30dB Return loss which equates to 1.075 VSWR – that will do.

Also, as I live right on the coast, about 50 metres from the sea, I’m practically at sea level, which doesn’t help much with range and signal reception either. Despite this the antenna produces great results, though it is just temporary until I can get a new homebuild up on the roof.

VSWR reading for the homebrew loft AIS Antenna

The LNA4ALL retails at various prices depending on what option you go for. I went for the aluminium box version so it was around £54 including the delivery. I had looked at a Mini-circuits equivalent, and when it looked like the LNA4ALL was lost I did actually order one. But this was nearly twice the price, and seeing as the LNA4ALL contains many components from Mini-Circuit I doubt it is any different really.

All in all the LNA4ALL is all you need to boost your weak signals – couldn’t get any more all’s in ?.

Many thanks for sharing your quick test of the LNA4ALL, Tony! Post Readers: if you’d like to read more of Tony’s work, check out his blog, Planes and Stuff.

Charlie reviews the Tecsun PL-365

Many thanks to SWLing Post contributor, Charlie Wardale, who shares the following guest post:

Tecsun PL-365 Review

by Charlie Wardale

I have had this receiver for over 6 months now, and whilst not using it every day, I have used it enough to have an informed opinion of it’s pro’s and con’s.


A quick description of the receiver for those who have not heard of it.

The receiver is of an unusual design, more like a hand-held transceiver, measuring 53(W) X 159(H) X 26(D) mm. It naturally fits in the hand, with the thumb resting easily on the thumb-wheel tuning. The buttons on the front are for a number of alarm and display functions, SSB selection, and ETM, along with band selection and up/down keys. The inclusion of SSB makes this quite a unique radio, and certainly interesting to use when out and about.

It is supplied with ear buds, faux leather carrying case, the plug-in MW bar, and instruction booklet. A manual is also available to download.

As can be seen from the picture, the receiver sports a telescopic antenna for FM/SW, and a unique plug-in MW ferrite rod antenna, which is rotatable in its socket.

Band coverage is as follows:

  • FM 87~108 MHz
  • MW 522~1620
  • SW 1711~29999 kHz

Long Wave is also available and on mine was factory set to be included, but if not, it can be made available by the menu options.

Like many of Tecsun’s latest receivers, the PL-365 includes the ETM function, which stands for Easy Tuning Mode. With this, you select the band (MW,FM,SW), press ETM, and it loads into a local memory, all the stations that it detects. These do not over-ride any of the main memory that may have been already used to store stations. It is specific ‘ETM’ memory. Once the detection process is completed, the tuning wheel is then used to select each of the stations detected. This is an extremely useful feature on this receiver, as it doesn’t have keypad entry for frequencies. And band scanning using the thumb wheel in 5 Khz steps can get tedious! Of course, ETM will have to be repeated a number of times during an extended listening period as stations come and go.

Initial Listening Tests

My first port of call on starting the listening tests was FM, to judge how it received the local and national broadcasters, and to see how stereo broadcasts are received. Incidentally, I changed the supplied ear buds for some in-ear types which I find stay in place better. All national broadcasters (BBC) and local radio stations (BBC and independent) were detected well. Received audio on the built in speaker is pleasant, but as can imagined from such a small speaker, not of great range. However, stereo broadcasts from BBC Radio 3 (classical music) and Classic FM, sounded excellent using the ear buds. At night time, some further afield stations are detected, so the FM sensitivity is good.

When I conducted these initial tests, it was evening so I decided to give the MW band a whirl as well. I fitted the MW bar antenna into it’s socket atop the receiver, selected MW and hit the ETM button. After a couple of minutes, the detection process stopped and a great number of stations had been detected. Going through them, not only were there the local (and not so local) UK MW stations, but some from much further afield such as Bretagne 5, SBC in Riyadh, and RNE Radio 5 in Madrid. By turning the ferrite antenna, it was possible to peak these stations nicely.

So now to SW. As can be seen, SW coverage is full range from 1711 – 29999, excellent for a receiver of this price range. For this initial test, listening was carried out in the early evening, in the garden, during the summer, so the higher bands were where most of the action was. Following a similar pattern to the FM and MW test, the telescopic whip was extended and the ETM button pressed. On stopping detection, a total of 65 stations were noted. One or two of these, it later proved, were images, but for the most part they were all receivable signals. The treshold for detection is quite low, so some stations are barely audible under the noise, a testament to the sensitivity of the 365. All the major stations were received well, such as VOA on 15580, Saudia Arabia on a number of frequencies, CRI of course, over numerous frequencies. And in between, stations such as CNR1 (China National Radio), the regional Chinese service, and R Australia on 12065, BBC from Singapore.

After this, I did some listening on the 20 and 40m ham bands. To do this is slightly tricky, as it entails coming out of ETM mode by pressing the VF/VM button. This puts the radio into frequency mode and the thumb wheel is then used to get to the correct frequency. The USB/LSB button is then pressed and once a station is found, press the BFO button. The tuning thumb then becomes a BFO fine tune, and the amateur radio station can be tuned in accurately. It is tricky to start with but you do get used to it and amateur stations can be tuned in well. I received a number of European stations on 40m and European/Asian ones on 20m. So again, sensitivity is good, even though this is just using the whip antenna.

Long Term Listening Impressions

Over the months between those initial tests and now, I have done a number of hours listening using this radio, on both the MW and SW bands. I especially like it if I am out for a walk in the country near us as its handy to carry in the pocket. One Sunday I listened to the whole hour of a VOA broadcast on 15580, whilst wandering along the Lincolnshire foot paths. And it is also a nice radio to do a bit of casual listening from the armchair of an evening, when the TV is on but of no interest. This way I have enjoyed many a broadcast from VOA, RRI and the BBC using the ear buds. It’s also nice to tune into the Celtic music of Bretagne 5 during the evening on MW as a change from the fair on BBC Radio 2 or 3.


Would I recommend this radio? Yes I would, whole heartedly. For what it is designed to do, it does very well. Could it be better? Of course. A keypad would be nice, an external antenna port would be great and so on. But it was designed to be a general coverage receiver, in a small, hand-held package, and for that it receives top marks.

Many thanks for your review, Charlie! I agree with you that the PL-365 is ideal, in terms of form factor, for radio listening while on long walks and hikes! It is certainly an excellent portable.

The Tecsun PL-365 can be purchased from Tecsun Radios Australia and occasionally on eBay (click here to search).

Guest Post: Shortwave Recordings from Mount Kilimanjaro

Mount Kilimanjaro (Photo: Chris Johnson)

Many thanks to SWLing Post contributor, Chris Johnson, for sharing the following guest post:

Shortwave Recordings from Kilimanjaro

by Chris Johnson

Last month, I took a trip of a lifetime to Tanzania Africa to Climb Mount Kilimanjaro: Africa’s highest point and the world’s highest free standing mountain. It is also known as the “Rooftop of Africa” its summit stands at 19,341 feet or 5895 meters.

With this high elevation I figured that I could pick up a multitude of shortwave signals that I would normally not receive at lower altitudes. So I packed my Sony ICF- SW7600G to capture recordings of various signals, some common, others not so common.

Each night I unpacked my radio and extended the reel-wire antenna and scanned the bands. I came across an assortment of stations that I normally do not hear back home in the USA, but some were quite familiar such as the BBC, Radio Romania, and DW which had Africa as their target. In some cases their broadcast was targeted for Asia.

Below is a map of our trek along the Lemosho route and the camps where we stayed are listed with the recordings and the elevation (in meters) of each camp. The higher we climbed, the signals received were sometimes stronger but the surrounding mountains also limited the reception of others. I did find that the bands were congested with signals from stations that spoke Arabic, Swahili and Chinese, not surprising considering my location. For the purpose of this blog I only included the English speaking stations except for a few.

Unfortunately, the critical weight in our day packs was closely monitored and we could carry only the essentials on our climb from Barafu to the summit so I could not record at the summit of Uhuru Peak. Additionally, our time up there was limited to 15 minutes due to the lack of oxygen at that altitude. Below are selected recordings at each of the camps on the Lemosho route. Enjoy.

Click to enlarge

Mkubwa Camp Elevation 2650 meters 8 January 2017

Mkubwa Camp Elevation 2650 Meters BBC 7445 khz 1840Z 8 January 2017:

Shira Camp II Elevation 3850 meters 9 January 2017

Shira Camp II Elevation 3850 Meters SW Africa Radio League 4895 Khz 9 January 2017 1645z:

Shira Camp II Elevation 3850 Meters DW 9820 KHZ 1600z 9 January 2017:

Shira Camp II Elevation 3850 Meters 1 9 2017 1538z Channel Africa 9625 kHz:

Shira Camp II Elevation 3850 Meters All India Radio 13695 khz 1835z 9 January 2017:

Baranco Camp Elevation 3900 meters 10 January 2017

Baranco Camp NBC Zambia Radio 11 January 2017 5915 KHZ 0317z:

Baranco Camp 3900 Meters Voice Of Nigeria 7255 Khz 1 10 2017 1915z:

Karanga Camp Elevation 3995 meters 11 January 2017

Karanga Camp Elevation 3995 Meters All India Radio 13695 Khz 11 January 2017 1753 Z:

Karanga Camp 3995 Meters Voice Of Nigeria 7255 Khz 1812 GMT 11 January 2017:

Karanga Camp 3995 Meters Channel Africa 9625 Khz 11 January 2017 1735z:

Barafu Camp Elevation 4673 meters 12 January 2017

Barafu Camp 4673 Meters BBC Asia Target 7465 Khz 1429z:

Barafu Camp 4673 Meters All India Radio 13695 Khz 1 12 2017 1044 Z:

Barafu Camp 4673 Meters Radio Romania 15150 Khz 1210 Z:

Chris: thank you so much for taking the time to write up this guest post and share your excellent recordings and photos. Amazing!

Post readers: I don’t know about you, but I’m inspired and ready to pack my bags and do some shortwave travel!

Click here to check out other posts by Chris.

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.