HF air traffic from Seychelles 11300 kHz USB, on Tecsun PL-680
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- Опубликовано: 1 окт 2024
- Just a short clip of some air traffic from the Seychelles on 11300 kHz USB. I enjoy listening to HF air traffic, and my newly acquired Tecsun PL-680 seems to be very good at catching these. Seychelles Radio is a new one for me. Received in Johannesburg, South Africa, on 26 September 2024. I used a 5-metre wire as an antenna.
Catching HF air traffic requires patience, but it can be a lot of fun. Many airlines still communicate via HF radio (in other words, shortwave) when they are crossing vast oceans, like the Indian Ocean, in this case. But the frequencies they use are never busy all the time, so you have to listen patiently until you hear something, and you need a radio with SSB.
This video shows some transmissions I caught in a roughly 40-minute period, there were only a handful of very short transmissions. Still, I find monitoring these HF air traffic frequencies a lot of fun.
Picture of Seychelles International Airport, Mahé: By Gerard Larose, Seychelles Tourism Board, CC BY 4.0, commons.wikime...
I appreciate your effort in adding an aerial view of the Seychelles' airport and its sole runway for the preamble of this episode, Andre.
Makes me want to go island hopping in a small ATR 72-600 turboprop plane! ✈️🌍
HF and VHF radio are the most basic communications medium between aircraft and airport control towers. Larger, modern jet planes generally have satellite comms as a backup system. Pilots generally use the VHF Air band to communicate with the nearest airport tower control, but in the rare cases when they're out of range they would switch to HF.
Fun fact: the VHF Air band may be sitting just above the FM broadcast band frequency (108 MHz), but the Air band itself is always in AM mode, never narrow band FM.
The main reason for using AM is because FM transmissions have the undesirable "capture effect". If the aviation band used frequency modulation, the strongest transmission will dominate the channel and block weaker transmissions from more distant aircraft.
By using amplitude modulation, pilots and ATC controllers can listen to simultaneous background transmissions from other aircraft, in case of an emergency. Amateur ham radio operators who use the VHF 2m band on the other hand, use narrowband FM and not AM. 😊
That island airport looks very inviting indeed!
I read a very interesting article in the Wall Street Journal this week about GPS systems on planes being hacked, all around the world. This causes, among other things, the satellite communication systems on board to jam up. Which, in my opinion, just shows how important HF and VHF radio remains on aeroplanes. When all else fails, let's return to good old radio technology :-)
Here is the article: www.wsj.com/business/airlines/electronic-warfare-spooks-airlines-pilots-and-air-safety-officials-60959bbd I wasn't a subscriber, but when I saw this article I clicked on the subscribe button and they had a special offer of $2 per month for a year. So I signed up. Been very impressed so far, it is a very good newspaper. Not as partisan as some other US media outlets, like the New York Times (on the left) or Fox News (on the right). WSJ seems to be quite centrist and objective.
Not heard that will have to try, I used to listen to Atlantic HF air years ago.
Hey Matt, I have never heard this one before, it's not very busy, so you need to be really patient and wait for something to happen :-)
I remember this frequency was very popular 20 years ago, I could hear Cairo, Khartoum, Mogadishu, Addis Ababa, Entebbe and other aero stations such as Asmara, Aden or Nairobi. Sometimes they were booming in at my QTH in Roma, Italy. But since then the frequency has been less and less used in due time. I think they improved VHF coverage so no more HF aero traffic on 11300. Probably you heard them when VHF wasn't available.
Hi Piero, thanks for your comment. Interesting to hear about how busy this frequency used to be. Maybe VHF was down, as you say, although I think perhaps some flights crossing the Indian Ocean might use this frequency regularly. I'll keep monitoring it.
I've not heard that one as far as I know. But I have heard India on HF Airband. I suspect HF is more of a backup these days rather than a primary form of communication.
Hi Glen, I have also heard Mumbai on 8879, it is actually the one that I seem to catch most often. I think in some cases HF is just a back-up, as you say, but I think there are still instances when airliners are in the middle of vast oceans where they still rely on HF for some of their communication needs. The messaging system used on planes, ACARS, relies on VHF, so it only works overland. And satellite communication, from what I have read on some aviation blogs, while used by most airliners, is not ubiquitous, that is why a number of airliners still use HF radio when crossing oceans.
it's not so much a backup than a cheaper means of communication than satellite comms when out of reach of VHF. Still very much used. Commercial aircraft use low-bandwidth satellite data links for different purposes (including ACARS too, not to be confused with ADS-B), but not for voice comms.
Well, most if not all crews in commercial aircraft do have satellite phones, but these are used as backups.
Small, single or twin engined propeller aircraft generally don't have sophisticated communications equipment like satellite as they're very expensive. At the very least, small aircraft would have a VHF and HF radio, plus the mandatory transponder equipment. Nevertheless, VHF AM remains the primary means of communication with the ATC. At a cruising altitude of 30,000 feet an aircraft's radio transmission on VHF can reach up to 322 kms.
Aircraft waypoints are usually shorter than 800 kms from one waypoint to another and on trans-oceanic flights pilots would contact the nearest ATC every 30 minutes or so, to report their current position. Commercial flights always takes routes that are the nearest to populated areas with airports, should the flight need to be diverted in an emergency.
That's why there are no commercial aircraft overflying the Himalayas or the empty southern Indian Ocean. 🙂
@@F4LDT-Alain It's interesting that you mention the fact that it is a cheaper means of communication Alain. This thought did cross my mind also, I think there are many airlines with quite tight budgets and satellite communication can be really expensive. So it makes sense to me that some (maybe many) would continue to use HF radio. It certainly isn't just a back-up option, the many air traffic radio stations around the world that are still operating are evidence of the fact that HF radio is still used regularly by airlines. Lucky for us!
@@StratmanII Indeed. And when they are flying over empty oceans, they would need HF radio to contact the nearest ATC, which might be some thousands of kilometres away. Flights from Singapore or China to South Africa, for example, cross vast stretches of empty ocean. From here going east, after crossing Madagascar and before reaching Indonesia, there aren't really any islands or land anywhere near the flight paths. Not to mention flights across the Pacific, or flights across the Atlantic from Europe to South America.
Hi Andre, Bon soir as they would say in the Seychelles, my mother is a Seycheloise and I have lived in Victoria the capital for 3 years, a very beautiful place indeed, the airport is exactly like in the picture, the beaches are......paradise like
Bon soir Robert :-) What a wonderful place to have lived in! I would love to visit some day, the flight from South Africa is only about 5 hours.
@@swlistening I hope you visit the Seychelles some day I can assure you that you would enjoy every minute in that paradise....
@@robertvandervelde60 I am sure I will, it looks like a real tropical paradise!
Thanks Andre for the giving me an another stations to listen for…now if I just had the time and money…🙄….I like to be on one of those flights…😂😂😂!
Have a great day!
I will gladly join you on one of those flights to the Seychelles! Looks like a dream destination.
Woah! It's cool to hear something from the Seychelles after the BBC relay that closed in I think 2014.
Indeed! These HF air traffic signals gives us DXers the chance to hear some interesting locations.
@@swlistening I like to hear the Gander Radio signals a lot (not the volmet. Also, RUclips notified me 9 seconds after you commented. Usually it takes two minutes!)
@@theshortwavearchive35 Mach 1 on RUclips 🤣 I have also caught some HF air traffic from Mumbai, Chennai, Manila, Santa Maria (Azores) and Shannon. Santa Maria and Shannon were very weak though, the other three were listenable. I really enjoy HF air traffic. I do also enjoy catching the Volmets 😀Anything to do with air travel is fun for me.
Great catch!
Thanks!
Hello André, this is a fantastic catch, one more to add to my wanted list, congratulations! 😁
Did you check what distance does this make from you?
The tones we hear are the SELCALL tones, selective tones used when they want to talk to a specific aircraft. They normally assign a specific tone combination to each aircraft entering their control area and announcing itself, it is sent at the end of the transmission and picked up by the receiver on the plane. After this, they can "call" a specific airplane by issuing this tone at the beginning of the transmission.
Ground-to-air transmission from Shanwick are a fairly easy catch from here, but I've also caught ones from Canada and the Eastern Coast of the US while in Brittany. These are all quite interesting to listen to but as you point out, you have to be on the right frequency at the right time.
Hi Alain, thank you so much! I was quite excited about this one, because I have tried this frequency many times in the past, but I have never heard anything. As you say, the thing with the HF air traffic frequencies is that you simply have to listen at the right time, but it's kind of impossible to know when the right time is :-) These transmissions are always very random. So what I learned from this specific catch is that I just need to park on a frequency and listen for a very long time. Eventually something might happen.
Thanks for the explanation about the SECALL tones, I did not know about that. I hear these tones often when I monitor HF air traffic, but I never really knew what they meant.
The Seychelles are not that far away from me, flight time is only five hours, and the distance is about 4000 km, so not very far at all. But still, this is a nice one for me. I also catch Mumbai quite often these days, that is a bit more distant, about 7000 km. But my best HF air traffic catch was Manila, I caught that a year ago, I have a video on my channel. That is a distance of 11000 km. Here is the video: ruclips.net/video/scgqIp4dA_Q/видео.html