Anatomy of a low frequency aviation radio beacon

There's a reason for that: being channelized ensures you can tune quickly to the right frequency and AM ensures that if two radios transmit simultaneously, the receiver can still hear and read both transmitting radios. That is almost impossible with FM. Also, readability remains better in low signal conditions than with FM.

 

Being an older pilot I see trouble on the horizon dismantling the old guard. People just don't understand how vulnerable GPS is and they won't until its too late. I used to do a lot of long haul over water and having an ADF was a minimum piece of safety equipment. Having a list of NDBs and AM commercial stations afforded the ability to triangulate a position. I also wonder how many pilots today can run a sextant. I know most sailors have lost the ability now. One good solar storm equal or better than the Carrington event will show the error off our ways especially now that out magnetosphere is weakening quickly. Anyone seen whats going on with the Atlantic anomaly lately? Its double in size in less than a decade and is a good indication of how hard we will get hit by solar storms we brushed off not long ago. That also makes me think of the latest news on quantum computing that they are finding the increase in cosmic rays due to our weakening fields is making such computing impossible unless they figure out how to shield them. All this shows how we are heading in the wrong direction in our reliance on critical systems.

 

Like @WQ2H posted, below is my Lofer Listener list from west central Florida on a quiet winter night in 2016. Rig was an Icom IC-781 (a superb rcvr down there) and an aluminum tube short Marconi vertical about 45ft high with top load T wire resonated for 1830 kHz.

As @K4RGN posted, the big gun beacon CLB was loud all the way down here on the Gulf of Mexico. Other notable DX was BRA on 379 kHz from Asheville NC, XW Flemingsburg KY 400, and hearing YHN on from Hornepayne Ontario (!) underneath CH in Charlotte SC on 329, and the WD2XSH/31 ham beacon on 478.

Of course the blowtorch down there is Medi1 Radio on 171 kHz from their Nador xmtr site in north Africa with 1.6 MW QRO and a multi-tower array pointed roughly our way over the pole.

Starting 0200Z 12/16/2012 (UTC)
KHZ Callsign and QTH
171 Radio Mediterranee International Nador Morrocco (1600 KW!)
198 DIW Dixon NC (12/24/2016)
206 VNC Venice FL
216 CLB Wilmington-Carolina Beach NC
221 FX Fort Lauderdale Executive
221 OR Orlando
230 ULC Cayo Largo del Sur CUBA
257 SQT Melbourne-Satellite FL
260 MTH Marathon (Key) FL
275 FPR Fort Pierce FL
280 MQW McRae-Wheeler GA
283 UZG Zaragoza CUBA
326 PKZ Pensacole-Pickens FL
329 CH Charleston SC
329 YHN Hornepayne Ontario
332 FIS Key West - Fish Hook FL
341 FM Fort Myers
344 ZIY CYM Georgetown - Grand Cayman
344 IWJ Blakely GA
344 JA Jacksonville FL
360 PI St. Petersburg FL
368 TP Tampa FL
376 ZIN Matthew Town-Great Inagua Bahamas
376 BAXLEY GA voice modulation message = "Baxley Municipal Airport automated altimeter three zero one two" at 0214Z
379 BRA Asheville-Broad River NC
382 APT Jasper TN
385 KLT ???
388 AM (huge sig!) Tampa FL
389 DDP San Juan-Dorado PUERTO RICO
400 XW Flemingsburg KY (12/24/2016)
408 SFB Orlando-Sanford
432 IZN Lincolntown NC (12/22/2016)
478 WD2XSH/31 ham beacon from VT (?) RST 549 0400Z
510 HMY Lexington-Muldrow OK
521 GM Greenville-Mauldin SC
526 ZLS Stella Maris BAHAMAS (under splatter from Cuba etc on 530)
529 LYQ MORRISON-ROSEANNE TN (under splatter from Cuba etc on 530)

 

That's really not valid. You cannot "read multiple VHF AM transmissions transmitting at once. They're almost NEVER on the same frequency (even though they're supposed to be) there's always hetrodynes and ATC always has to tell everybody to stand-by when it gets messy.

When there's "doubling" (or tripling) someone always says "Blocked" because transmission is truly blocked.

NBFM would have worked but the technology just wasn't there and there was no real benefit. VHF SSB would have been better but no manufacturer could have produced the stability required until many years later. (and we'd still have the same problems)

It hasn't changed because of MONEY. The cost of changing like the land mobile services has (several times) over the years would have been cost prohibitive since government would have had to mandate it. and the ICAO would have had to "buy-off" on it (that wouldn't have happened)

And, any new system would have had to be operated side-by-side with the previous systems. The airlines and military and the ICAO countries simply wouldn't have played along. And it wouldn't have been practical anyway

That's what is essentially happening now with NEXTGEN. It has already started with CPDLC for over water position reporting. HF SSB will be a "thing of the past" and will become a back-up and eventually a not required ("MEL'able") piece of equipment.

For example, right now, today, one can fly from Seattle to Anchorage, or Fairbanks, AK and not actually speak to (Canadian) Enroute ATC via radio except for a quick initial radio check. It's all done via CPDLC (Contoller Pilot Data Link Communications) Anchorage Center told me that they could do it also but the "turn-on date" was somewhere in the future. (Is it on now Bryan?)

Also a flight can leave the west coast bound for Hawaii and after crossing the "coastline".....then switch from VHF voice communication directly to CPDLC and not speak to anyone (except for that ARINC HF radio/SELCALL check) until within VHF range of the islands.

Bryan, N3FAA, can verify that this is already planned for the US Enroute structure. If I am not mistaken, it's going to be "turned on" pretty soon if it isn't already on now. Voice communications is simply not needed for routine ATC in the enroute structure.

I see a time when all ATC instructions will be transmitted and acknowledged via "text-message". If there's any talking to be done, it will be via a digital voice link.

All the aircraft will probably still need to have a "Guard" (121.5, 243.0) receiver but the only ones that talk on Guard is the NAVY!!

 

Pilots couldn't use a sextant in the 60's The USAF C-141A had a sextant port in it and the navigators were the only ones trained to use it.

We used the sextant port as a vacuum cleaner. I started flying the C-141 in 1981 thru about 2000....... I had a great time using the HF radios on all bands!

Just about all the hams I talked to asked me if I was the "Radio Operator" (or the navigator)

We stopped carrying Navigators for routine overwater flying in the late 70's (only using them for tactical airdrop) And I cannot say when Radio Operators went away....never met one! Probably at the end of WWII, way before I was born.

That might have worked in the 1950's, you could probably find your position within 50 miles (depending on atmospheric conditions)

Try that on the NAT or Hawaii Tracks now and it would not only get you violated, you would also risk a mid-air collision.

Overwater flying since the 60's has used INS/IRS + Loran or Doppler and now, GPS. But the newest IRS (Inertial Reference Systems) are pretty accurate even without GPS and they cannot be jammed.

The only thing an ADF is good for now is listening to AM Broadcast. And they're not all that good for that

 

ADF worked just fine in the 80s but you and I were not doing the same type of flying. Of course today is different and that is the problem. People count on systems working and the day they don't chaos reigns supreme.

We have built complex systems that have very weak links. The internet, banking and navigation all rely on GPS and GPS has a Achilles heel that is ignored over time because it's been working all along. When it finally breaks it will be a hard lesson learned.

 

Agreed. Also, ADF receivers are now rarely found in newer airplanes, at least in the US. Mine does not have one.

You can say that NDB/ADF "worked just fine" but at the expense of a potentially dangerous pilot workload.

 

Awesome post and replies. I love this kind of info!

 

While "normal" navigation in small aircraft might "rely" solely on GPS, the military and the airlines do not have to completely rely on GPS for navigation.

Even if GPS completely fails or the satellites are destroyed, airlines and military will still have the Inertial reference systems which are completely self contained....no outside signals required......

GPS is also supplemented using ground based DGPS (Differential GPS) transmitters.

This can make the system independent of the satellite system but more importantly, can make the GPS NAV systems accurate to 1 or 2 centimeters.

The bottom line is, that the ADF and eventually VOR/DME and even the ILS type systems are going the way of the A-N radio range.

I'll probably leave the King KR87 in my 1947 Stinson. But I'll probably only use it to listen to the EIB Network!

 

OMG yes. It's better than FM, with the capture effect, but as you said, usally just heterodynes and buzzing and it's just a mess. ha ha! Sometimes you can pull ut some part of a call sign or what have you, but still a mess. Get a stuck mic on frequency and it's game over.

It is on 24/7 in Indianapolis, Washington, and Kansas City Centers. Every center has the capability of turning it on, and it is actually one of the systems that is tested and verified nightly in every center. There are a couple things at play. First is obviously COVID, which has put things on hold across the board, but the 2nd is that to accompany CPDLC, the scopes are being enlarged, from the 24x24 to a 42-ish inch scope. This is so that the CPDLC commands and macros and response boxes and such can be placed on the sides of the scope without losing real estate for seeing the actual planes. This requires some minor hardware redesigns to fit the scope in the same enclosure. Also, some controllers were getting very bad headaches and migraines from the new scopes, and I don't believe it was ever determined why. Not sure if it is just the sheer size and sitting that close, or if it is something else, so that slowed things down too, prior to COVID.

But it's coming!

As far as the GPS vs. IRU, WA6III would know way better than me from the aircraft side, but on our end, when there are GPS issues, the air carriers just ask about it and let us know that they lost their GPS signal, and continue about their business. Not needed. Some older aircraft (MD80, for example) would have trouble and would sometimes take some pretty wild turns if they lost GPS entirely, and of course you get the Phenom 300 (E55P) which loses its yaw damper, goes into a Dutch roll and falls out of the sky. Well...it could, if the pilots aren't ahead of it. But that's a separate issue from navigation.

Exactly! It's just a matter of time.

 

I always get a chuckle when ATC announces on a frequency "everyone check for a stuck mic!!"

Like the guy with the stuck mic is EVER going hear that message!!! HAR!!

 

LMAO!!!! I always get a good kick out of that! The only thing I would ever try to do is get people to different frequencies. Sometimes you get lucky and somebody will hear you (maybe 10-20%), but usually it just continues to be a mess.

 

Dismantling LORAN wasn't too swift either

 

We always sent a quick ACARS message to Dispatch to send out a "Check for Hot mic" message!

Or if we heard the hot mic (or a cabin announcement on primary Center freq!!) We would get on Company freq and say "Hot mic!! Hot mic!!"

That ship already sailed.....

 

As a retired Air Force communications officer and having installed ILS's in places like Kyrgyzstan and maintained VOR's and local weather sensors in places like Baghdad and ground radios in places all over the world; and having maintained ELINT systems and having directly worked with the intel community for many years; and having worked directly with C-130 pilots and air traffic controllers, I've been saying for years relying on GPS only will lead to something really bad eventually.

But there's a rising powerful force today that's forcing us to repeat history. We'll never learn. And that's what we learn from history: the only thing man learns from history is that we don't learn from history.