Emergency Frequencies
 

Aviation UHF radio straddles the spectrums (225MHz-400MHz).

Multiply 121.5 times 2....243.0. The base oscillator circuitry for carrier generation can be interchangeable, with only the divider circuitry changed between the two bands.

International Air Distress (civilian ) 121,5 Mhz
Military Air Distress 243 Mhz

However, 121,5 will be replaced soon by 406 Mhz, it seems to be started 1 feb 2009.

airman13, how are you going to make your mayday call on 406MHz?

Be careful of generalisations. I think you'll find that Emergency Locator Transmitters will have to operate on 406MHz from Feb 2009. The change is being made, in part at least, so that 121.5MHz remains clear for voice transmissions rather than suffering interference from ELT broadcasts, many of which (the vast majority, I believe) are 'set off' inadvertantly or in error.

Right On, Spitoon
 

406 MHz is an international SAR frequency, primarily for beacons...and one reason is that all the new satellites used for SAR have 406 MHz receivers. Lower transmitter power and smaller antennas.

And you would never xmit VOX on 406MHz, as aviation UHF radios only select up to 400MHz. (Of course, with an old vacuum tube monster, you could cheat it a bit out of band.)

You are confusing this with UK-registered beacons. Note that in France, you will have to have the ability to dual-transmit on 121.5 and 406 on the ELT. 121.5 remains as the frequency on the radio box.

To answer the original question, yes, 243 is technically in the VHF band, but on an aircraft it's only tunable on your so-called UHF radio, if you have one. Just one of them things.

For the "I know everything" nerds
 

VHF emergency civilian 121.5 mHz R/T
UHF emergency military 243.0 mHz R/T
MF emergency frequency 500 kHz. (it is in "the book", no idea how is used)
HF emergency frequency 2,182 kHz AM or USB R/T
UHF emergency beacons 121.5, 243 and 406 mHz.
xxx
Of interest to you - merchant marine vessels, at high seas, monitor -
HF general call frequency ship-to-ship 4,125 kHz USB (night)
HF general call frequency ship-to-ship 8,291 kHz USB (day or night)
HF general call frequency ship-to-ship 16,590 kHz USB (day)
Most ships have D/F capability on these. Can give your QDR...
xxx
:8
Happy contrails

P.S. I was an active "radio ham" in the old days...
When bored on oceanic flights, sometimes played with these HF freqs...

Hi BelArgUSA,
Nice to see you mostly on those threads wich need a piece of advice from an ''old bird of the sky'' , I think you will not be upset for this compare, but , I have a few questions.....do you think in a new era of a supersonic flights? .....do you think the airline industry will be affected by the global recession?.....will the global alliances survive in the coming years? ....thank you !

Airman13 -
xxx
Excellent idea for a subject to debate in another forum.
Suggest you do start it in "Airline, airports and routes"...
I will join in with my usual "old fart" ideas from last century.
Would be better there than under a label of "emergency frequencies".
Here, all that is suitable is mentions of Morse Code SOS.
Did did did, dah dah dah, did did did, was it...?
xxx
:D
Happy contrails