Military radio tones

[Bigears]

Whats the purpose of these tones? (I know about the SARBE thanks!!).
Examples are only a tone transmited from a formation, or a tone + voice transmitted from a singleton.
I'm sure its a simple answer..........

[FE Hoppy]

some training a/c have a tone when the gear is down as a reminder for atc when in the circuit.

[HEATHROW DIRECTOR]

I'm not wholly sure I understand what you mean by the transmission of tones. Do you mean a continuous noise or the "roger bleep" thing which CBers and NASA use to produce a quick burst at the end of a a transmission? If it's a continuous tone it might be to do with the a/c electronics. Commercial a/c R/T has improved greatly over the years but when I first started at Heathrow back in the early 70s one could recognise many a/c types simply from the r/t sound. BAC 1-11s always had a tone behind the voice but it was some sort of inverter whine rather than a deliberately trasmitted tone.

[ 16 January 2002: Message edited by: HEATHROW DIRECTOR ]</p>

[spekesoftly]

Just wondering if Bigears may be refering to the tones that some military aircraft can transmit in response to ATC interrogation using the 'speechless code'. If a pilot has an unserviceable microphone, he can reply to ATC questions with one tone for "yes", two for "no", three for "say again" etc.

FE Hoppy is, I believe, refering to the 'Ultrasonic Undercarriage Position Indicator'. It was certainly fitted to the RAF Jet Provost, maybe others.

There must be a PPRuNer who is a lot more up to date than me on these things! Whipping Boy's SATCO are you there? <img src="wink.gif" border="0">

Heathrow Director, have you done your last night shift yet? If so, wishing you a well deserved and happy retirement.

[ 16 January 2002: Message edited by: spekesoftly ]</p>

[Bearintheair]

I work in the Police/HEMS world and sub audible tones are used on some of our Police/HEMS channels. The tone is automatically transmitted at the start of a transmission from the aircraft or a ground unit. Its purpose is to open up the receiver at the control room for our transmission. Transmissions from other sources without the tone will not open up the receiver and will not interfere with our operational traffic.
Our police force applied tones to their force VHF net in order to cut out interefernce from french taxi drivers which broke through given certain atmospheric conditions.

[Bigears]

Thanks for the replies- all very interesting!
I think that FE Hoppy and spekesoftly have the answer;
The aircraft that I have heard use this tone (quite loud, about half a second duration) have been (I believe) the Red Arrows, a Mirage and, a few days ago, which sparked the question, some Harriers. If the Mirage was a 2seater (possible as it was at an airshow), and the Harriers (operating at night in 'the sticks') were 2seaters practicing field operations, then it all ties in.
Anyone else care to comment?
BTW, Happy Retirement, Heathrow Director- you'll no doubt have directed me (as a pax!) a few times.

[HEATHROW DIRECTOR]

Spekesoftly... I'm still interested in the tones, especially having experience of speechless QGHs in another life. That procedure is usually used by pilots with microphone problems and all one hears is a carrier wave. Do military radios now have the capability to transmit tones when the mic is u/s.

Thanks to those who made kind comments about my retirement.. Last two night duties this weekend and then on part time work for a few months (ie no more nights!) before hanging up my hat.

[spekesoftly]

Heathrow Director .... As you rightly say, the 'speechless code' can be used with carrier wave only transmission, for QGH or radar recovery. In theory it could be used by civilian as well as military pilots, but I suggest that it is/was more widely taught in the military.

Some military aircraft, in addition to the normal R/T transmit button, were, if I remember correctly, fitted with a separate 'Tone TX button' that could also be used in the circumstances described. As best I can recall (long time ago now!) - the tones were much easier to discern than a carrier wave, especially on a busy frequency.

[ 17 January 2002: Message edited by: spekesoftly ]</p>

[HEATHROW DIRECTOR]

Spekesofly.. Gottit.. Thanks very much for the info.