GUARD FREQUENCY

There are plenty of countries (France for example), where monitoring Guard on box 2 is a legal requirement if you are equipped that way.

If VFR, 121.5 will be the frequency they try and get you on as they send the fighters up.

My airline has an SOP that we always monitor guard (121.5) on a spare VHF to keep a listening ear out for any aircraft we can offer help to. There is a benefit to us too as if an ATC unit can’t raise us on the currently assigned frequency they will usually try 121.5 next. If you have a second VHF in your aircraft you are better off monitoring guard at a low volume level (to differentiate between transmissions between box 1 and box 2) than having the thing switched off.

121.5 VHF or double it for UHF 243……….

I know these frequencies as guard (apparantly to inform the pilot to keep it free unless in dire emergency) and as the emergency frequencies.

When flying bulldogs, which, in the RAF I think had two radios, one was always tuned to guard (in know this for sure as I heard a conversation taking place between a SAR seaking and some other party).

I think its practice in all mil aircraft to have one radio tuned to guard…..that was a while ago now tho……so maybe it is common practice across all walks of piloting life???

or maybe it should be if you have two radios??

There are two uses for guards.

I don’t think there are that many about these days as modern kit is so much more precise, the older valve and early transistor controlled radio aids tended to ‘bleed’ over other frequency’s if they were not set up correctly or went ‘off tune’.
Radio waves are just like sound in as much as co channel harmonics can result from badly aligned kit/local conditions/atmospherics

From radio theory (many years ago) a guard frequency is allocated to location where (if it were used at that location) might interact with the channels that are already in use in that area.

e.g. for a particular airfield you might see quoted
Tower: 120.25
ILS: 128.9
Radar: 124.8
Ground: 130.1
Guard: 125.5

Now, 125.5 might well be the tower frequency at your home strip but, at this example airfield above, use of 125.5 must be specifically avoided.
i.e. the guard frequency is not to be used.

More often than not these days however guard frequency’s are used at major airports to relay any activity on the emergency channel 121.5 Mhz. This is so that everyone can monitor it without actually being physically tuned to it.

Thanks alot for that.

Is it not 121.5, i heared it was for aircraft in distress, on emergency or when they cannot contact normal frequencies. Can anybody confirm this?