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IO540
5th Jun 2007, 14:04
What happens if you carry two 121.50/406MHz units and, in an emergency, activate both of them?

S-Works
5th Jun 2007, 14:20
Twice the chance of being found!!!

IO540
5th Jun 2007, 14:23
Not if they interfere, which is why I asked. I will make some enquiries.

Three Yellows
7th Jun 2007, 19:30
IO540

What's the answer?

Surely you'd be okay if one was round your neck and the other one at the bottom of the sea?

IO540
7th Jun 2007, 20:59
Apparently, it's OK, because commercial boats have two or more anyway.

It probably relies on random variations in the crystals. If you had two transmitting on exactly the same frequency, from the same spot, I don't see how you could modulate any information (e.g. the GPS position) on to the carrier. The data rate must be low enough to keep the sidebands close enough to the carrier, so that two of them don't interfere.

Three Yellows
8th Jun 2007, 08:35
That's useful to know....

.... if we go anywhere near water my mate insists on having one round his neck, wearing his lifejacket, clutching the dingy, the aircraft has a properly installed/approved one ..... and we've got a twin!!

denhamflyer
8th Jun 2007, 10:13
Remember the beacon is not a continuous transmission and "chirps" every so often so in probability they will not collide or if they do then they will slowly drift apart and then two "chirps" will be heard. This method saves power and also leaves the frequencies available for multiple use.