G'day

[cannon123]

Hi guys and girls,
I am B737 pilot and about once a month I have to use a DTMF mic to contact our operations staff with information. The process is pretty simple. All we do is pick an appropriate HF frequency , tune it, hold down the 5 key for 5 seconds and next thing you know they are asking which aircraft is caling them.
My question for you is what is happening? How does the tone generated make the operations staff aware that someone is calling.
I'm just interested in how it works, any info is appreciated, thanks , Cannon123

 

[OsloViking1975]

Hi guys and girls,
I am B737 pilot and about once a month I have to use a DTMF mic to contact our operations staff with information. The process is pretty simple. All we do is pick an appropriate HF frequency , tune it, hold down the 5 key for 5 seconds and the next thing you know they are asking which aircraft is caling them.
My question for you is what is happening? How does the tone generated make the operations staff aware that someone is calling.
I'm just interested in how it works, any info is appreciated, thanks , Cannon123

Click the link that is blue. It explains DTMF. http://www.genave.com/dtmf.htm

 

[cg]

My guess is that they use the DTMF mike to send a preprogrammed SELCALL to the Operations Base via HF. This alerts them that there is traffic and they can monitor the radio.
SELCAL - Wikipedia, the free encyclopedia

chris

 

[Fast1eddie]

A tone decoder built into the operator's side of the HF radio passes only DTMF tones and ignores everything else. It would seem likely that your transmitted tones would be in the receiver's memory and false tones would be rejected and not heard by the operator. I've been away from the commercial radio stuff for some time now, and can only imagine what the newer stuff is like.

Love to listen to you guys, fly safe.

 

[cannon123]

Thanks guys,
That was good info thanks.
I can only imagine what the new stuff is like too. We have 12 month old 80M$ jets with all the capabilities yet still listen to the snap crackle and pop of the HF every time we cross a waypoint and make contact using voice!
I guess it keeps the accountants happy
Thanks guys.

 

[brandon]

Sounds a lot like what I hear on the Jetstar Airways LDOC frequency.

 

[b7spectra]

I used to work HF when I was WOM (AT&T High Seas) and hated having others on the same frequency and would just blast you out! And all that QRN (Noise) on the channels!