The Radio Stack (General Questions)

pearlygatesuk Guest


I'm hoping someone can help me. I'm flying the boeing 737-400 and the radio stack has a few buttons that I cant understand the need for.

I understand the necessiity to make the Nav 1 or Nav 2 live in order to intercept ILS. But what is the purpose of the ADF activation button (I know this is something to do with NDB's whatever they are).

There is also a DME button but as this information comes up on my cockpit window anyway with the ILS again I would ask what is the purpose of this.

And finally, what is the point of the MKR button. I'm sure there's some kind individual that will try and answer one or possibly all of these questions so thankyou in anticipation for your help.

Pearly 🙂

1 Responses

Pro Member First Officer
Barge First Officer


First of all, you should understand that all of the buttons on the radio stack are for audio signals that give morse code identifiers so you know you are tuned to the correct frequency. So there is no need to press the NAV1 button to intercept the ILS. as long as it is tuned into the NAV1 radio, it will function just fine.

So, the ADF button, just gives an audio morse id so you know you are tuned to the correct NDB.

The MKR button, when activated gives audio "warnings" when you are overhead the Outer, middle and Inner markers on an ILS approach.

The DME button will sound the same morse id as tuned into the Nav1 and Nav2 radios. If there is no morse, then the DME is not functioning or the VOR station does not have a DME readout.

Hope this helps

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