ADF V+ Design

feature author: Paul Halliday

This design is very similar to the NAV/DME design. Again I’ve split it up into two sections: Pilot and CoPilot. Let’s discuss the Pilots’s section first.

There are nine inputs from the host and three players. The Pilot Audio ADF input is a switch on the n the cockpit’s audio panel that allow the pilot to selectively listen to the ADF radio. This switch is combined with any signal going to a player’s volume pin. The ADF’s master volume input is also combined with any signal going to a player’s volume pin. There are four inputs grouped under the label ADF 1 Ident Letters. These inputs represent the four-character ADF station identifier. They are fed into an ADF Keyer object, which generates the Morse Code pulses for the Ident Tone player.

The ADF 1 Freq Diff and ADF 1 BFO On inputs are used to model a Beat Frequency Oscillator. This has to do with older NDB transmitters use keyed carrier waves. Very few of these are left in existence, and most modern-day ADF receivers have phased-locked tuning, eliminating the need for using these controls to properly tune the ADF radio. The Beech 1900D didn’t need to use this capability, but I left it in anyway because it shows how robust this model is. 

As was the case with the NAV/DME design, all of the players in the ADF design have fixed constants that feed the frequency, balance, and enable pins. Again, there is no need to dynamically change these attributes of the players.

Figure 42.  ADF Design (Pilot)

Figure 43.  ADF Design (CoPilot)

Like a VOR transmitter, the ADF generates tone pulses of 1020Hz.