# How does a TACAN signal change with bearing from the station?

In the TACAN system , how does a change in bearing , would translate to a change in the time (or frequency) domain.

I'll try to elaborate:

I'm aware , of the TACAN operation in general.

let's say that I'm 270 degrees (referance to north) and 180 degrees (referance to north) , how would this change reflect on a Scope or on a spectrum analyzer if at all (of course I mean in the analog signal).

• Take a look here for what scope traces would look like at various times. I am not going to copy the page. opticfox.com/2a4x2/tacan-fun.htm – CrossRoads Jun 24 '19 at 11:56
• hello Cross , thank you for replying , I have went over that website several times , unfortunately, I could not see the change on scope from bearing differences, It explains it work in general , I'll try to clarify my question , what I'm trying to get is a variable that I can track which could lead me to calculating the bearing information may it be the pulse amplitude or envelope frequency. – Alex Rudyak Jul 1 '19 at 6:39

Change in bearing doesn't change frequency. The ground station always transmits pulses on a single assigned frequency. The illustrations in the link from @CrossRoads only show what would be seen by a receiver at 000 magnetic. For other bearings the whole envelope shifts while the reference bursts stay still. The antenna illustration shows reflectors on spinning drums that create an envelope whose phase difference from the reference bursts depends on bearing. My markup of the diagrasms in the link (MRBs are blue):

A TACAN or VOR station actually transmits two signals:

• a reference signal whose phase shift is independent of azimuth angle
• a signal that is phase shifted, where phase shift (0-360°) equals the azimth angle

At the receiver side the phase difference of both signals is determined. The phase difference equals the bearing.

There are various ways of generating signals whose phase shift equals the azimuth angle:

e.g. in AM: by mechanically rotating a directional antenna

e.g. in FM: rapidly switching from one antenna to the next one among a set of antennas placed on a circle.