How does V.O.R REALLY work?

[2fst4u]

Lately in Level 3 physics (year 13 or form 7 for you oldies out there) we have been learning about waves, phase diagrams and constructive/destructive interferrence. I fully understand how two identical radio signals in slightly different positions can make waves that double in amplitude in many directions, and completley cancel each other out in just as many positions. But I just cannot figure out how VOR works. I know there is a signal that is emmited in all directions at regular intervals, and that there is a signal electronically directed (from what i understand) in a complete circle... but how does this create constructive and destructive interfference? and how does this interferrence translate into a radial that can be dialled up in the cockpit?

I know this topic may be slightly over-the-head of many people but this is really doing my head in. And if someone could fill me in on the gory details of this confusing subject I would be very greatful.

BTW, yes I have googled this topic, exchanging keywords for keywords and i have tried to find proper explainations but none are satisfactory, all telling me that the OBI 'calculates' the time taken for the VOR signal to spin which I know is not correct.

[ZK-KAG]

Hi There,

The VOR principles in very very simple terms has two signals emmited from the station. The first signal is emmited in 1 degree increments for a full 360 degrees. A second signal is emmited at each degree, however it is progressively as it goes around the 360, 1 degree out of phase. So if you want the 315 radial, the phase difference of the second signal is 315 degrees out and so on.

Hope this helps

[bennz]

Have a look at this document.
It might look a bit complex at first but explains how VOR works on VFH band and frequencies.

www.casa.gov.au/pilots/download/VOR.pdf


P.S : make sure you don't confuse VOR with ADF

[ardypilot]

QUOTE

I know this topic may be slightly over-the-head of many people but this is really doing my head in.[/quote]
Don't worry, it's a question that takes 3 weeks worth of explanation in IFR classes to understand! Although KAG has simplified it nicely

[2fst4u]

haha, nice explaination. what about the OBI? how does the phase difference translate into needle movement?

[ZK-KAG]

QUOTE (2fst4u @ Jul 30 2009, 04:09 PM) <{POST_SNAPBACK}>

haha, nice explaination. what about the OBI? how does the phase difference translate into needle movement?

Not gonna get technical here, but the OBI/HSI/RMI measures this phase difference and works out where it is in relation to the radials. The instruments then show how many degrees you are off course etc.

QUOTE (Trolly @ Jul 30 2009, 02:03 PM) <{POST_SNAPBACK}>

Don't worry, it's a question that takes 3 weeks worth of explanation in IFR classes to understand! Although KAG has simplified it nicely

Only at AFS eh Andrew hehehe *takes cover!*

Im a trainee instructor, keeping it simple is the name of the game

[WasFlightOps]

Not sure how a physician is going to help you....a physicist on the other hand....

[2fst4u]

someone needs to prescribe me some meds. 'cause the concept is painful to understand

nah thanks for the help guys. I like knowing how things work, rather than giving up on them

[ardypilot]

QUOTE (ZK-KAG @ Jul 30 2009, 10:06 PM) <{POST_SNAPBACK}>

Only at AFS eh Andrew hehehe *takes cover!*

Im a trainee instructor, keeping it simple is the name of the game

Trust a Massey student to come up with such a snappy comeback

Hows things going down there? Are you going for your C Cat?

[ZK-KAG]

Yeah you and I both know which place is superior...

Yep got my test in 2 weeks eeeek! Then after that hopefully a DA-40 type rating and a job!