baobab72
17th Dec 2011, 17:01
hi everyone
going over the notes i am puzzled about the working of the VOR.
Correct me if i am wrong: VOR broadcats 360 radials; each radial signal consists of an un-modulated omnidirectional carrier wave transmitted on the VHF frequency allocated to the VOR between 108.00 and 117.95MHz and constant throughout the compass rose, and of a variable signal obtained by rotating an antenna at 1800rpm 30 revolutions per second generating a subcarrier modulated at 30Hz and the phase of which varies progressively from the carrier as the signal is rotated about the station.
The onboard receiver when tuned to the VOR frequency allocated to the carrier, measures the phase difference between the carrier and the subcarrier determining on which radial the aircraft is and then feeds the data to the VOR indicator providing a pictorial view of the position of the selected radial relative to the aircraft position.
The VOR station transmits a third signal encoded on the carrier on the 1020Hz frequency containing the station identifier and any voice messages, if applicable.
In a conventional VOR or CVOR the subcarrier is modulated in amplitude while in a Doppler VOR or DVOR the subcarrier is modulated in frequency, although from a practical standpoint that doesn’t have any effect on the way the VOR is referenced to.
on an article i read that the carrier is frequency modulated at 30MHz and the variable is amplitude modulated at 30MHz and the two signals are separated by a subcarrier at 10Khz.
My question is: am i misunderstanding the article or actually the carrier is modulated in frequency - in this case the carrier has a frequency which differs from the allocated one by 30Mhz, and the variable is modulated both in frequency at 30Mhz and in amplitude, basically stretching the signal?
Is that how a CVOR works?
Also as far as i know the doppler vors to limit the site errors - cone of confusion and line of ambiguity -, allows the frequency of the signal to increase when moving towards the navaid and to decrease when flying away from it, by transmitting a 30MHZ reference signal surrounded by 50 other signals energized at 30Hz in sequence in a counter-clockwise direction:
how is that translating in an indication that the airplane is approaching the station or moving away from it? and is the doppler reference signal replacing the frequency modulated omnidirectional reference signal of the conventional vor?
is there anyway to find out the type of vor?
pretty trivial questions, just trying to understand how it all works.
many thanks
Baobab72
going over the notes i am puzzled about the working of the VOR.
Correct me if i am wrong: VOR broadcats 360 radials; each radial signal consists of an un-modulated omnidirectional carrier wave transmitted on the VHF frequency allocated to the VOR between 108.00 and 117.95MHz and constant throughout the compass rose, and of a variable signal obtained by rotating an antenna at 1800rpm 30 revolutions per second generating a subcarrier modulated at 30Hz and the phase of which varies progressively from the carrier as the signal is rotated about the station.
The onboard receiver when tuned to the VOR frequency allocated to the carrier, measures the phase difference between the carrier and the subcarrier determining on which radial the aircraft is and then feeds the data to the VOR indicator providing a pictorial view of the position of the selected radial relative to the aircraft position.
The VOR station transmits a third signal encoded on the carrier on the 1020Hz frequency containing the station identifier and any voice messages, if applicable.
In a conventional VOR or CVOR the subcarrier is modulated in amplitude while in a Doppler VOR or DVOR the subcarrier is modulated in frequency, although from a practical standpoint that doesn’t have any effect on the way the VOR is referenced to.
on an article i read that the carrier is frequency modulated at 30MHz and the variable is amplitude modulated at 30MHz and the two signals are separated by a subcarrier at 10Khz.
My question is: am i misunderstanding the article or actually the carrier is modulated in frequency - in this case the carrier has a frequency which differs from the allocated one by 30Mhz, and the variable is modulated both in frequency at 30Mhz and in amplitude, basically stretching the signal?
Is that how a CVOR works?
Also as far as i know the doppler vors to limit the site errors - cone of confusion and line of ambiguity -, allows the frequency of the signal to increase when moving towards the navaid and to decrease when flying away from it, by transmitting a 30MHZ reference signal surrounded by 50 other signals energized at 30Hz in sequence in a counter-clockwise direction:
how is that translating in an indication that the airplane is approaching the station or moving away from it? and is the doppler reference signal replacing the frequency modulated omnidirectional reference signal of the conventional vor?
is there anyway to find out the type of vor?
pretty trivial questions, just trying to understand how it all works.
many thanks
Baobab72