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Thread: NAV Questions

  1. #21
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    One point, to clarify Pat's last post: AM broadcast radio is, indeed, on a much lower frequency than the FM broadcast radio, but aircraft communications radios are AM, that is, Amplitude Modulation, yet are very near the FM broadcast band. So the point is that either AM or FM or several other types of modulation, can be on most any frequency.

    In other words, the modulation type and the frequency or frequency range are totally independent of each other. I'm not sure this was completely clear from Pat's excellent description of the way things are currently done.

    The transmitted signal attenuates, or decreases, at such a rate that much more than a mile or two beyond the transmitter's antenna it's so weak, receivers shouldn't be able to pick it up.
    radio probably shouldn't work
    That's why receiver sensitivity is measured in microvolts, is why reception at long distance needs a high powered transmitter, and is also why larger and/or higher antennas get better reception.

    And for the uninitiated, these are very simplified explanations.

    That's why FM is, or can be anyway, stereo and AM is only mono.
    Though I don't think it's around now, there was at one time an experiment in AM stereo -- it might have done well if FM hadn't beat them to the punch, plus it was still susceptible to all the AM interference types. I heard a little of that in the 1980s, but I didn't actually own a receiver so my experience was limited to a couple of demos. Wiki has some good info on that, BTW.

    Larry N.

    As Skylab would say:
    Remember: Aviation is NOT an exact Science!

  2. #22
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    That's why receiver sensitivity is measured in microvolts, is why reception at long distance needs a high powered transmitter, and is also why larger and/or higher antennas get better reception.
    Oh, I've done the math. Even with one of the tall, high-power TV transmission towers, the signal much more than 10-12 miles should be attenuated below the local noise. And AM doesn't do well with noise. It needs a relatively decent signal-to-noise ratio. With FM you can clip the noise, and filter the worst of it out, but not AM.

    I'm sorry if I gave the wrong impression. You are 100% correct, in that the frequency range and the modulation type aren't in any way necessarily dependent.
    Having said that, certain frequency bands lend themselves to certain applications better. Like FM needs the higher band to broadcast, since you're changing the transmitter's frequency up and down. The further you can do that, the more information it can carry on a specific channel. By the same token, if you're willing to sacrifice some of the information, you can then pack the channels closer together in a band. That's why some radios, like those on aircraft, Police, Fire, etc etc sound flat, or somewhat...bland. You're not getting the same amount of detail of the audio that you do with, say, an FM radio station.
    They spaced the FM radio stations far enough apart to be able to get some very good audio information transmission. To be able to do this, they needed a higher frequency band. You can pack AM stations very closely together, since you're changing the signal's amplitude, not it's frequency. Thus, they could use a lower band. Once again, though the drawbacks are the noise that is let through the receiver's filters, because it appears to be a part of the main signal.
    They made radar such a high frequency band because you don't want the signal to bend around things, like over mountains, into valleys, and so on. You want it to go straight there and back, to get accurate angular and distance information off it.
    Although there are stories of fighters locking onto themselves around the entire circumference of the Earth. I understand it scared them no end. Here's a plane perfectly mimicing all your maneuvers... Just a very unique circumstance, where the radar waves were bent, but not attenuated, by the atmosphere and ionosphere, and the distance was just right to appear to be another plane nearby.
    Also, different materials reflect or pass radio (radar) signals. Thus, you don't see weather (water in motion) on a radar that scans for airplanes (metal objects), and vice versa. Once they discovered the band that water absorbs, doesn't allow to pass, and doesn't reflect, but absorbs, the microwave oven was born
    Once again, first off, you need the correct band of frequencies to do all that, and you can pack the channels relatively closely together, thus two radars near one another don't interfere with each other. There are other tricks to prevent that, as well, but they're not important here. And don't even get me started on Doppler

    I'm sorry, I know I ramble a lot on this, but it's what I did for a living my entire life...
    Pat

    Had a thought...then there was the smell of something burning, and sparks, and then a big fire, and then the lights went out! I guess I better not do that again!
    Sgt, USMC, 10 years proud service, Inactive reserve now

  3. #23

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    Hi

    I'll try to stay on the OP's Topic of IFR navigation using Radio NAVAIDS .

    I respect and admire your IFR use of Radio NAVAIDS in Flight planning .
    It is a difficult topic to describe and cover well , I have collected some related Links on it , that are well worth reading , the material can be a little heavy , most will need to be read many times to digest the contents and concepts , but I think that they represent a good selection that will help you in your endeavours .

    You will find that in reading this stuff that you will feel overloaded , don't worry about it , we all feel that way when first dealing with the subject matter , it can be confusing and overwhelming .
    Just keep at it , and you will find that it slowly sinks in .

    Following are the Links ,

    https://www.recreationalflying.com/t...ion/other.html

    http://www.campbells.org/Airplanes/VOR/vor.html

    https://www.ivao.aero/training/docum...instrument.pdf

    https://www.ivao.aero/training/docum...gation_VOR.pdf

    http://www.langleyflyingschool.com/P...avigation.html

    http://wiki.flightgear.org/Radio_navigation


    https://www.ivao.aero/training/docum...gation_ADF.pdf

    Cheers
    Karol

    EDIT
    If at all possible , I would recommend that you download them .
    Place them in a folder so that you can read or refer back to them at your leisure .
    EDIT 2
    Added an ADF pdf link
    Last edited by COBS; 03-17-2018 at 06:33 AM.

  4. #24

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    How reasonable then, that the FSX Learning Center simplifies the topic, and adapts it to suit the specifics and limitations of the platform.
    e.g.
    https://www.youtube.com/watch?v=wMhEDpAvmpY

    https://www.youtube.com/results?sear...earning+center

  5. #25

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    Sorry , but you do need to study (read) , and make an effort , quick and easy won't hack it ,
    at least the OP displayed a determination to tackle the topic and a desire to learn about it ,
    he should be thoroughly commended for his attitude .
    you need at minimum the good basics .

    The OP has the choice , he can take the advice of those of us that are IFR rated in Real Life , and hence have an understanding on the subject , or ignore it .

    I still advocate that he read at least some of that material , better still all of it and tries to become very familiar with it .

    Cheers
    Karol

  6. #26

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    I would recommend flying along a flight plan, the LGC V243 VNA V362 AMG.AMG2 , the AMG2 is a STAR, or standard terminal arrival route to KJAX, this provides altitudes and class 1 navigation to the degree of accuracy required by the fat to reach destination. In the real world you would get vectors.....instead why not look at all charts for KJAX and fly a feeder route to an IAF, the IAF is usually in parentheses. From there, adhere to all altitudes and lateral navigation to let down.

    So what I have included would have you fly @5000 feet. While Navigating the 139 course to CRG at roughy 30 miles from CRG turn right to an intercept heading for the 136 to CRG. You could cross ORTAR at 2000, switch to LOC, track inbound and start down at GS intercept.....I hope that helps. Have fun!


    Sent from my iPad using Tapatalk

  7. #27

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    Quote Originally Posted by COBS View Post
    Sorry , but you do need to study (read) , and make an effort , quick and easy won't hack it ,
    at least the OP displayed a determination to tackle the topic and a desire to learn about it ,
    he should be thoroughly commended for his attitude .
    you need at minimum the good basics .

    The OP has the choice , he can take the advice of those of us that are IFR rated in Real Life , and hence have an understanding on the subject , or ignore it .

    I still advocate that he read at least some of that material , better still all of it and tries to become very familiar with it .

    Cheers
    Karol
    My advice, based on my 1100 hrs IFR Multi-engine TT, is to ignore RW advice in the ab initio phase, and concentrate on the sim's own Learning Center.

    I'm not sure why you choose to impose real life practices and procedures which are not simulated in FSX?

    K.I.S.S.

  8. #28

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    Quote Originally Posted by nuts View Post
    I would recommend flying along a flight plan, the LGC V243 VNA V362 AMG.AMG2 , the AMG2 is a STAR, or standard terminal arrival route to KJAX, this provides altitudes and class 1 navigation to the degree of accuracy required by the fat to reach destination. In the real world you would get vectors.....instead why not look at all charts for KJAX and fly a feeder route to an IAF, the IAF is usually in parentheses. From there, adhere to all altitudes and lateral navigation to let down.

    So what I have included would have you fly @5000 feet. While Navigating the 139 course to CRG at roughy 30 miles from CRG turn right to an intercept heading for the 136 to CRG. You could cross ORTAR at 2000, switch to LOC, track inbound and start down at GS intercept.....I hope that helps. Have fun!


    Sent from my iPad using Tapatalk
    Disagree: Break it down into simple elements starting with the basics of VOR navigation, then VOR and accessing the airport and runway, then ILS and Localiser, then Glideslope. Then add in GPS and switching between nav sources...

    The charts are a futile waste of time for someone who can't read a chart. That comes later, as it does in the FSX Learning Center...

  9. #29
    Join Date
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    The charts are a futile waste of time for someone who can't read a chart. That comes later, as it does in the FSX Learning Center...
    And in real life.

    The OP has the choice , he can take the advice of those of us that are IFR rated in Real Life , and hence have an understanding on the subject , or ignore it .
    Or perhaps take it from those who have taught IFR in the real world (along with teaching a few other things), and keep it simple to start with. Learning is like building blocks, start with some very basic stuff then, once that is understood, progress to a bit less simple then, once that is understood, progress to still less simple then...

    Larry N.

    As Skylab would say:
    Remember: Aviation is NOT an exact Science!

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