13

There's no specific reason why the lower frequencies are used for towers, but it's not a coincidence that they are grouped together (mostly, there are tower frequencies that are not at the lower end.) Spectrum management is a complex effort to make maximum use of the fixed amount of frequencies available for use. In the US this falls under the FAA Spectrum ...


9

Use of a metering controller and frequency at an airport is one strategy used to prevent congestion on ramps and taxiways. When ready for push back from the gate, pilots call metering. The metering controller will typically either give them permission to push with a ground frequency to call when ready for taxi, or they will tell them to monitor a particular ...


7

Additionally, there will be more aircraft interrogating (on 1030MHz) and responding to interrogations on 1090MHz for transponder based systems (TCAS, SSR). Actually, no. More Mode S (vs Mode A/C) aircraft means TCAS can use Selective interrogation instead of All-Call interrogation, which will reduce congestion from unnecessary replies. Also, newer TCAS ...


7

In VOR early days, the 40s, the stable phase locked loop frequency generator was not available. A common frequency reference was the very stable public AC power grid frequency. The angular velocity of a synchronous motor is locked on the power source frequency, such motor can be used to actuate a variable resistor or capacitor to generate a stable wave which ...


6

That division is applicable only when the parallels (4's or 22's) are in use, which is the preferential system (see title of chart). As for rwy 12/30, from the eAIP (PDF; link may die; homepage): Between 6 AM and 11 PM local: RWY 12 and RWY 30 may be used when one or both of the preferential runways cannot be used (...) Between 11 PM and 6 AM local: ...


6

There are sector maps available, and each facility updates them periodically. They are published. My understanding is that sectors are joined and separated frequently, even based on the minute to minute workload. (I have a set of charts showing High, Low Center and tracon sectors. I haven't found a public source for those charts yet. Here is a set of maps,...


6

From the document referenced by mongo, Frequencies (MHz): 121.425 - 121.475Use: Band Protection for 121.5 Frequencies (MHz): 121.525 - 121.575Use: Band Protection for 121.5 It seems that these frequencies exist only to be silent space around Guard/121.5. No one should transmit on them, and you should probably hear total silence there. I think these ...


5

The example KFCM to KRNH starts under the Class B shelf, in this case you check KFCM's chart supplement, and it says, "MINNEAPOLIS APP/DEP CON 134.7": Which also agrees with the sectional (shown below). Zoom out in the sectional, and you'll note different frequencies to the NW and NE of the Class B, so if you're transitioning through, the ...


5

You might want to check out this list of assigned frequencies. These look like good bets. 136.100 Reserved for future unicom or automatic weather observation stations 122.975 Unicom (high altitude)/U.S. Forest Service air operations 123.125 U.S. Air Force NAVAID flight check/NASA T-38 Interplane Nationwide


4

in that frequency range (118-137MHz) you are correct, the percentage change in frequency from the bottom to the top of the range is small, so there will be no significant change in propagation characteristics, range, data rate, etc. going from 118 to 137. In addition, the same radio antenna can be effectively used across the whole frequency range, simply by ...


4

There are published instrument approach procedures for all airports served by an instrument approach. These are commonly referred to as Approach Plates. (In paper form). Your local pilot shop should have them, or you can order online. Just look in the section for the airport you are going to and all the available approaches will be there. Browse to the ...


4

The frequencies are chosen to allow the system to produce a localizer and glideslope 'beam' that provides proportional guidance that can adequately guide an aircraft on the approach. Read through this Question and Answer. As you can see in the description of the beam-forming, the width of the antenna array and the choice of the modulation signals (90 ...


3

The FCC publishes the frequency assignments for aeronautical radio usage (Part 87). You may wish to "listen" anywhere, but technically one should be monitoring guard when a receiver is available. https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC90-50D.pdf https://www.gpo.gov/fdsys/pkg/CFR-2016-title47-vol5/xml/CFR-2016-title47-vol5-sec87-173....


3

I'd try 121.1 to 121.4. I am not aware of them having been assigned for routine use. There's no guarantee that an unassigned frequency won't be in use by someone, authorized or not. Use of frequencies between 121 and 122 are typically limited to 'low power' or other restricted applications to avoid adjacent channel interference with Guard. This is why ...


3

May not have been an explicit consideration, but the bottom of the band is pretty close to Band II FM broadcast radio. 118MHz could interfere with 96.6MHz transmissions, the difference between them being 21,4 MHz, twice the usual 10.7MHz IF (intermediate frequency) This is known as the "image frequency". It's only problematic with a "high side&...


3

I have found something that will work. It is not pretty and I swear I can still smell the punch cards that produced the text files, but here it is: https://www.faa.gov/air_traffic/flight_info/aeronav/aero_data/NASR_Subscription It is free, it appears to be updated by the FAA, (I verified it has the current frequency for my local VOR that I know changed 2 ...


3

An AC motor in the USA will turn at 60 RPM and 90 is 3/2 and 150 is 5/2 of 60. Both can be generated using a simple gear drive which would reduce the costs during development. Similarly there are circuits to multiply or divide a driving frequency by whole numbers, with 60 hertz readily obtained. Simple gear ratios could convert 50 hertz used elsewhere. 90 ...


2

In order to see metering in action, use http://liveatc.net and monitor the metering freq during bad weather like falling snow, typically at a northern airport like KMSP. Departure ATIS ( not arrival ATIS) will direct all flights to use the metering freq and then the metering freq asks if the flight needs deice. If it does, then metering directs the flight to ...


1

A good place to start getting the info you seek is The Airport/Facilities Directory and NOTAMS give you the actual availability on a day-to-day basis. Some RWYs have a Localiser BackCourse approach - LOC BC RWXX; If RW 9 has an ILS, the same Localizer has a Back Course (BC), that lies on RW 27 Approach centerline. Every Localizer has a back course. Obviously ...


1

That information can be found on FAA.gov You can use the FAA's search tool rather than manually look in a copy of the chart supplement. However, updated PDF copies of all of the chart supplements are hosted by the FAA here.


1

When ILS was developed, they actually used rotating capacitive plates with lobes. The 90 had 3 lobes and the 150 had 5. Easy way to modulate the RF with the phases locked. The depth of modulation was adjusted with a fixed plate with a variable gap between it and the rotating plate.


1

With respect to the radar frequency drift, I am afraid you are asking an impossible question, the interrogation frequency is continuously auto monitored, any drift tendance is electronically prevented. However should this occurs, the aircraft transponder has a sharp filter limited just to light Doppler effect, beyond that the transponder will not answer to ...


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