N4JRI's Radio Pages: Aircraft Monitoring

Air Monitoring Pitfalls to Avoid


Too Many Air Traffic Frequencies - If you are plane-watching at a busy airport, beware of all the approach, departure and clearance delivery frequencies that are available to you. Many of these may be simulcast, and can hang up your scanner on a frequency on which the aircraft will not answer. I recommend that you start off listening only to the Tower and Ground Control. Almost all aircraft visible to you will be on these frequencies and there will be a lot of chatter. At a busy airport, it's hard to follow more than one aircraft throught he system at a time.

The opposite is true, though, when monitoring the military. If you are out of range from ATC ground stations, you can tune in the UHF (225-400 MHz) ATC frequencies and they will quietly scan until an aircraft opens your squelch.

Beware of Scan Delay - Scan delay is generally a dangerous thing in air monitoring, because ground stations often simulcast on several frequencies. If you get hung up on the wrong one, you'll never hear the aircraft reply. Each air traffic control frequency is simulcast on a UHF frequency. This probably means that Tower and Ground have two frequencies each. If the Tower and Ground positions begin to simulcast, that's four different frequencies to deal with. Add Clearance to this, and you have at least six. The same problems arise with Approach and Departure frequencies. Do yourself a favor. Avoid using your scan delay feature at airports, or within range of ground stations.

Air Traffic Control Ground Stations - Again, each of these channels is simulcast on VHF and UHF, and individual positions my simulcast if they are combined during periods of slow traffic. This is particularly true when listening to the military. You may think you've found the motherlode in the 225-400 band, but careful listening to an Air Traffic Control ground station will generally reveal that most of transmissions are civilian in nature.

Full-Band Searching - Even the VHF air band is a big place to search. Transmissions are very brief, so don't search more than your scanner can cover in 5 seconds. Don't just search 108-137. Think about what you're looking for:

Searching 225-400 MHz - This band is so huge that little is to be gained by searching it all at one time. The best approach to the Military is memory scanning of local Air Traffic Control Frequencies, and other commonly used frequencies. From here, you'll aircraft changing channels and your list will grow accordingly.

Searching 30-88 MHz FM - Again, much too large a band to scan in its entirety. While the radios can technically use any frequency in this range, you are fairly safe in skipping over civilian allocations. The vast majority of military traffic is in the federal segments at 34, 36, 38, 40, 41, 46 and 49 MHz. Very little is reported above 66 MHz, although I know of two National Guard helicopter units who operate within the 6 meter ham band at 50-54 MHz.


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