From The RadioReference Wiki
Revision as of 21:22, 30 November 2006 by Eorange
Where to Start?
Even if you aren't around a military base, there's still several possibilities to hear Military Communications (Milcom) traffic:
- Your local ARTCC Center uses both VHF and UHF frequencies for aircraft communications
- DOD Digital Flight Publications
- The midair refueling maps can be found here Note that it is a PDF document and about 600 pages long
- If you have one in your area, a TRACON is also another source of activity
- If you live near a major city, chances are good your local airport also uses UHF frequencies in addition to the usual civil air ones.
- Traffic in and around a Military Operations Area can often be heard; check out the Wikipedia for more information about MOAs.
- Military air-to-air and air-to-ground traffic can be heard virtually anywhere.
- Air National Guard base activity
- Nationwide NORAD activity
- Civil Air Patrol and Combat Air Patrol communications
- If you have a HF receiver, check out the Utility Monitoring article - which has lots of military related HF links
- World Aero Data
The VHF/UHF Milcom Receiver
A receiver for monitoring VHF and UHF Milcom must have the following features:
- For VHF: Coverage from 138 MHz to 143 MHz, AM mode
- For UHF: Coverage from 225 MHz to 400 MHz, AM mode
MOST milcom aircraft transmissions use AM mode. Some ground-based support for aircraft (Blue Angels) use NFM in the 138-143 MHz mode. Note that some receivers default to FM in these frequency ranges. You must have the ability to change the mode to AM.
Although these are the only hard requirements, other features are also desirable.
A receiver with a fast scan rate is necessary when scanning a large number of milcom channels. Most milcom aircraft communications are short in duration, and after a while you will be accumulating and scanning a large number of frequencies. What qualifies as a 'fast' scanner is subjective. As an example, the Uniden BC780XLT is a popular mil air scanner which can scan 100 channels per second.
Good sensitivity in the above frequency ranges is also a plus. You will be receiving milcom aircraft signals originating from hundreds of miles away, and they can be relatively weak.
See the Milcom_Receiving_Equipment for more information.
The Milcom Antenna
Many different types of antennas can be used to receive mil air communications. Discones, beams, and even wideband whips on handheld scanners can all be used. You'll have the most success by following the basic principles: use an antenna optimized for the frequency range, get the antenna up high, and minimize your loss. See the Antennas section for more details.
Scanning for Milcom Activity
See the Milcom_Web_Pages_and_Mailing_Lists for known frequencies.
Searching for Milcom Activity
Milcom frequencies are generally not published. Activity is usually found by searching the 225-380 MHz range, and then identifying what you hear on a consistent basis. So, searching this range is a good place to start.
However, searching the entire 225-380 MHz range at once is usually impractical, even for a fast scanner. A better technique is to break up this band into a number of search ranges for more efficient searching. One way to break up this band is:
- Search range 1: 225 - 275 MHz
- Search range 2: 275 - 325 MHz
- Search range 3: 325 - 380 MHz
You can further divide these chunks into smaller ranges to suit your receiver's search abilities. Also, milcom aircraft communications use a 25 kHz step size. This is important; setting your step size to 25 kHz allows for faster searching and reduces the chance you'll miss a comm (smaller step sizes means longer searches).
The 380 - 400 MHz Range
The military uses this range for APCO-25 trunked systems.