VHF/UHF Military Monitoring
This page is an introduction for those new to the world of VHF and UHF military monitoring, as well as for folks more seasoned in the hobby.
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
- 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 HF Military Communications article
- World Aero Data
The VHF/UHF Milcom Receiver
A receiver for monitoring VHF and UHF Milcom must cover, at a minimum, the 225-400 and 138-144 mhz ranges. Mil flights sometimes also use the civil air band (118-136 mhz) range. With the exception of the civil air band (where AM mode is the norm) and the VHF Low/162/406 Mhz bands (FM), either AM or FM mode transmissions may be heard in these ranges. Starting with the 2005 airshow season, monitors reported hearing Blue Angels ground support units using NFM mode in the 138-144 Mhz range. Clearly the ability to change mode independent of the frequency being received is very important.
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 page for more information about receivers, scanners, antennas, and filters. Also, reviews and user comments from EHam are linked here, along with Wiki pages devoted to many different models.
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.
Scanning for Milcom Activity
- See the Milcom Web Pages and Mailing Lists page for known frequencies. This page gives you a great many possible sources of information. Don't forget to look at the RadioReference Databases first!
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 interval. 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).
Logging your Milcom Hits
Before long, you will accumulate a large number of milcom frequencies. However, not all of these frequencies will be active all the time, especially if you're not located near a region with a high amount of milcom activity. For example, NORAD frequencies may only be active during certain exercises, as opposed to aerial refueling which happens on a more regular basis.
Logging your milcom activity can help you identify the frequencies that are more common for your area. You can do this if you have software that supports frequency logging for your receiver. Log the milcom hits on your programmed frequencies on a daily basis, over a period of a week or 2 (or longer). After a while, you'll accumulate a set of "primary" milcom frequencies for your area. The same technique can be applied to searching as well.
Along with logging, recording activity is a convienient way of capturing what you hear for later review and retrieval. We have several packages compatible with many different scanners in the Recording Software and Tips and Radio Control Software articles for software and various hints and problems with feeding your scanner audio to your PC.
You should be aware that GRE/RS scanners cannot scan and log or record - it's simply not in the firmware to allow for this function. The lone exception is the Pro-2052, which has Uniden firmware and can be computer controlled.
The 380 - 400 MHz Range
While aero operations and other modes can be heard here, various military and federal users have established APCO-25 trunked systems in this band.
When fully operational, some of these systems will not be monitorable by any scanner. However, several systems have come on line that can be trunktracked. Currently, Uniden's BCD396T, BCD996T and GRE's PSR-500, PSR-600, or Radio Shack's Pro-106, Pro-197 scanners can trunktrack these systems. Other digital trunktrackers can listen to such systems in a conventional mode.
If you are using a Pro-96, Pro-2096, Pro-106 or a Pro-197 scanner from Radio Shack or a PSR-500 or PSR-600 from GRE, and you hear a 9600 bps control channel in this range, a utility known as Pro96Com (a Trunker like utility) can be used to monitor activity found here. However it should be noted that neither the Pro-96 or Pro-2096 can receive in this range without being opened up with Starrsoft's Win96 program. As neither of these 2 scanners were originally designed to receive in this range, this procedure may not work well - one Pro-96 may receive it, another Pro-96 won't.
Satellite Communications (SATCOM)
Military communications over satellites can occasionally be heard. Note that just about all U.S. military SATCOM voice transmissions are encrypted. Occasionally you can hear short comms in the clear, like voice testing, but this is infrequent. You can also hear telemetry and other constant data streams. More often, you can hear what sounds like casual conversations in languages other than English, but the reason for this is somewhat unclear.
A receiver for monitoring SATCOM must satisfy this requirement:
- Coverage from 240 MHz to 270 MHz, NFM mode
Just like VHF/UHF Milcom, SATCOM uses an interval of 25 kHz. Optimal setups for receiving SATCOM are unique, involving hi gain antennas designed for correct polarization of the SATCOM signal.
It is possible to hear SATCOM with nothing more than a handheld and a wideband whip. This technique involves going outside (SATCOM signals are relatively weak), searching the SATCOM frequency range, and experimenting with orienting your whip from vertical to horizontal. Listen carefully for carriers and periodic data bursts, and of course the voice traffic mentioned above.
- See the SATCOM page for more information about amateur and military satellites, along with tips for hearing - and maybe working - the International Space Station.
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