Tactical Radio Jammers.

SYMBOL: Radio Jamming Station Welcome to the Tactical Radio Jammers page.  Contained within this page, you will find information regarding military tactical radio jamming equipment. This is accompanied with full digital audio recordings of the various modes employed by these systems.

Note: You will require a real audio® logoPlayer® plug-in to listen to the sample audio files.


The purpose of radio jamming is to make it difficult or impossible to receive desired signals. Jamming is accomplished by transmitting a strong signal on the same frequency as that used for communications. A jamming signal me be intended to block a single frequency --- called spot jamming, or, to block a band of frequencies --- called barrage jamming.

Tactical radio jamming equipment (ECM, Electronic Counter Measures) comes in various configurations that range from ground base --- static or mobile versions, airborne versions, manpack versions and expendable versions just to name a few.

Although simple jammers have been around as long as radio transceivers have, technological advances of the past decade has thrusted forward the development of advanced and sophisticated intelligent jamming equipment.

Early jammers were but a simple transmitter keyed on to a specific frequency producing a carrier which interfered with receiving stations.

Since the advent of ECCM (Electronic Counter Counter Measures) radio equipment, the simple single carrier jammer has become ineffective. Modern day ECCM radio equipment use such techniques as Frequency Hopping and Spread Spectrum technology to circumvent the effects of ECM jamming equipment.

Modern technology has lead to the development of modern jamming equipment employed in today's tactical environment. This new breed of equipment is capable of employing such techniques as wide-band rf spectrum transmitters, and various audio tones to jam or to spoof receiving equipment and their operators. Other more sophisticated systems are comprised of frequency tracking receivers and transmitters and utilize several large directional antenna arrays that permits directional jamming and creates deep nulls towards the "friendly area" to minimize the effects of the jamming.

Most jammers feature several modes of operation and several modulation types. Operational modes range from hand keying, random keying, periodic keying, continuous keying and the more sophisticated look through mode. In the later, a special transceiver or a separate receiver/transmitter arrangement is used to selectively control the keying of the transmit circuit. The look through mode can be configured to hard key the transmitter at full power output upon detection of a received signal and periodically hard switch the transmitter rf power to off (unkey) while the receiver "looks through" to see if there is still a carrier present or, after the transmitter has hard keyed to full output power, the rf output of the transmitter is gradually slewed down to a lower level while the receiver "looks through" to detect any carrier activity on the frequency.

When a jammer is only transmitting a steady carrier, this is referred to as CW (Continuous-Wave) jamming. A CW jamming signal beats with another signal and produces a steady tone. In the case of SSB or AM signals a howl sound is produced at the receiving station. In the case of FM signals, the receiver will be desensitized, meaning that the receiver's sensitivity (ability to receive signals) will be greatly reduced.

When various types of modulations are applied to a transmitter, this is referred to as Modulated Jamming. The modulation sources can be anything from noise, laughter, singing, music, various tones etc...

Below are some modulation samples to aid in the recognition of jammer signals.

White Noise (9.6k) White Noise with Modulation (22.1k)
Tone (4.3k) Bagpipes (11.8k)
Stepped Tones (9.0k) Swept Tones (7.1k)
FSK Spoof (12.1k) Crypto Spoof (1.5k)

(The above samples were digitized using actual jamming equipment.)


jammer.jpg (32127 bytes)
Tactical Jamming and Radio Direction Finding Installation
rdf_jammer.jpg (39587 bytes)

Tactical Radio Jammers Biography
The following jamming equipment was employed in the creation of the sample digital audio files.

Racal SS2951 JAMCAT
SM-5029/U Modulation Source, Countermeasures Set
SM-5030/GL Modulation Source, Countermeasures Set
Modulation Source, Countermeasures Set AN/TLQ-15

Updated: May 06, 1998

© 1998-2014, Richard Lacroix
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