Adept Instruments - Tracking, RDF, and Fox Hunting Transmitters

The T400AM/T400CW Transmitter, originally designed as a Model Rocket Tracking Transmitter, was first offered in 1999, and sold under the business name Adept Rocketry. The T400AM transmits AM burst tone signals. The T400CW transmits keyed on and off CW signals. Designed as Tracking Transmitters, they also serve well for "Fox Hunting."

Tracking and RDF Transmitters

Fox Hunting Transmitters

The transmitters from Adept Instruments operate on a frequency of 433.92 MHz. They can be programmed to operate in either AM mode or CW mode (no FM Mode). The first transmitters we offered were on the two-meter Amateur Radio band. They were larger and heavier than we preferred, and we found the directional tracking antennas to be large and bulky. Once we chose to use 433.92 MHz we were able to make the transmitters much smaller and lighter, mainly because crystals and other components for this frequency became readily available. Also, at this frequency the directional tracking antennas are quite small and easy to maneuver, and they cost less.

Why just one frequency? The particular frequency of 433.92 MHz is used all over the world for many different things, such as for remote temperature sensors in small consumer weather stations. The power output from these devices is usually in microwatts, and the range is very limited. A license is not required. In a typical neighborhood you can occasionally hear these signals, but they are never a problem.

Because of these devices and other uses, the frequency of 433.92 MHz has been rendered useless for most ham radio operating activities such as low level signal work. So we decided to use the frequency for miscellaneous tracking, radio direction finding, and fox hunting. It turned out to be an ideal frequency for our purposes.

Generally there is seldom a need for more than one transmitter to be in operation at the same time at the same location. However, when this will be the case, Adept has a solution. By special order, the AM tone modulation (beeps) of an AM transmitter can have one of up to six different sounding patterns. They are BEEP, BOOP, BEEP BEEP, BOOP BOOP, BEEP BOOP, and BOOP BEEP. You can literally track several different AM transmitters at the same time when each has a different modulated sound. Sorry, but this will not work with CW mode.

Adept transmitters have been tested at a distance of 15 miles line-of-sight, and the signals were still receivable and very useable, in both the AM and CW modes. The expected range when used at high altitudes is considerably greater. Theory predicts that they should be more efficient in CW mode. However, during testing we found no perceivable difference. So most transmitters we deliver are used in AM mode. Many hams already have the necessary receiver for these transmitters—most multiband HTs include a wide band receiver with the ability to receive AM at 433.92 MHz.


When ordering an Adept transmitter, Adept requires proof of your Amateur Radio License. Your call sign is sufficient. When operating, the transmitter will periodically identify by sending your call sign in Morse Code.

The Adept T400 Transmitter is now available in various forms. They operate in either AM Mode, or in CW Mode. Most of them, including the original T400AM/T400CW are user programmable for either AM or CW mode, and for a message and/or call sign. The transmit frequency is 433.92 MHz, and at this frequency the directional tracking antennas are quite small as compared to antennas for the 2 meter Amateur Radio band. Adept does not offer transmitters for the 2 meter Ham band.
 
 
www.adepinstruments.com       08/11/16

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