T400 Quick Start Instructions

ADEPT T400AM AND T400CW TRANSMITTERS

Instructions

Quick Start, Short Form

Insert the battery into the battery holder with the negative end toward the spring. Turn on your receiver, and tune it to the approximate frequency printed on the T400 transmitter. The mode of the receiver must be AM to receive a T400AM transmitter, and the mode must be CW to receive a T400CW transmitter. Actually, you can find and hear the signal in any mode, such as FM, but efficiency will be poor.

Using the T400AM Transmitter

Your receiver must be in AM mode, and the frequency should be set to the approximate frequency as indicated on the T400AM transmitter. You should immediately hear the beeping signal. The Transmitter turns on every 1.3 seconds for 50 milliseconds, and the carrier pulses are amplitude modulated with a 1,000 Hz tone frequency. (With a T400CW the 50 millisecond carrier pulses are not modulated.)

Normally, in AM mode, the frequency tuning increment should be 5 kHz—the frequency changes 5 kHz (up or down) with each click. Momentarily remove the antenna from the receiver to cut down the signal strength at close range. Tune up or down to find the precise frequency of the transmitter. From the true center frequency, tune up or down two or three clicks and note how the signal level drops off. NOTE: this trick can be used with an AM receiver while tracking, to attenuate the signal strength when close to the transmitter.

When the transmitter is near metal objects such as rocket launch rods, the frequency may change a little. With an AM receiver with its wide bandwidth, the effect is minimal. However, you should become familiar with the frequency shift effects, when the transmitter is away from objects, such as when hanging on a string, and then when near a launch rod, and also when the transmitter is on the ground.

Tracking the AM Transmitter

Connect your receiver to the directional antenna with a short cable. Use a BNC to SMA adapter if necessary. To gain some experience with your directional antenna, place the transmitter on a pole or on the ground, and take a hike. Listen to the transmitter as you back away, a few hundred yards, or half a mile or more. Touch up the receiver tuning if necessary as the signal gets weaker. Aim the antenna toward the transmitter. Slowly twist the antenna for the loudest signal, to find the proper orientation (signal polarization). Slowly swing the antenna to both sides and notice how the level drops off. This is how tracking works—aim the antenna back and forth to determine the direction of the loudest beeps.

You will get the best results when the incoming signal is low, to very low. Attenuation of the signal is absolutely necessary as you get close to the transmitter. Some receivers have a one or two level built-in attenuator. With an AM receiver, you can detune a few clicks, to attenuate the signal. You can do this at first, but the best solution is to use an attenuation device between the antenna and the receiver. Keep the incoming signal at a low level, the lower the better. Then when you turn the directional antenna away from the signal, the volume level of the signal drops off dramatically.

Using the T400CW Transmitter

Your receiver must be capable of receiving CW. Put it into CW mode, and set the frequency to the approximate frequency as indicated on the T400CW transmitter. You should immediately hear the presence of the signal, but you may not be tuned close enough to hear the actual beeping signal. Remember, a CW receiver mixes an internal beat frequency oscillator with the incoming signal to create a beat frequency that is in the audio frequency range. The Transmitter turns on every 1.3 seconds for 50 milliseconds. The 50 millisecond carrier pulses are not modulated.

In CW mode, once you can hear the signal, you should change the frequency tuning increment to the minimum the receiver allows, 100 Hz, or even less. The frequency changes 100 Hz, or less (up or down) with each click. Momentarily remove the antenna from the receiver to cut down the signal strength at close range. Tune up or down to find the precise frequency of the transmitter. Tune until you can hear the actual beeps. Adjust the tuning until the beep tones are pleasing to you. Most hams prefer tones from about 600 Hz to a little over 1 kHz.

When the transmitter is near metal objects such as rocket launch rods, the frequency will change. With an AM receiver with its wide bandwidth, the effect is minimal. However, with CW the frequency shift effects are greater. You should become familiar with the frequency shift effects when the transmitter is away from objects, such as when hanging on a string, and then when near a launch rod, and also when the transmitter is on the ground. Be ready to retune when necessary.

Tracking the CW Transmitter

Connect your receiver to the directional antenna with a short cable. Use a BNC to SMA adapter if necessary. To gain some experience with your directional antenna, place the transmitter on a pole or on the ground, and take a hike. Listen to the transmitter as you back away, a few hundred yards, or half a mile or more. Aim the antenna toward the transmitter. Slowly twist the antenna for the loudest signal, to find the proper orientation (signal polarization). Slowly swing the antenna to both sides and notice how the level drops off. This is how tracking works—aim the antenna back and forth to determine the direction of the loudest beeps.

You will get the best results when the incoming signal is low, to very low. Attenuation of the signal is absolutely necessary as you get close to the transmitter. Some receivers have a one or two level built-in attenuator. Use it. Eventually you will realize that the best solution is to use an additional attenuation device between the antenna and the receiver. Keep the incoming signal at a low level, the lower the better. Then when you turn the directional antenna away from the signal, the volume level of the signal drops off dramatically.