|T400P Transmitter, Instructions|
|Turn on your receiver, and set the frequency to 433.92 MHz. The mode of the receiver must
be AM to receive a T400P programmed in AM mode, and the mode must be CW (or SSB) to receive
a T400P programmed in CW mode. Actually, you can hear the signal in any mode, such as FM,
but efficiency will be poor. Connect the T400P to a 9V battery. The transmitter is silent
for the first ten seconds. Then it sends out the internally programmed information such as a
call sign. During the ten second silent period, the T400P may be reprogrammed with new
information, such as a different call sign or other string of characters, and the mode can
be set to AM or CW. See Programming the T400P Transmitters below.
Using the T400P Programmed in AM Mode
Your receiver must be in AM mode, and the frequency should be set to 433.92 MHz. You should 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 T400P in CW mode 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.
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 move 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 T400P Programmed in CW Mode
Your receiver must be capable of receiving CW. Put it into CW mode, and set the frequency to 433.92 MHz. 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 1 KHz.
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 move 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.
Get Familiar With Your Transmitter
With your receiver, you should be able to quickly find the transmitted signal near 433.92 MHz. If the receiver includes an attenuator function, then turn on the attenuator, to maximum if there is more than one setting level. Watch the tuning indicator and tune the frequency to maximum indication - which should totally overload the front end of the receiver. Now remove the antenna from the receiver. You should still be able to hear the transmitter just fine. With the much lower signal you should be able to tune the receiver to the exact frequency.
General Information and Specifications
The T400P transmits a 50 mS beep every 1.3 seconds. To receive the signal, you need a receiver that can be tuned to 433.92 MHz, and a directional antenna. To pick up a CW signal from the T400P, you need a special communications receiver that can receive CW. Most people use the T400P in AM mode, since AM mode is the easiest to use, and AM capable receivers are available at lower cost. Also, numerous dual or triple band ham radio handy talkies are available in the $130 to $200 range, and many of these handy talkies have a wide-band receiver that can be put into AM mode while tuned to 433.92 MHz.
The lowest cost radio tracking system would be a T400P in AM mode, a receiver that can be tuned to around 433.92 MHz and put into AM mode, a directional antenna such as the ANT440-3, a 3-foot BNC coax cable to connect the antenna to the receiver, and if needed, an adapter connecter to adapt the receiver's SMA connector to the BNC cable. For most users the AM mode will serve just fine.
Later on you may wish to add an attenuator between the directional antenna and the receiver. This will allow you to keep the incoming signal at a low level for better directional efficiency. Often with AM, an attenuator is not necessary at first, because you can just detune the receiver a little to attenuate the signal. Later you may wish to upgrade to a 5-element, or a 7-element antenna for more directional gain.
Remember, you must have an Amateur Radio (Ham Radio) license to legally operate the transmitter. Adept requires proof (call sign) of your license.
The T400P transmitter has a power output of 8 mW. It can be heard over 50 miles in the air, and a mile or so on the ground. In AM mode it transmits a 1 kHz modulated 50 mS pulse (beep) every 1.3 seconds. The AM receiver demodulates the beeps from the signal and sends them to the loudspeaker. What you hear are the 1,000 Hz beeps. The T400P in CW mode transmits true keyed-carrier CW. A CW capable receiver receives the carrier pulses and converts them into beeps. The beep frequency can be varied by adjusting the tuning of the CW receiver. You track the transmitter with a directional antenna, and you get the loudest signal and audio tone beeps when the antenna is pointed directly at the transmitter. There are several low cost commercial receivers and handy talkies available that can pick up AM at 433.92 MHz. CW receivers are more complex and cost more. The T400P sends out your call sign (or other string of programmed characters) every 85 seconds, in Morse Code at 12 wpm.
To locate the transmitter at a distance, turn on the receiver and set it to the correct mode and frequency. Point the directional antenna outward, and slowly rotate your body until you can hear the signal. The signal audio is loudest when the antenna is pointed directly at the transmitter. Slowly wave the antenna back and forth to hear the signal strength drop off. You can quickly determine the direction of the loudest signal. Also, you should twist the antenna through all angles of vertical to horizontal orientation (polarization) for the loudest signal.
Programming the T400P Transmitters
The T400P (all formats) is user programmable with the userís call sign (or other single string of characters), and for mode, AM or CW. The letter "P" indicates that the particular model is programmable. Adept makes other models that are programmable, and some that are not.
Programming is accomplished by "keying" the programming pin to GND at about 12 wpm. On most of the programmable models, a small socket connector is provided. Slip a thin piece of wire into the connector so that a clip lead can be attached. Connect a second clip lead to GND at any of several points, such as on the negative side of the battery, or on the outside of the antenna connector (BNC or SMA if included).
Connect the programming pin clip lead to one side of a normally-open spst pushbutton switch, such as a hand key, and the other side to GND on the transmitter. Power up the transmitter, then momentarily close (dash length) the key or pushbutton switch within 10 seconds. Then immediately enter your call sign (or other single string of characters) in code at about 12 wpm.
For instance, to program a T400P-BNC, with the call sign WA4JBU, and to AM mode, key in the following string of characters. You must start within 10 seconds of powering up the transmitter.
The first dash (the T) puts the transmitter into programming mode.
To program the mode to CW, key in a dot (the letter E) after the first dash. Then key in the call sign.
The first dash (letter T) puts the transmitter into programming mode. The following dot (letter E) tells it to set the mode to CW. Be sure to key in the whole string as if it is one single word.
Programming Characteristics and Limitations
If the program keying is clean and with good spacing, the keying speed can be within the range of 6 to 18 wpm. At 12 wpm the "signal element" or dot length is 100 mS. The dash length is 300 mS. The space between elements of a letter is 100 mS, and the space between letters in a word is 300 mS. The Adept transmitters use a 200 mS decision time to determine if the input is a dot or short space, or if itís a dash or long space. If the key down input is less than 200 mS, a dot is assumed. If more than 200 mS a dash is assumed. The dash or long space can be up to two seconds. If more than two seconds, the programming routine will exit.
The code message is limited to one continuous string of up to about 15 letters depending on their lengths. The string cannot be programmed to two or more separate words. In place of a space, use a character such as a comma or the break character BT.
|www.adeptinstruments.com Copyright © 1989-2013 Adept Instruments, Inc., All Rights Reserved 10-2-13|