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If, like me, you sometimes want to use old used capacitors, what follows might interest you !
Why ?
When an aluminium capacitor is produced, it can't be used immediately. It must pass thru a generating process. This process consists in charging the capacitor with a very low current until it reaches its nominal voltage.
During this charging, a certain quantity of aluminium is teared off from the electrods and is deposited on the dielectric in the form of aluminium oxyd. This oxyd is an insulator that protects the dielectric up to a voltage at which it has been formed.
This oxyd layer is maintained and regenerated each time the capacitor is used by a small amount of current, called leakage current. The serious manufacterer are giving a maximum value for this leakage current.
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Unsoldering SMD components can be very frustrating, time consuming and a disaster. Here is a trick i've found in a electronic magazine of which i forgot the name.
All you need is a piece of enameled copper wire of about 0.2 to 0.3 mm in diameter.
Take a length of this wire and slide it under the pins of the circuit you want to unsolder. Attach one end firmly,( because you will have to pull on it ) in soldering it on a large pad close to the circuit.
Pull firmly on the free end of the wire so it leants again the first pin of the circuit. Do that while keeping the wire as close as possible to the printed board.
Heat the first pin, the enamelled wire should slip under the pin and raise it from the board.
Repeat this procedure for each pin, taking care not to break them. Double your attention for the last one, the wire being stopped by nothing.
Make some tests on a defective board before applying this method to a board you want to repair.
The smallest SMD components can't be unsoldered this way, you can't even slide a wire under the pins !
Let me know if this could help you and/or if you have a better method.
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Ilt is sometimes necessary to split the output of one transmitter in order to drive 2 amplifiers or 2 antennas. There are several ways to do that, but an elegant one is to use this splitter.
The following description is the fruit of my own experience and works perfectly.
This splitter is composed of 4 lengths of 75 Ohm coaxial cable.
During normal operation, the injected power in the input IN and split in 2 equal levels on outputs OUT1 and OUT2.
No power should be present on the 50 Ohm dummy load.
The signal available on ouput OUT2 (via a Λ/4 line) has a -90° phase, the one on OUT1 (via the 3Λ/4 line) has a phase of -270°. The signal arriving into the dummy load (via the 3Λ/4 + Λ/4 and Λ/4 +Λ/4 lines) has a phase of 180°, so is cancelled !
One advantage of this splitter is that the 2 outputs are insulated one from the other !
In case of a mismatch on one of the outputs, the other output is not (or very slightly ) affected. All the power normaly present into the output is dissipated into the dummy load. This later one should be able to safely handle half the input power.
This circuit can be used on any frequency, you only need to cut the lines to the right length.
CAUTION, the lines have to be made in 75 Ohm coaxial cable !!. Don't forget to apply the velocity factor (depends of the isolating material) when you cut your lines !
This circuit can be used in a reversed manner, for example when you want to couple 2 amplifiers into one output. In this case, the splitter is used in a reversed manner, OUT1 and OUT2 are respectively IN1 and IN2, and the output is on IN.
CONS
Works only on one frequency/band...
A bit large, coaxial lines can be long...
I hope this can be useful for you ...
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L'ATR2400 est un émetteur-récepteur de la marque ALCATEL, conçu à l'origine pour un fonctionnement dans la bande RADIOCOM 2000 de 414-428 Mhz.
Deux versions ont été construites, la plus répandue étant la version Duplex ATR2400 ERD avec écart de fréquence de 10 Mhz. Il existe une version ATR2400 ERA fonctionnant en alternat conçue pour les réseaux privés.
Espacement entre canaux : 12,5 Khz
Ecart duplex : 10 Mhz
Type de modulation : phase
Puissance émetteur : 2 ou 11 Watts commutable
Excursion maximale TX : 2,5 Khz
Puissance BF : variable par 6 bonds de 1 à 3 W
Sensibilité : 1,5uv pour S/B de 20 dB
Subcategories
Test equipements Article Count: 5
Antennas Article Count: 8
TS850 Article Count: 4
TS590 Article Count: 3
Cartes Article Count: 2
Radiosondes Article Count: 1
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