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The E-Comm frequency modulated FM transceiver is encased within a robust yet eye-catching metal box smaller than 6 inches in length.
Transmitter Diagram FIG. The enclosure incorporates a standard rechargeable nickel - cadmium power pack that should help you save the expense of frequently changing eight AA alkaline cells. The E -Comm receiver features a excellent 0. E -Comm owes its efficiency to its revolutionary Class -E final amp that displays substantial power gain. Receiver Diagram It gives a consistent output of 3 watts rms into a 50 ohm antenna or dummy load.
The economical receiver and the rechargeable power supply have the ability to maintain E -Comm within the air in the squelch mode -for 80 hrs without the need of recharging the power pack. The topic of this post is really a edition created for Using improvements to the transmit and receive filters part value variations working approximately 60 MHz is achievable.
This makes it possible for the transceiver to perform both the six- and ten - meter amateur radio wavelengths. The detachable seven-inch antenna is combined into the transceiver using a 50 -ohm bayonet -style BNC connector connector. Each of the components other than the battery pack, microphone, and speaker are attached to the double-sided PC board. Just how it had been developed The transceiver features 3 most important stages: transmitter, receiver, and power supply. Refer Figs.
Signals detected by the antenna are preselected through the 5 pole transmit bandpass filter which involves inductors L4, L7, and L5 and capacitors C11, C2, and C30 as indicated on the right side of Fig. This stage delivers an extra 2 poles of preselection. Diodes D1 and D2 protect against overloading and the likely damage of the RF amplifier transistor in case it is encountered with overdriving at the front end.
The preselected transmission is subsequently amplified by the IC3 MC internal common-emitter RF amplifier stage and given to the 1st mixer stage on pin 1. The RF amplifier comes with a gain of around 20 dB. The 1st local oscillator LO pulls a 3rd overtone from a crystal, and runs the 1st mixer by using a inner cascode amplifier.
Down conversion helps make the 1st LO frequency the first IF frequency For instance, if a The mixer is actually a two times as balanced multiplier that delivers around 18 dB of conversion gain. The output of the mixer is an emitter-follower stage having an output impedance of ohms to complement the ceramic filter. Filter F2, a The 2nd mixer pulls out a signal from the The limiter stage snip the kHz second IF signal to eliminate undesirable amplitude modulated signals and link with the audio detector.
A quadrature detector inside IC3, the MC, picks up the modulated signal. The parallel quadrature detector tank, L10, inside the detector is fine alligned to KHz. The demodulated audio transmission at pin 16 of the FM transmitter ICI is subsequently cleaned by an active filter stage that consists of an op amp inside of IC3, the FM receiver chip in Fig.
Resistor R10 in between pins 12 and 13 delivers hysteresis within the squelch circuit in order to avoid unnecessary "shoot through. Power usage is minimized by turning off the audio amplifier should the receiver is squelched, plus its additionally held low since it is operated through the un-controlled power supply along with the 32 ohm speaker.
This particular set up retains receiver consumption just at 7 mA from the battery pack once the receiver is in the squelch mode. Resistor R11 in between pins 4 and 5 fixes the amplifier gain, and the output of the amplifier operates the FM modulator. An adjustable reactance within the modulator "twists" the crystal frequency controlled oscillator stage.
In the E -Comm. Inductor L9 in series with XTAL3 in between pins 1 and 16 of IC1 fine tunes the oscillator frequency in the absence of a modulation supply. The oscillator buffered output on RF OUTPUT pin 14 subsequently supplies a tank circuit consisting of inductor Ll and capacitor C8, that is aligned to the 3rd harmonic of the oscillator. The transmission is increased with a factor of 3 to get the carrier frequency within this tank circuit.
The carrier and the modulation signal together are multiplied to acquire the 5 kHz deviation demanded by the receiver. After this, the signal is transferred via a tuned common emitter amp to boost and soften the carrier. Variable capacitor C30 adjusts the output stage to match up the antenna or dummy load. Observe that for getting class E working, both the load and the multiplier stages has to be adjusted relative to guidelines within the Calibration and "lineup section of this article.
Mismatch and overload security are offered through Zener clamp D4 Fig. The low voltage regulator demonstrated in Fig. The regulated output is determined by resistor R18 pin 6 and R28 at 6.
Due to the fact the voltage regulator is a CMOS device, resistor with higher values are positioned in the feedback loops for additional decrease of power usage. The power pack includes 8 AA nickel cadmium rechargeable cells, each rated at 1. The pack is recharged via connector J2 Fig.
Constructing the transceiver using SMD Surface mount devices SMD have been preferred for E -Comm simply because they encourage the structure of a smaller transceiver, and their tiny part dimensions make sure that PC board footprints are short. Having said that, never try to build this transceiver if you are not yet an established project builder. Because of this it is necessary to be particularly cautious to prevent confusing chip elements prior to and through the construction.
Professional equipment must be employed in picking and inserting SMD parts. They must be well suited for gripping tiny, difficult to handle components. Recommended ones are stainless tweeezers having needle point curved-end for picking and placing small parts for example chip resistors, capacitors and diodes within the PCB.
Carry out all soldering using a high-quality pointed to 15 -watt pencil type soldering iron. A lit up magnification glass will probably be beneficial, ideally one which brackets around the border of a table. Maintain fine solder eliminating desolder wik readily available to mend any kind of errors you could possibly make. Anybody developing E -Comm must be psychologically ready for the remarkably tiny scale of the SMD parts and their close spacing.
Dealing with SMD parts requires next to professional grade soldering abilities and plenty of endurance.
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