VHF FM Aircraft Receiver
VHF FM Aircraft Receiver


VHF FM Aircraft Receiver


VHF FM Aircraft Receiver is a superregenative receiver developed for listening to FM transmitters but also tunes the aircraft band and the top portion of the FM broadcast band. Receives both AM and FM (107mHz to 135 MHz). You can use this receiver with the any FM transmitter. The receiver is amazingly simple using only one transistor for the receiver section and one IC for the audio section. This circuit is a self-quenching regenerative RF receiver also known as a superregenerative receiver. A superregenerative receiver performs two basic functions. First it feeds back a portion of the received signal from it’s output in phase to its input; and second a super audible quenching oscillator drives the amplifier through the point of oscillation and maximum sensitivity and then quenches the oscillation repeatedly. This keeps the feedback from driving the circuit into self-oscillation and allows the signal to be regenerated over and over again. In this version of the circuit, both functions are performed by the circuitry associated with Q1. The rest of the circuit, shown to the right of L3 in the schematic, comprise the audio amplification circuit and are centered on the LM386 Audio Amp IC. In this configuration the LM386 is set at a gain of 200 and feeds it’s output to a standard 1/8-inch diameter stereo phone jack. The audio can then be heard by plugging any standard stereo headset into the jack.

VHF FM Aircraft Receiver

The controls consist of C1, C2, R3 and R6. C2 provides the frequency selection. C1 provides fine-tuning, R3 adjusts sensitivity and R6 is the volume control.

Connect a 9-volt radio battery to the battery connector and a stereo headset to the speaker jack. You should hear a hissing noise if your receiver is working. Tune the receiver by adjusting C2 with a non-ferrous tool. C1 can be used to fine-tune the circuit or to shift the tuning range of C2 (increase the capacitance of C1 if you want to receive FM broadcast below 107 MHz). With C1 In its highest capacitance position C2 will tune the receiver through the lower portion of the aircraft band and the top portion of the FM broadcast band. With C1 in its lowest capacitance position C2 will tune the receiver through the aircraft band and a little higher.

C2 is at its highest capacitance when the small dab of solder on the top of C2 is lined up with the middle pin. A good way to set the receiver to receive a signal from a 108 MHz transmitter like the FM108 tracking transmitter is to set C2 slightly to the right of its highest capacitance and then tune C1 until you hear the signal from the 108MHz transmitter.

Listening to the aircraft band

You may have to tune around a bit and listen for a while before hearing any aircraft transmissions. Pilot communications are generally short and to the point. Transmission is limited to a few seconds. Since VHF communications are “line-of-sight” you will be able to hear aircraft at 30,000 feet a100 miles away or more but may not be able to hear the control tower that is only 10 or 20 miles away if your view is obstructed by buildings or hilly terrain..

One thing to watch out for is strong local signals. The received signal may be garbled if the signal is too strong. This is usually the case when tuning FM broadcast band stations. To remedy this problem turn the sensitivity to its lowest point and put the antenna in the down position.

Radio Tracking the FM108 transmitter
Hold the radio with the antenna fully extended against the front of your body shielding the antenna with your body. Slowly turn while listening to the “beeping” signal from the FM108 transmitter. The beeping will be the loudest when you are facing the transmitter. If the “beeping” is loud when facing all directions then lower the antenna to the point where you can barely hear the signal when facing in one direction. Continue to reduce the length of the antenna as you approach the transmitter.

Why doesn't the VHF1 receiver use a directional beam or yagi antenna??
A directional beam antenna for this frequency would be to large for field work. Such an antenna would be over four feet wide and would present a considerable problem moving through brush and trees. The relative short telescoping antenna when shielded by the operator’s body works very effectively for direction finding and is relative easy to work through heavy brush and trees. This technique is sometimes referred to as "Body Fade" and it produces a cardioid sensitivity pattern (see picture). The peak null position is exactly 180 degrees opposite the transmitter.

As mentioned above, the operator should take a reading by holding the receiver against their stomach (the edge of the receiver opposite the antenna should be touching the stomach area). The antenna should extend vertically and be about 6 inches in front of the face. Turn slowly listening for the strongest signal (loudest beeping). Move in the direction of the strongest signal (opposite the direction of the weakest signal). Periodically stop and take another reading, adjust the course and continue to work towards the transmitter. Since the “null” point is much narrower than the maximum signal point it may be easier to use the “null” point to establish the most accurate direction to the transmitter. With a little practice a person can become quite efficient in locating the transmitter although the path taken will be somewhat zigzagged.

L1 .12 uH coil
L2 .15uH
L3 .68 uH coil
L4 .82 uH coil
Air wound; 1.5 turns
on 3/8 form
#26 insulated wire
R1 680 ohm
R2 33K
R3 50K pot
R4 10K
R5 6.8K
R6 5K pot
C1 2 - 5 pF trimmer
R7 10 ohm
C2 2.5-12 pF trimmer
C3 22pF
Q1 NTE 108 Transistor
C4 6.8pF
IC1 LM386
C5,C11 .002 uF
C6 .001 uF
C7 1uF
C8 1000 uF
C10 .047 uF
C12 10 uF
C13, C15 0.1 uF
C14 220 uF

VHF FM Aircraft Receiver

VHF FM Aircraft Receiver

VHF FM Aircraft Receiver

Accurate LC Meter Capacitance Inductance Meter with 16F628 and LCD
Volt Ampere Meter with 16F876 Microcontroller and LCD display
Accurate LC Meter

Build your own Accurate LC Meter (Capacitance Inductance Meter) and start making your own coils and inductors. This LC Meter allows to measure incredibly small inductances making it perfect tool for making all types of RF coils and inductors. LC Meter can measure inductances starting from 10nH - 1000nH, 1uH - 1000uH, 1mH - 100mH and capacitances from 0.1pF up to 900nF. The circuit includes an auto ranging as well as reset switch and produces very accurate and stable readings.
PIC Volt Ampere Meter

Volt Ampere Meter measures voltage of 0-70V or 0-500V with 100mV resolution and current consumption 0-10A or more with 10mA resolution. The meter is a perfect addition to any power supply, battery chargers and other electronic projects where voltage and current must be monitored. The meter uses PIC16F876A microcontroller with 16x2 backlighted LCD.

50MHz 60MHz Frequency Meter / Counter with 16F628 & LCD
1Hz - 2MHz XR2206 Function Generator
60MHz Frequency Meter / Counter

Frequency Meter / Counter measures frequency from 10Hz to 60MHz with 10Hz resolution. It is a very useful bench test equipment for testing and finding out the frequency of various devices with unknown frequency such as oscillators, radio receivers, transmitters, function generators, crystals, etc.
1Hz - 2MHz XR2206 Function Generator

1Hz - 2MHz XR2206 Function Generator produces high quality sine, square and triangle waveforms of high-stability and accuracy. The output waveforms can be both amplitude and frequency modulated. Output of 1Hz - 2MHz XR2206 Function Generator can be connected directly to 60MHz Counter for setting precise frequency output.

BA1404 HI-FI Stereo FM Transmitter
USB IO Board PIC18F2455 / PIC18F2550
BA1404 HI-FI Stereo FM Transmitter

Be "On Air" with your own radio station! BA1404 HI-FI Stereo FM Transmitter broadcasts high quality stereo signal in 88MHz - 108MHz FM band. It can be connected to any type of stereo audio source such as iPod, Computer, Laptop, CD Player, Walkman, Television, Satellite Receiver, Tape Deck or other stereo system to transmit stereo sound with excellent clarity throughout your home, office, yard or camp ground.
USB IO Board

USB IO Board is a tiny spectacular little development board / parallel port replacement featuring PIC18F2455/PIC18F2550 microcontroller. USB IO Board is compatible with Windows / Mac OSX / Linux computers. When attached to Windows IO board will show up as RS232 COM port. You can control 16 individual microcontroller I/O pins by sending simple serial commands. USB IO Board is self-powered by USB port and can provide up to 500mA for electronic projects. USB IO Board is breadboard compatible.

ESR Meter / Transistor Tester Kit
Audiophile Headphone Amplifier Kit
ESR Meter / Capacitance / Inductance / Transistor Tester Kit

ESR Meter kit is an amazing multimeter that measures ESR values, capacitance (100pF - 20,000uF), inductance, resistance (0.1 Ohm - 20 MOhm), tests many different types of transistors such as NPN, PNP, FETs, MOSFETs, Thyristors, SCRs, Triacs and many types of diodes. It also analyzes transistor's characteristics such as voltage and gain. It is an irreplaceable tool for troubleshooting and repairing electronic equipment by determining performance and health of electrolytic capacitors. Unlike other ESR Meters that only measure ESR value this one measures capacitor's ESR value as well as its capacitance all at the same time.
Audiophile Headphone Amplifier Kit

Audiophile headphone amplifier kit includes high quality audio grade components such as Burr Brown OPA2134 opamp, ALPS volume control potentiometer, Ti TLE2426 rail splitter, Ultra-Low ESR 220uF/25V Panasonic FM filtering capacitors, High quality WIMA input and decoupling capacitors and Vishay Dale resistors. 8-DIP machined IC socket allows to swap OPA2134 with many other dual opamp chips such as OPA2132, OPA2227, OPA2228, dual OPA132, OPA627, etc. Headphone amplifier is small enough to fit in Altoids tin box, and thanks to low power consumption may be supplied from a single 9V battery.

Arduino Prototype Kit
RF Remote Control 433MHz Four Channel
Arduino Prototype Kit

Arduino Prototype is a spectacular development board fully compatible with Arduino Pro. It's breadboard compatible so it can be plugged into a breadboard for quick prototyping, and it has VCC & GND power pins available on both sides of PCB. It's small, power efficient, yet customizable through onboard 2 x 7 perfboard that can be used for connecting various sensors and connectors. Arduino Prototype uses all standard through-hole components for easy construction, two of which are hidden underneath IC socket. Board features 28-PIN DIP IC socket, user replaceable ATmega328 microcontroller flashed with Arduino bootloader, 16MHz crystal resonator and a reset switch. It has 14 digital input/output pins (0-13) of which 6 can be used as PWM outputs and 6 analog inputs (A0-A5). Arduino sketches are uploaded through any USB-Serial adapter connected to 6-PIN ICSP female header. Board is supplied by 2-5V voltage and may be powered by a battery such as Lithium Ion cell, two AA cells, external power supply or USB power adapter.
200m 4-Channel 433MHz Wireless RF Remote Control

Having the ability to control various appliances inside or outside of your house wirelessly is a huge convenience, and can make your life much easier and fun. RF remote control provides long range of up to 200m / 650ft and can find many uses for controlling different devices, and it works even through the walls. You can control lights, fans, AC system, computer, printer, amplifier, robots, garage door, security systems, motor-driven curtains, motorized window blinds, door locks, sprinklers, motorized projection screens and anything else you can think of.

Electronics-DIY.com © 2002-2022. All Rights Reserved.