Experimental narrowband FM receiver for 2-meter band

This project is about MC3362 and ADF4351 based modularized, 2-meter narrow band FM receiver. In this design, the receiver splits into three modules as RF preamplifier, MC3362 tuner, and ADF4351 oscillator. The RF preamplifier builts around BF900 dual-gate MOSFET. The tuner stage builts using the popular MC3362, low power narrowband FM receiver IC. For the oscillator, we use the ADF4351 DDS RF signal generator module.

The core component of this receiver is MC3362 IC. This IC was designed by Motorola and is no longer in production, but this IC is still available to purchase in many online stores. The chip we used in this receiver was purchased from a local electronic component store for LKR 75 (USD 0.2).

The RF preamplifier used in this receiver extracts from the N.Ganesan's (VU3GEK) LRR200, 2-meter band FM receiver project.

Prototype version of the RF preamplifier.

In this prototype, the above preamplifier was built as a module using a Manhattan construction technique. The SO-239 antenna input socket is also soldered directly to the preamplifier board. The preamplifier output connects to the input of the 1st mixer stage of MC3362 via a 50Ω coaxial link. This preamplifier is designed to operate using an 8V DC power source. If the BF900 transistor is not available, use an equivalent dual-gate, UHF range, N-channel MOSFET transistor.

MC3362 tuner

The tuner stage of this receiver is a minimal version of the MC3362 circuit. This tuner module mainly consists of 10.7MHz and 455kHz ceramic filters, a 42IF301 - I.F transformer, and a 10.245MHz crystal. The local oscillator stage of this receiver is modified to use the ADF4351 RF signal generator. During the prototyping stages, we drive this module using a 5V DC power source.

ADF4351 DDS RF signal generator module.

For the oscillator stage, we use the ADF4351 DDS RF signal generator module. Apart from the ADF4351 signal generator, this module has an STM32F103-based driver and a TFT touch LCD. The RF output of this oscillator is directly connected to one of the local oscillator terminals of MC3362 IC. This module is designed to work with 5V. The supply voltage is feeding to the module through the onboard USB connector.

During the prototyping stages, we connect the AF output of this receiver to the TPA3001D1 power amplifier. Any AF power amplifier with 3W or higher rated output will work well with this receiver.

After connecting a suitable antenna, we were able to receive a very clear 2-meter band signal from the receiver. During the testing phase, we got extremely good reception of the RSSL VHF net at 145.625MHz (local oscillator frequency - 134.875MHz) from this receiver. For this test, we used a 5-element (homebrew) Yagi antenna.

RF preamplifier layout.

PCBWay sponsored this project. PCBWay offers high-quality PCB manufacturing, PCB assembly, and CNC/3D printing services for a competitive price. Check their website for more information and pricing.

All the KiCAD design files and schematic diagrams are available on google drive. The PCB of this receiver can be directly ordered from the PCBWay project page.

CD2003 - yet another simple FM radio receiver

In the last few days, we are looking for some simple FM radio receiver to integrate into one of our ongoing projects. For that, we try several FM radio receiver ICs including TDA7000, CD2003/TA2003/TA8164, CXA1019, and KA22429. Out of all those chips we select CD2003 (or TA2003/TA8164) based receiver for our project because of its simplicity and outstanding performance. Except to CD2003, Sony CXA1019 also perform well but we drop it because of its higher component count. We design our receiver based on Toshiba TA2003 datasheet and later we try TA8164 and CD2003 with the same circuit. Either CD2003 or TA8164 can directly replace TA2003 IC, and as per our observations, TA8164 gives excellent results out of those 3 chips. A prototype version of CD2003 FM radio receiver The PCB design and schematic which we used in our prototype project are available to download at google drive (including pin-outs of crystal filters and inductors ). Except for CD2003 IC, this receiver consist

Arduino superheterodyne receiver

In this project, we extend the shortwave superheterodyne receiver we developed a few years ago . Like the previous design, this receiver operates on the traditional superheterodyne principle. In this upgrade, we enhanced the local oscillator with Si5351 clock generator module and Arduino control circuit. Compared to the old design, this new receiver uses an improved version of an intermediate frequency amplifier with 3 I.F transformers. In this new design, we divide this receiver into several blocks, which include, mixer with a detector, a local oscillator, and an I.F amplifier. The I.F amplifier builds into one PCB. The filter stage, mixer, and detector stages place in another PCB. Prototype version of 455kHz I.F amplifier. In this prototype build, the Si5351 clock generator drives using an Arduino Uno board. With the given sketch, the user can tune and switch the shortwave meter bands using a rotary encoder. The supplied sketch support clock generation from 5205kHz (tuner frequ

Calculator for audio output transformers

Audio output transformers are heavily used in a vacuum tube and some (older) transistor base audio power amplifiers, but these days output transformer are quite hard to find and expensive item. For homebrew projects, the best option is to construct those transformers by ourselves and this script helps to calculate winding parameters for those transformers. This " AF output transformer calculator " script is written using Python and it works with most of the commonly available Python interpreters . The script is available to download at google drive under the terms of GNU General Public License version 3.0 . Homebrewed 25k: 4 output transformer Once supplied the input parameters this script provides a winding ratio, the number of turns required for primary and secondary winding and required copper wire gauges for both primary and secondary windings, etc. We construct several AF output transformers based on results of this script, which including transformers for M