• ROHM's wireless audio link ICs (FM transmitter) enable the smallest FM stereo broadcasts
• Compatible with billions of FM radio receivers around the world
• Removes noise contained in digital audio sources, resulting in hi-fi sound
• Built-in high-performance digital transmitter ensures stable transmission of broadcast waves
• A PLL circuit, stereo modulator, FM transmitter, and the like are all consolidated into a single package
• Conforms to the global standard GE Zenith (Pilot Tone) system

Hi-fi stereo sound that rivals that of a conventional broadcast station

Specialized, high-performance circuit designs make it possible to deliver high-fidelity sound equivalent to a radio station.

Application Examples

TVs, DVD players, Set top boxes, Portable music players, Wireless headphones, Wireless speakers, PCs, PC mice, PC peripheral equipment, Cordless phones, Coffee makers, Microwaves, Ovens, Mobile phones, Digital cameras, Gaming consoles, Battery chargers, Calculators, Personal data assistants, Clocks/watches, Illumination equipment, Student desks, Dressers, Bathtubs, Vending machines, ATMs, On-board music systems, Ticket vending machines, and more

Specifications

It had only been eleven years since Guglielmo Marconi sent the first "wireless" transmission with his new invention, and only five since Marconi sent signals across the Atlantic. Making use of the high-frequency alternator, Canadian-born physicist Reginald A. Fessenden made his historic Christmas Eve broadcast, in which he transmitted music as well as human speech.

Another early broadcast took place in 1910 when Lee de Forest, inventor of a type of vacuum tube called a triode, aired programs from New York's Metropolitan Opera House.

But it was not until 1916, when a Westinghouse engineer named Frank Conrad played records for his friends over the air, that the idea of radio as a public medium took shape.

An executive at Westinghouse heard about Conrad's broadcast and realized its potential. Here was a medium available to the masses -- a huge potential audience. An audience that would listen to radio broadcasts... with radios made and sold by Westinghouse.
In 1920, Westinghouse's KDKA began regular broadcasts. That same year it aired the results of the 1920 presidential election before the results could be read in the papers. This caused a sensation and is considered the beginning of professional broadcasting.

FM signals have a great advantage over AM signals. Both signals are susceptible to slight changes in amplitude. With an AM broadcast, these changes result in static. With an FM broadcast, slight changes in amplitude don't matter -- since the audio signal is conveyed through changes in frequency, the FM receiver can just ignore changes in amplitude. The result: no static at all.

为了展示我国电子工业水平，为了使来我国大饭店居住的国际友人能够及时地收听到来自自己国家的消息和声音，北京无线电厂立即组成了北京饭店高级半导体收音机设计小组，确定了“牡丹”2241调频调幅全波段台式一级收音机的设计方案。

经过一段时期的研制，“牡丹” 2241傲然开放。73岁的北京无线电厂前总工程师严毅回忆说，测试接收效果时，将“牡丹”2241收音机与日本索尼（SONY）的一台同类的收音机进行了比较，接收效果毫不逊色。那台索尼的机器在日本被称作收音机之王，“牡丹”2241应该是中国的收音机王！”

“牡丹”2241是北京无线电厂牡丹系列晶体管台式机的经典作品，但北京无线电厂值得骄傲的却不仅仅是2241。实际上，上个世纪50年代至90年代，北京无线电厂的“牡丹”牌收音机在北京乃至全国一直占据着主导和领先地位，它曾被誉为我国收音机的“四大名旦”之一，名扬海内外。

1956年3月11日大声无线电商行、中国无线电业商行等27家私营企业成立了公私合营广播器材厂（北京无线电厂前身）

1958年，牡丹商标审定书

郭沫若题写的牡丹商标标牌

早期的牡丹矿石收音机

1960年，刘少奇将牡丹收音机当成国礼送给外宾

陈毅为外宾演示牡丹收音机

1963年牡丹8402收音机研发大会战

牡丹8402收音机，它是1963年北京市组织的半导体收音机的试制大会战的成果

文化大革命期间，牡丹被改名红旗

文化大革命期间的红旗收音机643型

鉴于大量出口产品的需求和用户的要求建议恢复使用“牡丹”商标，1971年9月首次恢复使用“牡丹”牌商标出口644型半导体收音机。

1974年何起蛰、俞锡良设计的大型台式牡224l型22管全波段半导体收音机。

牡丹收音机厂生产车间

当年的北京无线电厂大门

北京无线电厂外景

北京无线电厂后改称益泰集团。这是益泰集团的员工参与鸟巢奥运监控设备的建设

OK. So we have a signal that is sent to a radiosmitter's antenna. How does that signal get from the antenna to the air?

Let's first take a look at the signal. The signal is an electic current, and every electric current is actually electrons moving in a wire.

Wire is made of metal, usually copper. All of the atoms that make up the wire have something in common -- each has one or two electrons in its outer-most shell.

These electrons do not have a strong bond with the rest of the atom. In fact, it takes just a slight amount of energy to push the electron away from its atom.

But if you have enough energy, the outer electrons from all of the atoms will move at once. They will each travel from one atom to the next atom, and so on.

Back to our radio signal. The electrons in our wire are moving, but not in one direction. These electrons are moving back and forth.

Actually, the wave displayed in the activity is a representation of the back and forth movement of electrons. If the wave has a frequency of 200,000 Hz (cycles per second), the electrons in the wire are moving back and forth 200,000 times a second.

When electrons move in a wire, an electromagnetic field is created around that wire. There's no magic behind this; it's just the way things work.

Just as the electrons move in the wire, they move in the transmitter's antenna. And just as an electromagnetic field is created around the wire, a field is created around the antenna.

But there is a difference between the wire and the antenna. The wire is shielded (surrounded by another wire) to keep the electromagnetic field in. The antenna, on the other hand, is designed to radiate the electromagnetic field.

The electromagnetic field travels from the antenna in all directions and at the speed of light. It travels until it hits your radio's antenna as well as hundreds of other receiving antennas.

And what happens at the receiving antenna? Just as a current in a wire produces an electromagnetic field, an electromagnetic field produces current in a wire (or antenna). This current is then amplified and processed by the radio.

265MHz UHF frequency transmitter is made up of V1 and external components C1, C2, L1, L2, etc. through the loop antenna L2 to the air-launched. L2 antenna use  silver-plated wire of the enameled wire diameter of 1.5mm. Antenna size is 24mm (long) X9mm (H). V1 Selection of high-frequency triode  BE414 or 2SC3355.

Part of the Radio-controlled Receive, Working voltage of 6V, waiting for the 1mA current. Receive frequency of 265MHz.

Receiver circuit primarily by V1, IC and other components, V1 and C7, C9, L2 components, such as ultra-high frequency receiver circuit. C9 to change their receivers to fine-tune frequency, so that strict firing frequency at 265MHz. Antenna size is 24mm (long) X9mm (H). V1 use BE415 or 2SC3355. Capacitor C9 may choose to use a small adjustable capacitor. IC use LM358.

All resistors use 1/8W or 1/16W Metal Film Resistors. Electrolytic capacitors are also used ultra-small capacitance. All other capacitance use high-frequency ceramic capacitors.

IC1, C1 component of the about 400HZ low-frequency oscillator; IC2, C3 component of the about 37MHZ high-frequency oscillator, C2 output from the low-frequency signals of high frequency modulation signals. C4 and antenna composition launch system. High-frequency harmonic oscillator in three TV channels to receive (or other channel) show a black-and-white section of the grid signal. A point, B point of the output signal, respectively, and the images of low-frequency channel for the detection of signal source. The C3 can replace quartz crystal oscillation frequency stability, as shown in Figure dashed part. C3 if the Department received a terminal or socket, to C3, respectively, into crystal; frequency selected 465KHZ, 10.7KHZ, 6.5KHZ, 4.43MHZ, 37MHZ can do on the radio and TV-IF signal source.

Token Resistor Color Code

CXA1191M Radio circuit