Progress Summary

58. Install C9, 1µF electrolytic capacitor. Check polarity when installing.

59. Install C11, 10 µF electrolytic. Observe correct polarity before installing.

60. Install R16, 270 ohm [red-violet-brown].

Now is a good time to take a break. Examine your work so far checking things such as component values, parts placement, and solder connections. Remember the old adage “The bigger the glob the better the job” does not hold true with RF electronics!

To this point, we have assembled a majority of the receiver. The RF, LO, IF and Demodulator sections have been built leaving us with the final audio stage, RSSI circuit, and AGC circuit. Sound like a lot more work? Not at all; we are going to take advantage of today’s power packed ICs! The LM386 audio chip takes care of our audio needs while the LM358 opamp is used two-fold in the RSSI and AGC circuits!

61. Install C29, .1µF ceramic disc capacitor [marked .1 or 104].

62. Install U1, the LM358 8 pin IC. Do not confuse it with the other IC; read the chip marking carefully. You will notice a notch, band or dot on one end of the IC. This should be oriented as shown on the parts layout diagram and PC board silkscreen. Be sure the part is seated close to the PC board before soldering all 8 pins.

63. Install R17, 1K ohm [brown-black-red].

64. Install R18, also 1K ohm [brown-black-red]..

65. Install J2, the subminiature speaker-headphone jack.

66. Install C12, .1µF ceramic disc capacitor [marked .1 or 104].

67. Install R15, 2 ohms [red-black-gold].

68. Next, install U2, the LM386 audio amplifier IC. As with U1, orient the notched or dotted end as shown in the parts layout diagram and on the PC board silkscreen. Solder all 8 pins.

69. Install C14, 220µF electrolytic capacitor. The positive lead of the capacitor must be placed in the hole next to the ( + ) sign.In the same way,

70. Install C13, placing the positive lead in the correct PC board hole. Remember, the banded side indicates the negative lead.

•71. Install the 9-volt battery snap connector, making sure that the red ( + ) black ( - ) leads are inserted correctly.

SR2 – 18

SR2 specifications

The Ramsey Electronics SR2 is a versatile and robust RF transmitter designed for a range of applications, including hobbyist projects, educational purposes, and practical uses in the field of amateur radio. Its compact size and user-friendly design make it a popular choice among enthusiasts and professionals alike.

One of the standout features of the SR2 is its frequency range, which typically spans from 88 MHz to 108 MHz. This wide range allows users to operate within the FM band, making it suitable for transmitting audio signals, music, or voice communications. This flexibility is particularly advantageous for those interested in creating their own radio stations or conducting experiments in radio frequency communication.

The SR2 utilizes advanced technology to ensure high-quality transmission. It incorporates modulation techniques that enhance audio clarity and reduce noise, resulting in a smoother listening experience. The transmitter is also equipped with a low distortion audio preamplifier, ensuring that sound quality remains pristine even at higher transmission stages.

Another important characteristic of the SR2 is its ease of assembly. The kit comes with all necessary components, including a printed circuit board (PCB), which simplifies the building process for users. Detailed instructions guide the user through the assembly, making it accessible even for those with limited electronics experience.

The SR2 also boasts a power output of approximately 100 mW, allowing for a transmission range of up to several miles, depending on the surroundings and antenna used. This power level strikes a balance between effective transmission and energy efficiency, catering to various operational settings.

In terms of design, the SR2 features a compact enclosure that protects the internal components from dust and damage, which is vital for maintaining reliability in various environments. Its user-friendly interface includes adjustable controls for tuning and volume, enabling users to customize their transmission settings easily.

Additionally, the SR2 is compatible with a variety of external audio sources, such as microphones, CD players, and smartphones, enhancing its versatility. The unit can be powered by standard power supplies or batteries, making it suitable for both portable and stationary use.

Overall, the Ramsey Electronics SR2 is a well-designed RF transmitter that combines quality, functionality, and ease of use, making it an excellent choice for anyone looking to explore the world of radio transmission.