.....obsolete user manuals, a lot of repair manuals, free service manuals, rare schematic diagrams, usefull service instructions, pdf books, how to repair instructions, lost operating manuals, old handbooks, tons of part lists, hidden service bulletins, your instruction books, informative repair tips, complete disassembly routines.....

What are you looking for?

extended search

Ramsey Electronics COM 3 Communications Test Set
Communications Service Monitor


The COM 3 is a lightweight, compact service monitor for testing AM and FM transceivers. The internal battery, which is a standard feature of the COM 3 combined with the optional carrying case and low weight (13 lbs), make it ideal for field use. Utilizing specially designed micro powered oven circuits, warm -up time is minimal, providing maximum use of the battery. The frequency range is 100 KHz to 999.999 MHz in 500 Hz steps. Standard CTS tones as well as a 1 KHz tone can be generated. RF power is continuosly variable in five ranges from 0.1 ¡iv to 10,000 ¡j.v. The display is a seven digit LED type which will display frequencies generated or received, CTS off air, as well as being an audio and RF frequency Counter. Deviation and frequency error are displayed on a 20 segment LED bargraph, which is easily visible from across the shop. An internal RF relay switches transmitted power greater than 500 mW to a rear panel mounted BNC connector. This protects the COM 3 from accidental keying and allows easy connection of an antenna, power meter, or dummy load.

show more

User Manual with schematics
Manual type:
User Manual with schematics
9.35 Mbytes (9806215 Bytes)
01 January 1987
Scanned document, all readable.
Upload date:
04 February 2017


Section 1 - General Information 1.1 Introduction 1.2 Specifications 1.3 Options 1.4 Special Modifications Section 2 - Installation 2.1 Introduction 2.2 Unpacking and Inspection 2.3 Power Requirements 2.4 Enviromental Considerations Section 3 - Operation 3.1 Introduction 3.2 Front Panel Description 3.3 Initial Turn On 3.4 Generate RF 3.5 RF Output Level 3.6 FM Modulation 3.7 AM Modulation 3.8 CTS Tone Generation 3.9 1 KHz Internal Tone 3.10 External Source Input 3.11 Combining CTS and Internal/External Tone Sources 3.12 Offset+/Offset- 3.13 500 Hz Step 3.14 Storing/Recalling Test Setups 3.15 Spurious Signals 3.16 Leakage 3.17 Audio Count Off Air 3.18 Audio Count External 3.19 RF Count Section 4 - Typical Test Setups 4.1 Introduction 4.2 Frequency Counter : Off Air 4.3 Frequency Counter : Direct Connection 4.4 Frequency / Deviation Measurements 4.5 20 dB Quieting Measurement 4.6 12 dBSinad Measurement 5.1 General 5.2 512-1018 MHz Coarse Loop PLL 5.3 5-7 MHz Fine Loop PLL - 5.4 1024 MHz Offset PLL 5.5 Output Step Attenuator 5.6 4 MHz Reference Standard 5.7 FM Modulator 5.8 AM Modulator 5.9 1 KHz Source 5.10 Receiver 5.11 16 KHz Reference Generator 5.12 Frequency Error Detector 5.13 Audio Amp 5.14 + 30 Volt and -10 Volt Supplies 5.15 Transmit Protection Circuit 5.16 DC Supply and Battery 5.17 Membrane Switch 5.18 Microprocessor 5.19 Display Drivers 5.20 Audio Frequency Counter 5.21 RF Frequency Counter 5.22 CTS Tone Generation 5.23 Frequency Error/Deviation Display Section 6 - Documents,Figures Fig 3.1 Front panel layout Fig 4.1 Block diagram Schematic diagram Warranty Test data

show more


No comments yet. Be the first!

Add Comment

* Required information
Captcha Image
Powered by Commentics