RF Modulator

From GanjaLinux

Alpha: This project is in ongoing planning. The requirements are being worked on. Please join the effort.

Contents 1 Design Requirements 2 Learning 3 Inspiration 4 Electrical Components 5 Schematic Diagram 6 Examples

Design Requirements

• To be able to broadcast video and/or audio over selected channels of a CCTV network from a single or multiple control rooms.
• A return patch for a microphone intercom.
• Operate in the VHF range. Channels 2/3-4 minimum.
• Stereo audio modulation.
• rack mountable with control knobs on front of unit.

Learning

1. Maxim/Dallas Semiconductor APPLICATION NOTE 3551 Conditioning A/V Signals for RF Modulation
   • By Bill Stutz,Principal Member of the Technical Staff, Multi-Media Group, Maxim Integrated Products Inc., Sunnyvale, CA
   • http://www.maxim-ic.com/appnotes.cfm/appnote_number/3551

Inspiration

Retail Products

• http://www.aba-industry.com/aba_home_wiring_video_distribution_catv.htm
• Video Modulators - HomeTech Solutions
  • http://www.hometech.com/video/mod.html#CV-CVT3

Electrical Components

Datasheets

• LM139 LM239 LM339 LM2901 LM3302 Low Power Low Offset Voltage Quad Comparators http://www.national.com/ds/LM/LM139.pdf
  • Used in Radio Shack RF-Modulator similar to http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F003%5F010%5F009%5F000&product%5Fid=15%2D2526)
• MC1374 TV MODULATOR CIRCUIT Motorola http://pdf.alldatasheet.com/datasheet-pdf/view/3504/MOTOROLA/MC1374P.html
• LM2889 RF Modulator AN-402 National Semiconductor http://www.national.com/an/AN/AN-402.pdf
• MC44BC374 Multi-Standard Audio/Video Modulator Antenna Booster/Splitter
  • http://www.freescale.com/files/app_specific_stand_prod/doc/data_sheet/MC44BC373.pdf

Schematic Diagram

        C             ________                      
    .---||----+-----()________             
    |         |         Coax
    >         |)         
    < Rload   |) L
    >         |)
    |         |
    o Vgnd!  /+\ Microphone
             \-/ 
              |
              o Vgnd!
    
  Figure 1. Ensured path to coax for an unmodulated microphone signal.

Examples

Examples with schematics or layouts

• VHF/UHF TV modulator - Elektor january 1985 - DIY
  • http://members.tripod.com/~petlibrary/rfmod.htm