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Radio Broadcast Technical Consulting and Sales
 10032 Island Drive, Brainerd, MN  56401

 

Technical Tips from Mark W. Persons

Standards...Standards...How would we get along without them?
FM Composite Audio: 
For older Harris FM exciters such as the MS-15, the MX-15, and THE-1, 2.828 Volts Peak to Peak/1.0 Volts RMS will result in 100% modulation.
For Moseley STL systems, Broadcast Electronics FM Exciters, Bext, and newer Harris FM exciters, 3.5 Volts Peak to Peak/1.237 Volts RMS will give 100% modulation.
Audio Wire Color Coding on 2-pair shielded cable:
Green = left +
White = left -
Red = right +
Black = right -
XLR-3 (A3M or A3F) Connector Audio: 
Pin 1 = Shield
Pin 2 = Audio +
Pin 3 = Audio -

RJ-45 connector pin-outs found here.

For air variable capacitors, .045" plate spacing = 2kV rating  .075" plate spacing = 3kV rating  .080" plate spacing = 3.5 KV  .125" plate spacing = 4.5 kV rating.

According to a publication by Nautel, here are recommended settings of air arc-gaps when used at a 50 ohm zero reactance point in an AM transmission system:

 Radio Frequency:  Power Correction:
 540 KHz = .159 inches  1000 watts,  multiply by 1.05
 1000 KHz = .125 inches  5000 watts, multiply by 1.30
 1700 KHz = .076 inches  10,000 watts, multiply by 1.83

See examples of arc-gaps here.

The stories go on and on.  Stop in again sometime.  I'll leave the soldering iron on for you. 
Mark W. Persons   Ham WØMH

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page last edited 06/25/2011