Popular EBS System Modifications for EAS

These modifications downloaded from the Newsgroup - Rec.Radio.Broadcasting.


The outputs of the 107 Hz filters for the two tone decoders go into a diode, a parallel R/C circuit, another diode and combine into a voltage divider. Where these two diodes tie together, there is a 47 uF Tantalum capacitor. Change this to a 22 uF @ 16-25 volt Tantalum. The decoder will now activate at about 6 - 7 seconds.

On the encoder turn the 1 megohm Activate Internal Adjust pot counter clockwise until the tone is at 9 - 10 seconds(recommended). This modification may require a slightly longer closure of the activate switch to allow the timing capacitor to fully charge.


On the decoder board, replace C13 with a 22 uF 25 volt Tantalum capacitor. Replace R26 with a 182K ohm 1/4 watt 1% resistor. This will cause the decoder to activate in approximately 4 seconds.

On the encoder board, cut the trace at Z3 pin 1. Then jumper from Z3 pin 1 to Z4 pin 9. This will give 8.5 - 9 seconds of encode tone.

If you want to put in a 8.5/23 second encode select switch, install a SPDT switch on the back panel of the chassis with the common on Z3 pin 1 and the other switch terminals on Z4 pins 9 & 11 respectively, to select the tone times.


In the EBS-2 decoder, parallel R37 with a 560K ohm 1/4 watt 1% resistor. This should decode in 5.5 - 7 seconds.

In the TG-2 encoder, adjust the trimpot near the NE555 chip clockwise to 9 seconds.

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