Midland 13-509 Receiver Squelch Modification

Better Squelch Action on the Midland 13-509
By Bob Dengler NO6B

Concept:
Modify the squelch found in the Midland 13-509 radio for better performance.

Modification information:
1. C89: replace 4.7 uF with 1 uF or 0.33 uF (I think I used 1 uF; 0.33 uF made the squelch action a bit too choppy).
2. C91: replace 4.7 uF with 0.47 uF
3. Add a 1 megohm resistor between base of TR13 & collector of TR14. This adds hysterisis which allows the squelch tail to be shorter without chopping, similar to how the G.E. MVP squelch works. See the image below for help with the resistor placement.