Title: FT-102 Circuit Modifications for High Fidelity AM Post by: Steve - K4HX on December 22, 2012, 12:23:39 PM FT-102 Circuit Modifications for High Fidelity AM AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
by Bill, W3DUQ AF Board
Note: If you desire to use the phone patch input for external audio feed, put 220k in series with the center conductor going to the patch input jack and a 1k to ground from the input audio side of the phone patch jack. Also remove C04 (10 uF) from the AF unit to reduce the overall audio gain. I also changed R11 from 2.2k to 15k to set the gain properly for vox operation. AM/FM Board
Set both tone controls on the AF board to 50%. Frequency response is essentially flat from 40-6khz and down 3db at 16 khz. If you want it flat to 16 khz, just turn up the treble tone control a bit. There is a problem with the ALC kicking in too early on AM. To fix this, connect a 10k resistor between pins 2 and 3 of P22/J15 on the I-F board. This will raise the point at which the ALC kicks in. |