Henning Weddig DK5LV says he is in the process of using an op amp and SSM2166 on his “original” BITX40 as a way of achieving an audio AGC function.
This op amp has a gain of 10 (20 dB) and an audio AGC system. He purchased a pcb from ZL1CVD with the DIL chip via ebay years ago. Unfortunately ZL1CVD does not sell this pcb any more…
The SSM2166 has a dynamic range of 60 dB, the opamp in front of it is intended to replace the first discrete amplifier after the demodulator and will amplifiy the audio into a range the SSM2166 can handle. The SSM2166 has a provision for outputting an AGC voltage (an RMS output) and this may be able to be used for driving an S-meter.
Others are thinking along the same lines. For example, Glenn VK3PE says:
“I’m thinking along the same lines. I built a Mic amp version using the SSM2167 and thought it might work also for the Receiver. It’s essentially the module seen on ebay but I’ve added a level pot on the output side.”
Meanwhile Alex PA1FOX comments:
“I am using the AGC from the original uBitx design, but found the time constant of 1uF and 100k to be far too low. This makes it a very fast AGC, not producing a nice sound with voices. I changed to 1.5 uF and 4M7 and now stronger stations are nice and clear (they ‘push’ the noise level down ) and the gain comes up nice and easy when the QRG is clear. I think I’ll keep it this way.”
One Reply to “SSM2166 (Mic amplifier and compressor) as Audio AGC?”
Comments are closed.