I have just finished building the VK3YE LED-LDR AGC circuit, for an MST-Mk1 (not BiTx40), but a similar rig. ?Write-up and demo video here:?
W0PWE>?It seemed like the AGC circuit was loading the audio coming from the pre-amp a bit so I added a resistor in series with the AGC amp - 33K if I remember correctly. I also tuned the resistor that is in series with the LDR.
I noticed the same thing... connecting the LDR directly to the top of the audio gain control dropped the audio level noticeably with no signal present, so I also added a series resistor, but only about 2k2.
I used a high intensity white LED and a 4k-40k LDR, links in the blog post. ?I'm pleased with this circuit and will use it again. ?
73 from Paul VK3HN.?
VK3HN