IW4AJR Loris <lorisbollina@...>
From my tests and from the measurements made, it appears to me that the best known "AGC" modification module is a very bad "ATTENUATOR" placed in series with the receiving antenna!
Although I have tried, measured and studied the scheme and compared it with the reality installed on my µBITX-V6, the theory of the principle used confirms what the practice shows:
Although an automatic attenuator placed in series with the antenna is excellent (try it yourself with the best PIN attenuators on the market) the residual attenuation of the circuit at the minimum attenuation will never be less than -3dB, often, even in the most refined circuits. , yes it gets a minimum of -5 / -6 dB! ... not to mention what two poor quality MOSFETs can do (compared to a PIN diode attenuator) ... the best measurement I got was -10 / -15 dB, which is equivalent to losing at least 2 S points on the reception!
It is totally unacceptable! and technically from "geeks" and not from radio amateurs!
From my tests, only one module acts correctly on the "gain" of the MF amplification and, even if a bit obsolete and bulky (it is not built in SMD), it would seem the most efficient module, not changing the "sensitivity" of the receiver (very important thing in DX also in QRP).
Why do you insist on referring to these "ATTENUATORS" as "AGC" "Automatic GAIN Control"?