Jerry,
Yes, that's the RF preamp.? What really happened is that I just wanted a hot receiver, plain and simple. No excuse, no glory, just that I wanted to pick up almost anything on a string of wire for demo purposes or for field use.? Regardless of reason for it, the perception of attack and decay seem to be controlled by the traditional AGC board output (that is, the S-Meter output), as it would be after all since the traditional AGC is just before the radio's front end stuff.?
To simplify: If the latter's initial reaction to a heap of a signal were to show a high S-meter reading [had I been using the S-meter output to run an S-meter], then the former (the preamp) is going to be put on speed brake to lower what gets sent past it; I'd assume that the latter (the AGC) will immediately perceive less signal shoved into its face and will relax at whatever normal, preset recovery has been programmed.? I don't see the two fighting against each other, so, there is that bit of success.
As to which ND6T circuit i have, I've got a kit version sent to me by the same fellow who solld me a V3 board near the end of winter this year, and, I've got an SMD version right from the maker's.? Both of my uBitx radios are using this preamp/AGC combo, one with the home-wired AGC and t'other with the ready-made SMD board.? It just so happens that when a strong signal comes rolling in over a weak one, two devices are getting instruction to reduce flow. My addition partially shorts out the RX path, while the normal or ND6T type AGC "fails to pass" as much signal as it did a moment earlier. The result is the same either way, and, I'm doing both (once each in two radios) and it's fine.? Overkill, but doing fine....
Here's the hook-up, simple enough:
At first - when I had the preamp and no AGC controller at all, I did use a 386-based amp board from somewhere or another to provide the control signal.? This setup seems to only needs about 0.7v on the gate of the 2N7000 to make at least some difference; at about .8-.9v, incoming gain is subjectively reduced to just under unity/without preamp levels and at around 1.2v on the gate the radio is deaf as a post.? If operating with another AGC, it's fine that way; operating without one, I expect that I'd want the 386 back? so that the RF preamp would function better as a one-piece combination.
Ted