Re: Audio AVC

Jerry Gaffke
 

Ted,

I assume it's this RF Amp from kitsandparts for $12:  http://www.partsandkits.com/rfamp1.3.php
Not a bad idea if you have a compromise antenna such that you don't hear band noise when the antenna
is hooked up to the radio, especially on the upper bands.
Though such an antenna may not be very effective for getting out with the transmitter.

Do you have the ND6T AGC circuit with the added series element: http://www.nd6t.com/uBITX/AGC.htm
 (A kit is available from https://shop.kit-projects.com/ )
Did you find that it didn't have enough dynamic range?

Perhaps you have the earlier ND6T AGC circuit:  http://www.nd6t.com/bitx/AGC
and thus needed the extra AGC circuit.

> The preamp 1st stage has about no delay while the 2nd is on a medium-fast timing.

So "no delay" means very fast attack and very fast decay?
I would not expect that to work very well with an SSB signal.
Did you add an extra LM386 just to sense the audio to drive this extra AGC attenuator?

A schematic would be interesting!

Jerry, KE7ER


On Sun, Apr 21, 2019 at 05:19 AM, Ted wrote:
For what it's worth, I present here the Crowbar Method. It incorporates the best of a quest for maximum sensitivity along with absolute overload protection.  It began when I saw a post here for a sideband RF preamp from partsandkits, an item that I've added to both ubitx projects here.  My first stage of AGC begins with that board.

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