ND6T sort of mini AGC ?

Adrien F4IJA

I've found this from ND6T :

On his website, we can find lot of ther AGC schems for ubitx but I wonder what is the usage for this very simple circuit ?
By reading the article, it seems that it cuts off too strong signals, so the annoying "clacks" should be canceled.

Do you think, if you don't plan to add a real AGC that this mod is a good idea for securing ears ?

As I'm a newbie with AGC : what are the benefits of having an AGC in ubitx ? I've well understood than the too heavy sounds will be reduced, but what else ?

Thank you,

Don, ND6T

Hello Adrien,
That is not an AGC circuit, but is just a limiter circuit. No "clack" elimination but it does limit how strong it appears in your ears. It is hearing protection. I have installed that in several of my shack speakers. Since I do not like the sound of the small speakers in any of my rigs then I always use a larger, more efficient speaker whenever I can. To keep things simple then I install headphone jacks within those speaker enclosures (just one wire from the receiver). It makes sense to put a headphone jack on that speaker cabinet and a switch. The added limiter is a welcome feature to my ears.
The AGC circuits that are found in the uBITX and BITX pages are to confine the SSB signals to conversation levels. Without it, the weak signals are very quiet and the strong signals can be too loud. The AGC circuit helps keep them within a comfortable range without distortion and without constant adjustment.
The "clacks" when changing from receive to transmit (and back) in BITX40 and earlier versions of the uBITX can be nearly eliminated by installing the circuit described in the "ClickFix" pages in both the BITX and uBITX pages.
Does this answer your questions? I can be best reached directly by email, either from my web site or from the address on
73, Don

Adrien F4IJA

Hi Don,
Thank you for your answer, directly from the maker ;-)

OK well I understand what you're saying and the differences beetween.

Well noted the PopFix page I've found on too.

I think I'll take a lool to AGC kits sooner as lot of people do.

Adrien F4IJA

Doug W

There is so much information on this list that sometimes it is like trying to drink water from a fire hose.  If you access the list from there is a search function that is helpful when looking for specific information.  There are many discussions of AGC circuits including ND6T's great designs.