There has been a bit of BITX20 IO Groups list chatter about the winner in ND6T’s AGC circuit (with RF gain control).
Ion VA3NOI has two versions of an ND6T AGC circuit board designed.
- A through-hole single-side version measuring 17X38 mm.
- An SMT board measuring 18X31 mm, with SMT components that are 0805 in size.
The . 1 uF cap is tantalum or niobium polarized.
The design was done using Eagle 7.5 freeware. The zip file in the Gerbers Folders should be uploaded to the PCB manufacturing house.
The boards are roughly 1 square inch in surface. You can place 10 boards on a 100X100 mm panel and get 10 panels for $5 plus shipping. For making into a kit, Ian recommends the SMT version as it will be more affordable and he expects it to have better performance on the upper bands.
He has ordered a through-hole version for experimenting with some values (AGC release time minimum resistor and coupling capacitors on RF line) and this is en route to Canada.
The PCBs have provision for adding a pot to adjust AGC release time and a switch to disable the AGC. Ion has posted the files (schematic, board layout and Gerbers) here:
Constructors should feel free to use the files as they see fit. He is also happy for anyone wanting to put kits together.
Kees K5BCQ is looking into whether it can be sold as a kit through his website.