AGC-controlled Termination Insensitive Amplifier experiment

The Termination Insensitive Amplifier (TIA) is a popular wide-band RF and IF amplifier, and a foundation of the Bitx, uBitx and many other superhet radios. A minor draw-back is its fixed gain. In this video, I experiment with a mechanism (proposed by George VK4AMG) to add AGC to a TIA IF amplifier stage. The mechanism varies emitter degeneration and is similar to a scheme using PIN diodes shown in EMRFD Fig 6.41 (which is not a TIA). This mechanism works, but there are side effects. Is it a useful hack? Tell me what you think! Thanks to George VK4AMG, Bill N2CQR and Peter N6QW for helpful comments and feedback. 'A Termination Insensitive Amplifier for Bidirectional Transceivers', Wes Hayward, w7zoi, and Bob Kopski, k3nhi. © 26 June 09: http://w7zoi.net/bidirectional_matche... Facebook (VK Homebrew), scroll down to George VK4AMG's post, March 3rd 2021:   / 1689037384702683   Blog post: https://vk3hn.wordpress.com/category/... Disclaimer: I am not an RF design engineer and I offer this as an interesting experiment to home builders and experimenters. If you want to challenge or debate the approach, I encourage you to model, build, measure and report your findings!