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FT-817 AGC modification | Radioaficion Ham Radio

FT-817 AGC modification


Yaesu FT-817 AGC modification

Regarding the AGC (RX) of the FT817 I got some questions from some users. The dynamic of the AGC-regulation isn´t really nice researched. If you use the rig specially on 40m and/or 80m where often high signal strenths are present, the RX sounds like the AGC is switched completely "off". If using with small signal amplitudes it sounds much better. This seems to be a general problem of the FT817.

To fix this is only recommened for let me call it "advanced users". The rig has to be opended on the upper side (where the loudspeaker fits). Now you remove all connected cables from the visible main board and all srews. After this you can remove the board.

Please turn the board to the soldered side and locate C1324, which is nearest to the connected data-cable going to the user-interface (front panel).

Near this C you find R1305. Original values are 1 K and 2,2uF.

Now the mod:

Please put 10 Ohms in parallel with R1305 and 10uF parallel to C1324.

Please be carefull in doing this, the SMD-parts are very small !

In my case, I had no SMD-C available (and I didn´t want to use Tantal-C´s), therefor I connected the 10uF via cable to the upper side of the main board. It´s not looking nice, but nevertheless it´s working.
Values over 10uF (470uF) are better, but the S-meter stand still at approx. S6-7 afterwards. It´s not recommended to go over 10uF.

Good luck and again: be carefull!!!

FT-817 AGC modification

FT-817 AGC modification

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