Cobra 87 / 89 GTL an President Zachary T MOSFET

[Pizzaman247]

Ok - This is tested an proven on my own radio an give a serious improvement over the stock 2sc2029 final - First replace the final with an IFR520 mosfet - Remove R44 - R48 - C55 then replace R48 with a companion part made with a 1N4148 diode an a 470ohm resistor - Add a 68 pf cap across C53 - Remove slug from final tuning coil - Reduce R49 ( 4.7 ohm ) by about 50% - Spread coil L11 slightly

My 87 GTL keyed at 6 watts with PEP of about 18 watts ( Stock ) - This conversion keyed 3 watts an has PEP of about 27 watts - Test was done with a PDC600 meter ran into a Drake dummy load

[Grinder74]

How's that look on a scope?

[Pizzaman247]

It was actually very clean unless you pushed it too hard with a power microphone - The key is to leave the limiter intact an set it about dead center on the the VR adjustment