Yes I Can
Without the aid of a photo here I will do my best to describe this....
Also folks, DO NOT ATTEMPT THIS IF YOU ARE NOT ELECTRONICALY/TECHNICALY SAVVY for you may regret it!Being very serious here now!!! Also I can NOT be held responsible for ANYONE who makes a mistake,you will endeavor this MOD at your OWN RISK.
Now - all that said and done......... here goes..............
First disconect the radio from all power sources and antennas and external speakers and what-not also disconect the MICROPHONE.
Remove the 4 screws that hold the cover on the radio(the cover that does NOT have the speaker on it,the OTHER blank cover)
once that is removed you will be staring directly at the circuit board with IC's on it.Place the screws and cover in a safe place and don't lose them.
Now take the radio and look directly at the MIC JACK with the circuit board side UP.You will see the pins of the MIC jack line up with the solder connections for them on the circuit board,the pin with the base band audio from the discriminator will be here in the TWO sets (rows)of MIC JACK pins soldered on the circuit board,Three pins are in each row for a total of six pins,the base band audio pin is the FIRST pin on the LEFT of the FIRST ROW closest to the edge of the circuit board when you view it as stated above.That was where I soldered the center wire of a THIN audio cable to and I attached the shield (Ground side of the cable)to the screw directly in back of the solder connections for the MIC JACK(Other shade tree techs may opt for another ground point ,thats cool!).Be aware there is ZERO and I mean it cause this is a MICRO RADIO,,,there is ZERO room to work and a lot of margin for ERROR here so BE VERY CAREFUL when attempting this.So I then routed the cable(it is very thin audio cable)along the side of the circuit board and out towards the rear of the radio and exited out where the rubber gasket holds the DC power wires in place,and it came out very nicely.The end of the audio cable that exits the radio I cut and left about a half foot or so and attached a Female RCA Audio connector to it so I did not have to coil up any cable when I transport the rig from home to car and vice versa.Once the cable was soldered in and I was confident that my work was clean and finished and the cable was routed (I opted to TAC down the cable inside the radio with a couple of micro dots of EPOXY to the circuit board for stability) I very carefully hooked the power to the radio and an antenna and ran the audio connection to my laptop MIC input ,booted up T4W, tuned in the 800mhz type II control freq and SON OF A GUN IT WORKED !!!!first time!!COOL!Now after this I disconnected everything and carefully placed the cover back on the radio and secured it with the four screws plugged the MIC back in the jack,and declaired "Its MILLER TIME"!!! So basically that was how I did it,as I said others may opt for variations on this but THAT PIN is where you will get the JOY of the BASE BAND AUDIO from the DISCRIMINATOR out of the mic jack on this radio.It was provided there for by Yaesu for PACKET RADIO hookups and the MOD will not affect the performance of this FT90R at all, The Dual band rig works great on the ham bands and the MOD works fantastic for the application in the use of T4W!Take care - BE aware! and ENJOY!!!
73!
Robert-KA2MEK
General Class Amatuer Radio Operator
Middletown Twp,NJ
