I acquired one of these scanners several years after they were introduced. It covers about 60 MHz to about 900 MHz continuously. It is not a serious receiver and I will refer to it as a scanner. It does operate on AM, FM and according to the manual SSB up to about 450 MHz. Apparently it is one of YAESU’s first units that could be computer controlled.
The operation of this scanner seems to me to be a bit odd. For example, in the AM mode it assumes 5 kHz steps although it can be programmed to 100 Hz resolution. You cannot tune the dial in 1 kHz or 100 Hz steps. It can be set up in a narrow and wide bandwidth mode for AM. A problem is that the wide mode is not all that wide and the narrow mode seems about useless. If a station is not on frequency, assuming it is suppose to fall in one of the 5 kHz steps, turning the dial one step will put you either 5 kHz higher or lower from the previous frequency. If the station you want to listen to is in between, it will likely sound distorted. I use the AM mode mostly to listen to aircraft frequencies and occasionally an aircraft transmitter will be off frequency. It appears that the radios used by the air traffic controllers are wider than this scanner or they certainly don’t complain much.
The scanner has good sensitivity on VHF although it does suffer from intermod. Image rejection is good, unlike the PRO-2026 shown elsewhere on this website. I have checked the sensitivity on UHF and it varies over the band but generally it is not great. Two microvolts for 12 dBs is not unusual. I have not measure it around 900 MHz but I suspect it is even worse. The sensitivity of the PRO-2026 is generally better.
The FRG-9600 uses a bar graph to indicate relative signal strength. I sometimes preferred an analogue readout when comparing two or more signal so I put together some circuitry and installed it with a meter in a plastic box, nothing very fancy. This scanner has a dc output for this purpose on the back as indicated in the operating manual. When I measured the voltage referenced to ground it sat at about +4.6 VDC with no signal and drops to about +2.6 VDC with a strong signal. I used a general purpose op amp configured as an inverter to convert the levels. I later found a service manual for this scanner on the internet and it referred to the level as going from 0 volts with no signal to about +2.5 volts with a strong signal. From what I can tell this voltage is referenced to the busy output indicator on the same connector but neither manual mention this.