Why to decrease the microphone level using resistors and after again to boost the signal?
Poor signal / noise ratio of TX modulation - modification.
Other pics during front panel programming: Group 1 - Channel 1, rX Frequency (PMR CH-1).
Immediately i saw some resistors between microphone connector and preamplifier stage.Final result: improved TX modulation, close to Motorola quality.Realignament / tuning of radio can be done by PC software or using Front Panel keys.Good results but level of modulation was affected.Adjustment - page.This resistor is located on front panel PCB, near to CPU.Keep pressed call key, in same time switch ON the radio.All dividers were removed in order to increase the original level of modulation: R512(680) removed; R724(4K7) bypassed; R725(15K) removed (resistors values found in my radio, not same with Service Manual.Next steps can be easily understood.IC preamplifier is located on Front Panel PCB.Connect data cable and go to KPG-60D PC software at Edit / Channel Information.In order to activate the feature, R614 "zero ohm" resistor must to be deleted!
"self programming" option can be accessed.
Frequency accuracy, modulation deviation, TX power, RX sensitivity and other options are available.
After investigation, IC711 microphone preamplifier was found with poor perfomances.
I tried to apply 1nF roll off capacitor in the feedback loop.
Please check SM diagram).During testing I noticed a low signal to noise ratio for.Keep pressed B key, in same time switch ON the radio.Check the service manual for more details.Channels programming procedure can be performed by PC software or using Front Panel keys.Radio display when internal CPU is accessed by computer: - Front panel programming is possible only if "Self Programming Mode" option was previously selected by PC software (go to Edit / Option Feature and then upload to radio).Feedback R721(330K) line 6 jm4 looper manual pdf resistors was replaced by 100K.Connect data cable and go to Program / Test Mode.
Kenwood TK-880, pC Software programming for TK-880: KPG-60D Serial cable between PC and Radio: Programming Interface KPG-46 Schematic TK-880 Service Manual rev.