Microphone Response HTX 100

Mon, 06 Apr 2009 15:57:00 -0400

Enhancement of Microphone Frequency Response

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Remove top cover of the radio and with the display facing you and the radio
upright locate IC3 (MJM45585) near the bottom right hand corner of the main
large board.

Just to the right of this IC locate c75 (56 pf) and remove it. This will
increase the gain of the microphone Preamp considerably but without
overmodulation.

Microphone contacts Realistic HTX 100

Mon, 06 Apr 2009 15:54:00 -0400

Microphone contacts Realistic HTX 100

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Pin 1 = Microphone input

Pin 2* = Push to talk

Pin 3* = Scan down

Pin 4* = Scan up

Pin 5 = 8 Volts

Pin 6 = Audio out

Pin 7 = Microphone Ground

Pin 8 = Ground

* NOTE - Connect these pins to ground for function to work

Extention frequency mod Realistic HTX 100

Mon, 06 Apr 2009 09:14:00 -0400

The Realistis HTX 100 radio was also produced under Tandy and Uniden

Frequency extention mod, from 26-30 Mhz (normal 28-30)

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-Remove Power and Antenna.
-Remove screws and open the case.
-Locate synthesizer board on the bottom of the radio.

-If your radio has microprocessor # UC-1208 Unsolder and lift pins 28 & 29 of the microprocessor.
You may wish to leave the pin soldered and etch the ground trace. Go to instruction #

-If your radio's microprocessor is NOT a UC-1208 Unsolder and lift pins 20 & 21 of the microprocessor.
You may wish to leave the pin soldered and etch the ground trace Go to instruction #

#Connect the lifted pins together and jumper these pins to +5 volts through a 10K resistor
(+5 volts can be found on the 7805 voltage regulator or from the Cap. right next to pins 28 & 29.)

-Reassemble the radio.

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This is the mod that can be found around the internet, this this not work for me with the UC 1208. Try not to bent the legs of the processor they will break. So you need to unsolder as much of the solder of the pins that you can get off. Then direct after the pins from the processor cut the double trace. This will go a little stung because off the solder. (you need to do it direct after the 2,5 mm pins; 3 mm of the pins is a ground point thru the board).

Pin 28 & 29 is the 4 and 5 pin on the right side from above

Then get the dialling knob off (just pulling) you will see a small hole with wire on the ground of the hole, connect the wire against the chassis(this is a compleet reset)).

Than power it up...

Mods Blog

Microphone Response HTX 100

Microphone contacts Realistic HTX 100

Extention frequency mod Realistic HTX 100