Hardware Hacking

On the RadioShack HTX-252, the squelch takes a fairly long time
to open, so much so that the first few syllables in a transmission
are often lost. I modified my rig to shorten this time constant
by removing a chip capacitor. The location of this part is shown
in the picture, it is just in front of the transistor in the
highlighted circle in the diagram on the bottom of the rig.
The value printed on it is 105, I assume this means 1mfd.
The picture shows the capacitor already removed. You can see the
silkscreen on the board that was previously under the capacitor.
Now the sqelch snaps open almost immediately when a signal appears.

Steady hands, some solder wick, a pair of tweezers and a small
tipped soldering iron does the trick. It’s a surface mount capacitor.

I wanted to pass along the following information that I discovered
regarding increasing the audio level on the Radio Shack HTX-252
2M radio. This is apparently a common problem with this radio and
I was not able to find any existing mods for fixing it - so I decided
to try for myself.

Remove the four screws holding the top chassis cover (which has
the speaker grill) and remove it. The speaker is conected by a long
enough pair of wires that removing it should not be necessary. If
removal is necessary it is held in place by four screws which are
easily removed.

With the front of the radio facing toward you locate the variable
resistor labled RV2 which is located almost dead center on the
main circuit board.

Turning this variable resistor clockwise will increase the deviation
and raise the audio level of the transmissions. Be careful not to
increase the deviation too much.

After making this mod to my radio I have been receiving reports
that my audio is 100% better, and is at a level on par with everyone
else.

Good Luck
Rick
W2RDS

Start by removing the 6 screws which hold the case together.

Remove the channel and volume knobs.

Remove the nuts which hold the antenna and volume/channel controls.

Unsolder the speaker leads.

Carefully remove the chassis from the case.

Remove the 2 gold colored screws which hold the smaller board to the main
board.

Unplug the smaller board from the main board and set it aside.

Looking at the main board, there is a uP IC ( large black chip) at the
top.

Near the upper right-hand corner of this IC are 2 vertically oriented
solder jumpers and one just to the right of them which is horizontal.

To open wide band TX/RX, open the vertical jumper nearest the IC and the
horizontal jumper.

Reassemble the radio.

Hold the function key (F) on the side of the radio, the ‘6′ key and the
‘MR’ key while powering the radio on.

All memories will be cleared and the radio will be ready for wide band
programming. In addition, the ‘BAND’ function will no longer go to
preprogrammed weather channels.

Beyond MARS/CAP Mod
To do MARS/CAP mod on your HTX-200/400 turn off the power.
Turn on the power while holding the SC button.
The new TX coverage will be displayed.
Does not always work the first time.
Can be reversed in the same manner.

Beyond MARS/CAP Mod

Remove the top and bottom covers, also remove the 3 control knobs
Remove the 2 screws holding the face of the radio, and remove the face.
Remove the 3 nuts recessed around the control pots and gently remove the LCD assembly
Remove the 3 screws attching the remaining PCB to the chassis of the radio.
We will be working on the backside of this last board
There are 3 frequency ranges to choose from.
The 144-148 MHz FCC band (Already installed)

The 144-146 MHz European band.
The 136-174 MHz US Emergency Services/business band
Remove one of the two parts shown below. BUT DO NOT REMOVE BOTH