This is what I have found,I don't know if it will work on the 242 and almost positive it will not work on the 212:
Modification for a Radio Shack HTX-242
« Thread started on: Aug 4th, 2002, 3:25pm »
Posted by Jeff Parrish (KB9GXK) on September 11, 1998
Special NOTICE: This is for the HAMS who say radio shack radio's are "can't be
modified, because the FCC was real strict with Radio Shack", or buy a real radio so
that you can modify it. That is a bunch of bull.
Mod: Expands TX from 143-149mhz to 136-174mhz
Tools Required: Phillips Screwdriver, Mini screwdriver, Soldering Iron (Fine tip) ,
NeedleNose Pliers
Process:
1.Remove Screws on bottom and top 2.
2.Take the Bottom and Top off the Radio.
3.Unplug Speaker from top of the radio and remove the dials from the face
plate.
4.Unscrew the screws on the top and bottom of the face plate.
5.CAREFULLY: remove the face plate from the radio.
6.Remove the bolts and washers (little rings) from the dials (countersunk into the
dials).
7.CAREFULLY: remove the LCD and plastic around it by pulling gentle and
wiggling it a little being careful not to bend the LCD pins.
8.Remove the screws holding down the PCB from the cases.
9.CAREFULLY: (Plug in type PCB) remove the PCB from the radio and place
the VFO tuning dial face down and to your left.
10.There will be two blue jumper mounts on the PCB. Remove the 1 closest to
the 2 black raised chips that are closest to the VFO tuning dial (this jumper
should be near the middle of the board) The other jumper makes the
transmitter do 143-144 (military) and it is near the side.
11.Put all the parts back together and blamo you have 136-174mhz RX/TX
Notes: If you do it right you won't even loose your memories. This mod took me
about 30 minutes to complete and my radio is working fine. However I'm sure this
voids the warranty and the service contracts so you may not want to do it for that
reason alone. I checked the radio out (with a frequency counter) on several
frequencies and it is performing well. This mod requires a little skill but most people
that are hams could do this mod. This mod was given to me by a fellow North
Carolinian KC4VYY , and I just put it in a simpler form.
I wanted to thank him.