There are existing plans to extend the RECEPTION range of the CM15a. I have built an external antenna and can recieve up to about 150-175' away which is common for those who modify and add antennas.
There are two mods that are common:
1) extend the internal antanna cable and re-tune it by extending the internal wiring to it's maximum length and keeping it straight with a straw (don't laugh) or external metal tube. These get about 40-60' I hear.
2) Add components to extend and add an antenna using 50 ohm coax and a hand-built "x-style" twin-lead antenna. You can place it centrally located in your house. I did this in the center of the basement.
This is a picture/plan for the antenna I made:
http://www.shed.com/tutor/mr26ant.htmlRemember, this mod requires 50ohm components.
Search these forums for "cm15a antenna" posts or google for cm15a antenna modes if your interested. There should be a few.
There is also talk about TRANSMIT antenna plans but no concrete plans I have located to date due to the complexity of tuning (remember tuning CB tuning standing waves?).
Eric Edberg