Let's take a simple, low cost radio, the QYT CB-27. Sold on most platforms as a Citizens Band radio, the radio has within its processor the ability to do 10 meter FM, as well as a full VFO operation in AM or FM from about 25 MHz to 30 MHz. It would be nice to narrow band the FM portion this radio as well.
A Chinese ham commented on a board that he did a few mods access the 15/12 meter band, but he had docs which were "non-English". He did not respond to English or German posts on the method undertaken to achieve this, so it's assumed the docs were in Chinese only.
Another mod which would be nice to do is the ability to send CW with the radio receiving via an outboard DSP. The PTT of the radio would be clumsy, and not suitable for anything over 12wpm. But there are usually taps you can take with a delay circuit for the RX to convert a radio properly.
And if you want to get real geeky there are voice inversion mods which are done with ease in the ICOM, Motorola, Vertex/Yaesu, and Kenwood world. But to do them right, one needs to know points within the radio to tap.
On a simpler front, the radio would be super for packet transmissions in remote locations, since it is low power and low current draw. However, the audio circuit of the transmitter has too many issues to provide a clean audio bandpass without phase shifting. A better injection point is required to transmit without causing distortion to the data stream.
So, what the radio brings to the table is a lot of cool experimentation for a real cheap price. But it's thwarted by not having a good set of English docs. And the way the radio is made, I doubt someone could get far by circuit tracing.
There are other radios which show promise. BUT, you need good documentation to even plan a modification. I've done a fair amount of mode to both manufactured radios as well as broadcast equipment turned ham. The key is knowing what is there and how to manipulate it.
73
Fred
The one thing I despise about Chinese radios, is the lack of schematic, service manual, or necessary technical documentation. There are several radiosw which are good candidates for usable modifications, but with no docs it's impossible to do.
What would those “usable modifications” be?