Hello Geoff,

Thank you for your response.

Is this for licensed or unlicensed operation?

Eventually licensed.

Is this a "one off" unit, or do you plan to make
5? 10? 1,000? sell them to everyone on the planet?

I plan to replicate approximately 10 to 15 transmitter units and one
receiver. This project is for a volunteer organisation.

What do you mean by the word portable?

When I said portable, I was referring to it being independant of an
external power source or external mounted ariel. It's ideal size would
be similar to that of a book, preferably a cellular phone, however
cost is the main consideration.

Will it provide it's own power?

Yes.

How long will it need to run?

There is no operating time requirement, the only time related
requirement is that the power source lasts long enough to transmit a
simple message.

How? CW (switched carrier?) MCW (modulated switched carrier?)
Voice (AM? FM? SSB?), some sort of digital modulation?

I was thinking AM or FM however CW is an option.

Whichever is the cheapest component wise and irrespective of the power
requirements, is portable and can transmit at the desired range of 5
km to 10 km.