Hello,

I am trying to design and develop a long range portable transmitter.

When I say long range I am talking open distances between 5 km and 10
km radius where a receiver is established at the highest center point
within this radius and also elevated using a 20 meter antenna.

Ideally the transmitter will 'send' a three digit numeric code, such
as 101 or 102.

I have researched existing products and have found one of the VHF
variety which would satisfy my requirements however it is exspensive
and not exactly of the 'portable' variety.

What I am looking for is suggestions on existing products or designs
that could be used to acheive my requirements.


Thank you.