This was made to give it a little directional bias, and indeed, it transmitted very directionally, boosting its range to several kilometers in free space.
Our intention, as a small startup company, to sell this as a finished kit, or do-it-yourself kit. In those days, people were tending to copy any transmitter design and claim as their own. So, we made a tricky decision. In the PCB, I changed the dimension of the three coils so that they mimic something like our company name ‘RCL’. See the PCB design below:
For the sake of this particular transmitter, consider the special design of coil now just mearly a coil; and does in no way represent any company or company name.
This actual design was made using a very early version of ‘Protel‘, called ‘Protel 99SE’. I designed this on a 486 desktop having just 4MB RAM and a 256KB video RAM. Today when I see this, I find myself that, to create brilliant things, we may always not need the latest gadgets and software.
Because, this first design, and all subsequent improvement of this version (that I designed on the same computer using same software), was best-seller for our company back then.
So after selling many thousand units of this transmitter across the globe, the design has been retired and I decided to offer this for free to the internet community and posted that to ‘Tripod’.