"Marcus Tait" wrote in message
...
I have been designing a small transmitter on 400MHz. The output from the rf
amp is a parallel LC tank and between the collecter and +V. When measuring
the output on a specturm analyser i can get most output when centre tapped
on the inductor. The output must then be matched to 50ohm as the spectrum
analysers input is 50ohm. The anatenna for this transmitter is just going
to be a 1/4 wave piece of wire. My question is that as i dont need to send
the signal down any 50ohm cable could i just connect the antenna at the
collector rather than tapping onto the inductor and then adjust the length
of the antenna to increase its inpedance to match the output inpedance of
the transmitter.

I would take a look at how remote garage door openers are configured. They
operate in roughly your frequency range. Mine has a range of about 100 feet.
A 1/4 wave antenna has an input impedance of 37 Ohms, but I suspect you will
not want to do that.

Tam

Tam