I am working on an VHF down-converter using the SA602. The RF input impedance to this chip is 1.5 kΩ. I understand that hooking up to most antennas will require a 50 Ω matching network. However, for this case I am wondering if I need a matching network at all.
Matching is to avoid losses from reflection. I am Using the equation line length/wavelenth > 0.01, so any line length ratio to wavelength ratio larger than 0.01 will have reflections.
At 140 MHz, if I keep the trace length to the antenna connection shorter than 1 inch, then transmission line effects can be ignored, correct?
Even assuming a short transmission line, do I still need to design the antenna to have 1.5 kΩ impedance to satisfy the maximum power transfer theorem? Or would any antenna (receive only) be fine so long as it is tuned for 140 MHz?
Edit: To sum this up, I can design the antenna with 1.5 kΩ to match the IC input impedance of 1.5 kΩ. I understand 50 Ω would be needed if I were using a 50 coax or stripline, but the trace is around 1 inch. The antenna connection would be direct, no SMA or BNC (since those are 50 Ω).
I wanted to bounce this idea of off some RF gurus out there.