Re: [Discuss-gnuradio] Active Radar Hardware

[Jason Hecker]

> We make MF & VHF systems and for some of our VHF systems we use a single
> set of antennas and a T/R switch (passive and active). However since our
> frequency of operation is 2-3 orders of magnitude lower it's probably all
> different...

The radar I worked on was a ~2.7GHz job.  Since the receiver was spammed for 
the first several hundred metres in range due to large amounts of echo from 
ground clutter any such early returns were gated out.  After that the circuit 
controlling the attenuator (PIN diodes) ramped the voltage so that the 
overall gain of the system increased in time.  This was to maximise or 
normalise the S/N ratio at the ADC.  When you are looking for metallic 
bogie's many 10's of KM away you need all the return you can get even with 
the gain achieved from integrating multiple returns.

Anyway, the author of the grandfather post doesn't sound like he has too much 
RF experience (who does?)  Perhaps a circulator will do or even better, an 
RX/TX switch module (diplexers?) - though this might involve a hardware hack 
to get the switching pulse out in time.  The thought did occur to me to get 
something like a Furuno boating radar head with an integrated separate 
transmit and receive antenna.  You'd get a nice narrow beam from one of 
those.