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RDF Base Station Antenna prototype


Jon - KI6RT
 

RDF Base Station Antenna prototype for discussion. 
The proto shown is not using final PCBs (out for fabrication). Whips shown using copper wire (pulled off of scrap Romex) not stainless steel nor telescopic elements. But it solved the primary problem -- eliminates hassle of setting up the antenna to test/evaluate the RDF Doppler electronics.  

Link to full document below. Comments welcome.
https://w6ek.groups.io/g/sfarc/files/RDF%20Project%20Files/base%20station%20antenna.pdf


Jon - KI6RT
 

For EEs that have run out of things to read...
https://w6ek.groups.io/g/sfarc/files/RDF%20Project%20Files/base%20station%20electronics.pdf

Any inputs/refinements to the RDF electronics? 
  • I usually put a Nano footprint on the board so that a Nano can just be plugged in. Should it be shield instead?
  • I used a 555 as a DC/DC voltage inverter to generate -12V. Why not an LDO? Cost. The 555 circuit is cheaper.
  • Not sure a LP filter is needed. I wanted some type of buffer for the audio therefore rather than a unity gain buffer decided might as well make it a Sallen-Key LP with an Fc of around 700 Hz.
  • Integrator to shape antenna pulses -- with the slow rise time there should be no need for a PIN diode. Thoughts?
  • Have made no attempts to separate ground domains (rf, digital, analog). Should we separate ground domains and place mecca ground at the DC input? I think not critical but...
Anyone have their CNC setup to route PCBs? I damaged stepper motor on mine so need to fix. If you have such a capability let me know & I'll send over the Geber and PCB blank.

Thanks in advance for your inputs.

Jon