Re: [Discuss-gnuradio] lfrx+loop antenna

[Eric A. Cottrell]

konvak wrote:
> hello all, 
>               I am thinking about building loop antenna for 3-6 MHz to
> receive some DRM stations. As I understand it the loop antenna is parallel
> resonant circuit so without any amplifier the parallel res. circuit should
> look into big impedance(~1 MOhm) to get high Q. Lfrx has 50 Ohm input due to
> the resistor at diff. amplifier. My question is, would it be possible to
> remove this resistor and put there 1MOhm and connect it to the loop antenna
> with coax. Would it work?
> 
> thank you for any suggestions and help, 
> tomas
Hello,

I have seen both buffer amplifiers and toroidal transformers used for
loops.  Be aware that loops have low signal output compared to other
antennas and the signal advantage is the noise pickup is lower (higher
S/N rather than higher output.  So some gain is needed to connected it
to the Lfrx.

I had good sucess with a KAZ antenna, which is a triangle that is 40
feet long and 10 feet high.  It uses a 9:1 toroid matching transformer.
 It is meant for LW and MW but seems to be okay for low HF.  I used my
usrp connected up to the 10.7 output of a receiver rather than connected
directly to the antenna.

73 Eric