[Discuss-gnuradio] dual-gate mosfet front end - results

[Chuck Swiger]

Gang - just for the record this front end:

http://www.designnotes.com/CIRCUITS/Activeantenna1.gif

works at least as good as, if not better than the MPF102 version (but w/o the
tuned input, just using a capacitance coupling to the antenna and 1.5Mohm from
gate to gnd). Using a long random wire, tuner, the above circuit, a passive 
bandpass
filter then the usrp, I get this spectrum:

http://webpages.charter.net/cswiger/ssb_80m_2.jpg

the overall peak around 3.9mhz is largely a function of the tuner, easily moved
wherever you want. While watching the spectrum, recorded around sunset Mar. 6,
it's easy to see something 'sweeping' the band every so often. Also there's
a curious emission just under 4Mhz, a wide block of hiss from 3995 to 4000k.
In audio it's just a hiss. Any guesses? Amateur DRM?

--Chuck