Rtl-sdr HF LNA

What is RTL-SDR

DVB-T dongles based on the Realtek RTL2832U can be used as a cheap SDR, since the chip allows transferring the raw I/Q samples to the host, which is officially used for DAB/DAB+/FM demodulation. The possibility of this has been discovered by the V4L/DVB kernel developer Antti Palosaari.

High Frequency (0-30Mhz) Direct Sampling Mod

Steve Markgraf of Osmocom has created an experimental software and hardware modification to receive 0-30Mhz directly by using aliasing to do the conversion. In the stereotypical ezcap boards you can test this by connecting an appropriately long wire antenna to the right side of capacitor 17 (on EzTV668 1.1, at least) that goes to pin 1 of the RTL2832U. That's the one by the dot on the chip surface. Apparently even pressing a wet finger onto the capacitor can pick up strong AM stations. This bypasses static protection among other things so there's a chance of destroying your dongle. - http://superkuh.com/rtlsdr.html

Notes

• Balun (1:4 for 50Ω antenna?)
• Differenital input impedance ~ 200Ω
• R820T output impedance 2kΩ
• Max input level +7dBm
• Output level of R820T tuner 1Vp-p
• J310 FET (gain?)
• Internal sampling rate 28.8Ms/s
• Max frequency with direct sampling 14.4Ms/s (Nyquist)
• <14.4Ms/s physical LPF (order?)