Search found 102 matches

by hotpaw2
Wed Feb 20, 2019 12:54 am
Forum: User Projects
Topic: How exactly are the IQ channels supposed to be calculated/processed?
Replies: 2
Views: 6798

Re: How exactly are the IQ channels supposed to be calculated/processed?

Note that: (x+iy)*(x-iy) = x^2 + y^2 so a * (cos(w) + i*sin(w)) * (cos(w) - i*sin(w)) = a * (cos(w)^2 + sin(w)^2) = a * 1 = a where w = 2 * pi * f * t Both e^iw and e^-iw are used to get e^0, which leaves the original RF signal unchanged. Note that simple multiplication can be used for the first het...
by hotpaw2
Fri Feb 01, 2019 4:23 pm
Forum: RTL-SDR Discussion
Topic: Long USB-cable vs long antenna-cable?
Replies: 18
Views: 33393

Re: Long USB-cable vs long antenna-cable?

Yet another possibility for connecting to a remote antenna is to plug an RTL-SDR directly into a tiny computer, such as a Raspberry Pi 3 or Zero W, and put that near the antenna. Then run rtl_tcp on the Pi, and use either a long ethernet cable or WiFi from the Pi to connect to your router or desktop...
by hotpaw2
Thu Dec 27, 2018 5:00 pm
Forum: RTL-SDR Discussion
Topic: HF/VHF spyverter and RTL
Replies: 4
Views: 2325

Re: HF/VHF spyverter and RTL

The easiest (and close to the cheapest, since well-constructed antenna switches seem to be expensive) is to simply use 2 RTL-SDR dongles, one for each antenna. The only problem might be that the spacing of the USB ports on your computer is too close for side-by-side RTL-SDR dongles, so you'd also ne...
by hotpaw2
Sun Dec 16, 2018 7:30 pm
Forum: RTL-SDR Discussion
Topic: RTL-SDR V3 long wire problems (SOLVED)
Replies: 12
Views: 6181

Re: RTL-SDR V3 long wire problems

Try putting a 1 MegaOhm resistor between the long wire antenna and a good Earth ground.
by hotpaw2
Sun Dec 02, 2018 8:21 pm
Forum: Troubleshooting Help
Topic: Accessing sdr_rtl output stream programatically in a buffer
Replies: 1
Views: 1348

Re: Accessing sdr_rtl output stream programatically in a buffer

The stream generated by an RTL-SDR (which can be accessed by librtlsdr) is baseband IQ data, not audio. So your best bet is the latter: a pipe from rfl_fm.
by hotpaw2
Mon Sep 10, 2018 4:55 pm
Forum: RTL-SDR Discussion
Topic: SDR - Bandwidth
Replies: 4
Views: 4744

Re: SDR - Bandwidth

Even an analog AM radio has a non-zero bandwidth, usually around 10 kHz wide. An SDR is designed and built with much wider filter bandwidths than your typical analog AM/SW radio. An SDR also uses much higher sample rates (240 ksps to 3.1 msps in the case of a typical RTL-SDR) compared to typical aud...
by hotpaw2
Sat Aug 11, 2018 5:26 pm
Forum: RTL-SDR Discussion
Topic: RTL-SDR dongle over Ethernet
Replies: 11
Views: 8963

Re: RTL-SDR dongle over Ethernet

I use a Raspberry Pi 3 to send USB data from an RTL_SDR via rtl_tcp over the network to my iPhone. If your rtl_tcp server (Raspberry Pi 3, Zero W, et.al.) can't be wired to your ethernet router, and is some distance from your WiFi access point, you could try WiFi with two directional WiFi antenna's ...
by hotpaw2
Tue Aug 07, 2018 4:36 pm
Forum: Antennas
Topic: HF Loop antenna with differential amplifier
Replies: 1
Views: 6810

Re: HF Loop antenna with differential amplifier

Small HF loop antennas are by nature narrow-band. If you remove the tuning capacitor, then that will just let whatever stray capacitances tune the antenna to some random frequency, but the antenna will still have a narrow-band selectivity, not be un-tuned or wide-band. For a wide-band HF antenna, yo...
by hotpaw2
Tue Jun 26, 2018 4:59 pm
Forum: Troubleshooting Help
Topic: problem with iSDR app on iphone X
Replies: 0
Views: 1407

Re: problem with iSDR app on iphone X

The iSDR app does not appear to have been updated for iOS 11.
by hotpaw2
Fri Jun 01, 2018 3:21 pm
Forum: Troubleshooting Help
Topic: Spectrum Display Noise Floor Randomly Lowers
Replies: 6
Views: 3102

Re: Spectrum Display Noise Floor Randomly Lowers

Computer fans, power supplies, voltage regulators, plus USB, network, and video cables (especially cheap ones) can radiate a ton of broadband RF noise into a nearby antenna or unshielded SDR. Motors and LED lightbulbs in the room can be another problematic RF noise source. Nearby radio stations, as ...