Search found 176 matches

by hotpaw2
Sat Jan 30, 2021 7:37 pm
Forum: Antennas
Topic: Loop on ground question
Replies: 3
Views: 910

Re: Loop on ground question

The answer (not that I know) likely depends on (1) the noise floor in your environment versus the sensitivity of your receiver, (2) the frequencies over which you wish to receive, and (3) whether you care about true omnidirectivity (versus directional lobes and nulls). Too large a loop wire length i...
by hotpaw2
Wed Jan 20, 2021 3:33 pm
Forum: RTL-SDR Discussion
Topic: Record whole bandwith spectrum and review later
Replies: 5
Views: 1296

Re: Record whole bandwith spectrum and review later

The bandwidth of the broadcast FM band is 20 MHz, or 2.4 GB of data per minute, which requires more expensive SDR hardware (Lime PCI, et.al.), and a fast computer storage system. An RTL-SDR can reliably transfer over USB 2 only about 2 MHz of spectrum, or only about 10% of the entire FM broadcast sp...
by hotpaw2
Wed Jan 13, 2021 6:47 pm
Forum: Troubleshooting Help
Topic: Has anyone managed to get a Raspberry Pi 4 working with an RTL SDR?
Replies: 15
Views: 19029

Re: Has anyone managed to get a Raspberry Pi 4 working with an RTL SDR?

Just re-compiled rtl_tcp on a Raspberry Pi 4 running the latest Raspberry Pi OS with no issues. The source code I used was from this GitHub repository: https://github.com/osmocom/rtl-sdr Since I wasn't running as root user pi, in the file /etc/udev/rules.d/rtl-sdr.rules , I had to change MODE="0660"...
by hotpaw2
Thu Jan 07, 2021 10:37 pm
Forum: RTL-SDR Discussion
Topic: HF sensitivity of Blog V3
Replies: 5
Views: 1197

Re: HF sensitivity of Blog V3

I have both, and the HF+ Discovery is a very nice upgrade over the RTL in terms of dynamic range, S/N, sensitivity, and IQ offset. The RTL-SDR is mostly for when I need frequencies outside of the range of the HF+ (6M ham band, or UHF) or a wider max bandwidth.
by hotpaw2
Thu Jan 07, 2021 5:47 pm
Forum: RTL-SDR Discussion
Topic: HF sensitivity of Blog V3
Replies: 5
Views: 1197

Re: HF sensitivity of Blog V3

Since there's no built-in LNA in Direct Sampling mode, a long wire antenna (or other large enough HF antenna) may be required to pick up enough signal. However, I've found the it's very easy for any nearby broadcast stations or other strong signals to overload the RTL-SDR V3 in Direct Sampling mode,...
by hotpaw2
Thu Jan 07, 2021 3:30 am
Forum: RTL-SDR Discussion
Topic: AIRSPY basic question
Replies: 3
Views: 748

Re: AIRSPY basic question

If it's an Airspy HF+ or HF+ Discovery, then you can use hfp_tcp (source code on GitHub) to have the Airspy emulate an RTL-SDR running rtl_tcp. And then use any RTL application that supports HF+ sample rates.
by hotpaw2
Thu Dec 31, 2020 4:50 pm
Forum: Troubleshooting Help
Topic: Overcoming Strong Local AM station
Replies: 1
Views: 636

Re: Overcoming Strong Local AM station

Did you try an AM band-stop or 2 MHz high-pass filter? You could also add an attenuator.
by hotpaw2
Thu Dec 31, 2020 2:48 am
Forum: Other SDR Devices
Topic: FunCubeDongle
Replies: 4
Views: 1093

Re: FunCubeDongle

This file in a GitHub repo:
https://github.com/dl1ksv/gr-fcdproplus ... b/fcdcmd.h
seems to define a USB HID value to control the fcdpp bias tee.

What OS are you using? There seem to be some Raspberry Pi tutorials on using libhid to program HID peripherals.
by hotpaw2
Wed Dec 30, 2020 7:13 pm
Forum: Other SDR Devices
Topic: FunCubeDongle
Replies: 4
Views: 1093

Re: FunCubeDongle

I have a FunCube Dongle Pro+ that I acquired about 7 years ago. According to http://www.funcubedongle.com/?page_id=1225 , FCDP+ units did seem to be still available for purchase earlier this year. The basic API seems to be to use USB HID commands to set the frequency, and then it shows up as a 192k ...
by hotpaw2
Wed Dec 02, 2020 6:22 pm
Forum: RTL-SDR Discussion
Topic: Understanding hetrodyning complex values in gnuradio
Replies: 2
Views: 926

Re: Understanding hetrodyning complex values in gnuradio

Any non-zero strictly real signal is really two signals in the complex frequency domain, a positive spectrum signal, and a complex conjugate negative spectrum signal. They have to be complex conjugate pairs for the imaginary part to cancel out, and result in anything strictly real. If not, you get l...