Search found 94 matches

by hotpaw2
Tue Jun 26, 2018 4:59 pm
Forum: Troubleshooting Help
Topic: problem with iSDR app on iphone X
Replies: 0
Views: 1329

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: 2774

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 ...
by hotpaw2
Wed May 30, 2018 4:26 pm
Forum: Off-Topic
Topic: Question about frequency mixer?
Replies: 1
Views: 2900

Re: Question about frequency mixer?

It's trigonometry. If you combine two frequency sinusoids by adding them, it won't mix them, you will end up with just 5 and 20. However, if you multiply two sinusoids, then this modulation will produce two side-bands. This is because of the trigonometric product-sum identity: sin(a) * sin(b) == 0.5...
by hotpaw2
Wed May 30, 2018 4:13 pm
Forum: Troubleshooting Help
Topic: Spectrum Display Noise Floor Randomly Lowers
Replies: 6
Views: 2774

Re: Spectrum Display Noise Floor Randomly Lowers

With or without the antenna plugged in? If the noise floor only cycles when the antenna is plugged in, then it could be from some periodic RF noise source in your room, building, or neighborhood.
by hotpaw2
Thu May 17, 2018 3:01 pm
Forum: RTL-SDR Discussion
Topic: Q branch
Replies: 3
Views: 2023

Re: Q branch

If using rtl_tcp, you can send a 5 byte command sequence to the open tcp/ip port, with 9 in the first byte, and zeros in the following 4 bytes to disable Q-branch direct sampling.
by hotpaw2
Wed May 16, 2018 4:25 pm
Forum: Other SDR Devices
Topic: SDRplay to announce a new product at Hamvention
Replies: 6
Views: 16017

Re: SDRplay to announce a new product at Hamvention

The issue I have with SDRPlay is that I heard from other software developers that their device library either doesn't link or doesn't connect to the device on one or more recent versions of macOS or the latest Raspberry Pi OS release. Have they fixed this so that SDR software developers can write ap...
by hotpaw2
Tue May 01, 2018 4:44 pm
Forum: User Projects
Topic: New SDR app for iOS (iPhone)
Replies: 5
Views: 8226

Re: New SDR app for iOS (iPhone)

Forgot to mention, my rtl_tcp SDR iOS app supports LSB and USB on HF (via Direct Sampling or an upconverter), and it also includes a CW audio filter.
by hotpaw2
Mon Apr 30, 2018 3:40 pm
Forum: User Projects
Topic: New SDR app for iOS (iPhone)
Replies: 5
Views: 8226

Re: New SDR app for iOS (iPhone)

Beta testing was successful, and the HotPaw rtl_tcp SDR app is now available from Apple's iOS App Store.

See: https://itunes.apple.com/us/app/rtl-tcp ... ?ls=1&mt=8
by hotpaw2
Sat Apr 28, 2018 7:45 pm
Forum: Other SDR Devices
Topic: Airspy HF+ on a Raspberry Pi?
Replies: 4
Views: 5381

Re: Airspy HF+ on a Raspberry Pi?

My iOS rtl_tcp SDR app is for now available for purchase from Apple's iOS App store: https://itunes.apple.com/us/app/rtl-tcp-sdr/id1351164646?ls=1&mt=8 It supports the HF+ from a Raspberry Pi to an iOS device (but only if you are willing to compile beta-test-level open source code: https://gist.gith...
by hotpaw2
Sat Apr 14, 2018 3:25 pm
Forum: Other SDR Devices
Topic: Airspy HF+
Replies: 7
Views: 5769

Re: Airspy HF+

An Airspy HF+ has a ton more dynamic range than an RTL-SDR, so doesn't need a much control over HF gain and attenuation to catch weak signals. Although an RF band-pass filter and/or broadcast band-stop filter will help almost any radio receiver. Also, I found that libairspyhf provides all the contro...