Search found 176 matches

by hotpaw2
Sat Oct 10, 2020 1:47 am
Forum: RTL-SDR Discussion
Topic: Direct sampling to bandwidth output, how done?
Replies: 10
Views: 3701

Re: Direct sampling to bandwidth output, how done?

You can found some of my software for SDR receivers, transceivers and vector network analyzers, include firmware and apps here, on rtl-sdr site and on github. Good for you. Note that I also have DSP software on GitHub, as well as multiple DSP and SDR apps in the iOS App Store, and a few (long ago) ...
by hotpaw2
Thu Oct 08, 2020 7:03 pm
Forum: RTL-SDR Discussion
Topic: Direct sampling to bandwidth output, how done?
Replies: 10
Views: 3701

Re: Direct sampling to bandwidth output, how done?

Sorry. That's incorrect. Maybe you didn't read the fine print in your textbooks. Anti-alias filtering in software is quite common. This filtering should be done in software (or FPGA gateware) any time the sample rate is reduced to below the previous sample rate (for spectrum or signals that potentia...
by hotpaw2
Thu Sep 24, 2020 6:04 pm
Forum: RTL-SDR Discussion
Topic: Reception of NooElec R820T SDR mini
Replies: 1
Views: 869

Re: Reception of NooElec R820T SDR mini

Depends on the SDR software you choose. The SDR Mini just samples the RF spectrum, but depends on a software application (there are many to choose from) to decode those generic samples as FSK (or whatever).
by hotpaw2
Fri Sep 11, 2020 3:55 am
Forum: Off-Topic
Topic: short active usb cable
Replies: 4
Views: 7306

Re: short active usb cable

A short high-quality passive USB cable (I use 6 inch ones with a right-angle connector) is likely to work better than an active cable.
by hotpaw2
Thu Sep 10, 2020 9:54 pm
Forum: RTL-SDR Discussion
Topic: Direct sampling to bandwidth output, how done?
Replies: 10
Views: 3701

Re: Direct sampling to bandwidth output, how done?

Anti-alias filtering can be done in hardware only for analog signal (before ADC). This is impossible in software (in digital domain after ADC output). The only way is to apply anti-alias filter to the analog signal before ADC input. If you decimate in software, and the sampled signal has a bandwidt...
by hotpaw2
Tue Sep 01, 2020 6:45 pm
Forum: Troubleshooting Help
Topic: Ceiling Fan AGC?
Replies: 7
Views: 8115

Re: Ceiling Fan AGC?

This type of noise likely has nothing to do with your RTL-SDR or your computer or software. It could be RF generated by the commutator in the fan motor, sparking or just causing fast-rise-time switching square waves, which emit lots of RF harmonics. This RF is then coupled into the room's AC wiring,...
by hotpaw2
Mon Aug 24, 2020 3:01 pm
Forum: RTL-SDR Discussion
Topic: Can any RF chip be modded to turn into an sdr or only R820T?
Replies: 6
Views: 1859

Re: Can any RF chip be modded to turn into an sdr or only R820T?

Depends on what you mean by an SDR. Most WiFi, cellular, and mobile phone radios are SDRs internally. So you don't need to turn them into an SDR, as they already are SDRs. However the RF frequencies and modulations these SDR chips are capable of are often fixed to specifics bands and modes, and the ...
by hotpaw2
Tue Aug 18, 2020 2:39 pm
Forum: Troubleshooting Help
Topic: want to broadcast radio [!help]
Replies: 4
Views: 1553

Re: want to broadcast radio [!help]

Some countries allow license-free broadcasting within a limited range of frequencies if one stays below mandated power levels and transmits with a given spectral purity. An amateur radio license will allow one to use even more frequency bands at much higher power levels. Check the requirements for y...
by hotpaw2
Mon Aug 17, 2020 8:43 pm
Forum: Troubleshooting Help
Topic: Librtlsdr vs SDR# sensitivity
Replies: 1
Views: 841

Re: Librtlsdr vs SDR# sensitivity

Check your rtlsdr_set_tuner_gain, rtlsdr_set_tuner_gain_mode, and rtlsdr_set_agc_mode settings.
If the AGC is off and your RF gain is way down, the RTL-SDR sensitivity will be low.
by hotpaw2
Mon Aug 03, 2020 3:44 pm
Forum: RTL-SDR Discussion
Topic: Direct sampling to bandwidth output, how done?
Replies: 10
Views: 3701

Re: Direct sampling to bandwidth output, how done?

The mathematically correct solution is to use a perfect band-limiting anti-aliasing or low-pass filter before decimation or interpolation. In reality, no filter is perfect. So an anti-aliasing filter should have a stop band attenuation below the radio's desired noise floor at and above the new downs...