SDR Sensitivity

[mmediaman]

Sorry if this is a newbie question.

I bought a Nano3 SDR and trying to understand its ability to receive VHF, or any frequency for that matter.

As an example, I tuned it to my local NOAA VHF frequency and it barely gets the signal. I'm using a telescopic antenna and obviously only get the weak signal when the antenna is extended to the optimal wavelength. However, if I compare with my NOAA radio, the NOAA radio can get a much better signal at any antenna length. Even my UV-5R talkie with a duck antenna pulls in the NOAA signal way better.

What am I missing about this SDR technology? (I'm using SDRTouch on a smartphone for tuning)

Thanks for patience with a newbie.🙏

 

[boatbod]

There's always a tradeoff - in this case the SDR's wide receive capability vs a dedicated receiver's better sensitivity.
I've never found any of my various dongles (Nooelec RTL, Airspy, HydraSDR) to be particularly great for pulling in VHF NOAA, but then again I've yet to find a weather radio that works on 700 Mhz public safety either.

 

[mmediaman]

There's always a tradeoff - in this case the SDR's wide receive capability vs a dedicated receiver's better sensitivity.
I've never found any of my various dongles (Nooelec RTL, Airspy, HydraSDR) to be particularly great for pulling in VHF NOAA, but then again I've yet to find a weather radio that works on 700 Mhz public safety either.

Thank you for your reply. 🙏

 

[Ubbe]

As an example, I tuned it to my local NOAA VHF frequency and it barely gets the signal.

What software are using to control it? You can probably select to use automatic gain settings, AGC, don't use those and instead set a manual gain that match with what antenna you have and how much interfering transmitters you have at that specific location.

A dongle doesn't have the same performance as a scanner, it misses vital filters and overloads instantly on any strong signals and then loose receiver sensitivity. Even top of the line scanners like SDS100/200 that use a similar kind of receiver chip have extra filters that has to be manipulated in different ways to allow the scanner to receive somewhat like a conventional non-SDR scanner.

Most SDR dongles isn't properly calibrated in frequency or can drift in frequency after they have been used for a number of hours.

Use something like SDR# and zoom in on a strong digital frequency that most often are GPS calibrated. Zoom in to a level where the whole signal covers a 1/4 of the spectrum display and then go to the settings in SDR# and change ppm offset until the signal are centered exactly on the frequency it is monitoring. Make a note of that ppm value, even write it directly on the dongle, and use that value with any other program you are using with that dongle.

You will see in that SDR# program how the whole spectrum level will rise and even new signals to pop up when the SDR are overloaded, so keep the manual gain low enough to not have that happen too much.

/Ubbe

 

[xicarusx]

There is a bit of a learning curve with an SDR. One you have to learn the software that controls them two you have to understand gain settings, PPM, and use proper antennas. They are extremely sensitive once you dial it in correctly. The Uniden SDS series uses SDR for a reason.

A telescoping antenna isn't going to let you see/hear very much unless you are close to the source of the transmission. Especially the antennas that come bundled with them, non of them are very high gain and they are very broadband. once you get a decent antenna hooked up you won't have much of an issue receiving what you want as far as NOAA goes.

Software is a huge part of SDR. GQRX on Linux or SDR++ on Windows to find your targets. Then there a numerous things out there to monitor and record. SDRTrunk, Trunk Recorder, RTL_Airband are the major players. I have one specifically for NWS Radio. GitHub - TheGreatCodeholio/noaa_weather_radio

Each software has it own settings, but they are fairly similar. Gain setting, PPM setting, device selection, center frequency settings, modulation etc. You have to familiarize yourself with them and how they work in relation to what you are trying to do and your dongle. Also familiarize yourself with Linux. Debian, Ubuntu etc.. A lot of SDR software runs better on Linux, some of it is specifically Linux only.

Like I said there is a bit of a learning curve, but once you get in to it you will wonder why you didn't do it sooner.

 

[dlwtrunked]

There is a bit of a learning curve with an SDR. One you have to learn the software that controls them two you have to understand gain settings, PPM, and use proper antennas. They are extremely sensitive once you dial it in correctly. The Uniden SDS series uses SDR for a reason.

A telescoping antenna isn't going to let you see/hear very much unless you are close to the source of the transmission. Especially the antennas that come bundled with them, non of them are very high gain and they are very broadband. once you get a decent antenna hooked up you won't have much of an issue receiving what you want as far as NOAA goes.

Software is a huge part of SDR. GQRX on Linux or SDR++ on Windows to find your targets. Then there a numerous things out there to monitor and record. SDRTrunk, Trunk Recorder, RTL_Airband are the major players. I have one specifically for NWS Radio. GitHub - TheGreatCodeholio/noaa_weather_radio

Each software has it own settings, but they are fairly similar. Gain setting, PPM setting, device selection, center frequency settings, modulation etc. You have to familiarize yourself with them and how they work in relation to what you are trying to do and your dongle. Also familiarize yourself with Linux. Debian, Ubuntu etc.. A lot of SDR software runs better on Linux, some of it is specifically Linux only.

Like I said there is a bit of a learning curve, but once you get in to it you will wonder why you didn't do it sooner.

"SDRTrunk, Trunk Recorder, RTL_Airband are the major players." Many of us would strongly disagree with that and never use any of those.

 

[mmediaman]

Thanks very much for all the responses.

As mentioned in the OP, I'm using SDRTouch as the software/app on my Android phone (does that count as a UX OS?).

I had SDR++ but can't get it to work any more (does not recognize the driver/dongle). The antenna is a broadband type "RH795" (70hz-1ghz). Guess I was thinking; being able to quickly adjust it to a wavelength multiple would be good enough for something like this. But as mentioned, I have things to learn.

I will play with the agc and other adjustments mentioned and maybe see if I can somehow get the SDR++ to work. I do have CubicSDR on the Mac, so I can learn adjustments there too I suppose.

Thanks again SDR community for being willing to advise me. 🙏

 

[xicarusx]

Thanks very much for all the responses.

As mentioned in the OP, I'm using SDRTouch as the software/app on my Android phone (does that count as a UX OS?).

I had SDR++ but can't get it to work any more (does not recognize the driver/dongle). The antenna is a broadband type "RH795" (70hz-1ghz). Guess I was thinking; being able to quickly adjust it to a wavelength multiple would be good enough for something like this. But as mentioned, I have things to learn.

I will play with the agc and other adjustments mentioned and maybe see if I can somehow get the SDR++ to work. I do have CubicSDR on the Mac, so I can learn adjustments there too I suppose.

Thanks again SDR community for being willing to advise me. 🙏

Yea for sure Android is a Linux kernel. Its not the same as a PC/Mac install of a desktop OS, but yes its a start!

The RTL Drivers for Windows can we weird and finicky, you may need to reinstall them. I am unsure what people are using for indoor SDR antennas as my setups all use outdoor discone antennas. Its probably something broadband that is what you want, you just want something with a little more gain than a telescopic.

Best of luck to you!! I hope you have great success.

 

[Ubbe]

As mentioned in the OP, I'm using SDRTouch as the software/app on my Android phone (does that count as a UX OS?).

I took a look at the app and it has some issues, like when you adjust the gain or set the PPM you cannot watch the spectrum at the same time to see what your different settings will do to the signal or listen to the audio from the signal and adjust gain to the best audio quality.

I didn't had the correct OTG cables to be able to connect a SDR dongle to my USB-C phones so couldn't tell if the spectrum view allows you to properly see if the received signal are exactly centered when adjusting PPM.

/Ubbe

 

[mmediaman]

Got SDR++ working. Needed to clear its cache & data storage for it to properly reinitialize and recognize attached dongle.

Common VHF/UHF talkie whip works well enough and I would venture to say, better than a simple telescopic antenna.

Thanks for all the replies. 🙏