Reference signal to tune my SDR Dongle

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networkwiz

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I have the NooElec NESDR Mini 2. I'm just getting started with it and I am using SDR# on a Windows 7 laptop. I know that there is some drift from unit to unit that needs to be compensated for to get exactly on frequency.

I am looking for a nice sharp reference signal that I can as a standard for frequency correction. The NESDR receives from about 25Mhz to 1750Mhz. So I would prefer something in that range if possible.

Also, I see a lot of signals that I assume are some sort of artifact from the laptop. I haven't upgraded my antenna yet and I am wondering if that will help.

Thanks to all,

RK
 

boatbod

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Some people like to use a local NOAA weather broadcast. Personally that doesn't work for me since the nearest one is too far away for the indoor antenna. There are also tools that search for and use cellular phone tower. In my case I used the control channel of our local 700Mhz first responder trunked radio system.
 

br0adband

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NOAA weather broadcasts in the 162 MHz range are great for that purpose as long as you're within roughly 100 miles of a mid-size or major airport, and another one I use is the ATSC digital television pilot signal at 470.310 MHz - if you're in the US unless you live someplace hundreds of miles from a TV station (literally) you should be able to get a decent working signal on that frequency and it's pretty stable.

Realize that the RTL-based sticks do have some drift to them unless you're using one of the newer models that has a TCXO (temperature controlled crystal oscillator) so even though you might get a rock solid tuning at 162 MHz it might be off a few ppm at 470.310 and even further off at higher frequencies in the 700-800-900 MHz ranges but in general it's usually easy to get a pretty solid idea of what the best ppm for a given stick is once it's warmed up to operating temps.

And yes, absolutely get yourself a better antenna ASAP if you want to get serious about this aspect of monitoring by using this type of hardware. The tiny crappy antennas that come with most every RTL-based stick are only useful for the basics of testing the hardware to make sure it works and not for serious monitoring. You may need to get a pigtail adapter to convert it from the connector on the stick to something else like a BNC or SMA connector as required so keep that in mind as well. You can build antennas pretty easily with some basic components or put out the cash to get something commercial in nature, it's entirely up to you in that respect.
 

slicerwizard

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I am looking for a nice sharp reference signal that I can as a standard for frequency correction.
Use the highest frequency signal you can find - something in the 700, 800 or 900 MHz bands. After all, you are dealing with PPM, so size does matter. If you had bothered to tell us where you are, we could have given more specific advice.
 

crayon

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Realize that the RTL-based sticks do have some drift to them unless you're using one of the newer models that has a TCXO (temperature controlled crystal oscillator) so ...
I didn't double-check if the mini2 is TCXO but I bought two NESDR Smart's and they are. A TCXO usb SDR is the only way to go.

I got so tired of the air conditioning in my truck drifting the XO.

:D
 

SCPD

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I sometimes use the 310 khz pilot signal on TV stations. Some VHF some UHF. Since I have a 0.5 TCXO equipped dongle I don't set it at all.
 
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nd5y

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Before you use DTV ATSC pilot frequencies as a reference standard you should verify what the actual frequency is.
Some TV stations are offset and the pilot is not always exactly 310 kHz above the lower band edge.
 

ot0tot

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Kalibrate-rtl is a pretty great tool for this. I've successfully used it to calibrate a number of RTL sticks. Run the calibration once the stick is warmed up and you should get a pretty accurate ppm offset.

Github page and linux version:
https://github.com/steve-m/kalibrate-rtl

Windows version:
http://rtlsdr.org/files/kalibrate-win-release.zip

Blog posts on use:
Kalibrate-RTL: Calibrate #SDR (SDR Sharp) Linux/Windows TUTORIAL. | RTL-SDR.Sceners.ORG
https://cognito.me.uk/computers/kalibrate-rtl-windows-build-32-bit/
How to Calibrate RTL-SDR using Kalibrate-RTL on Linux - rtl-sdr.com
 
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