First time RTL-SDR

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Rodield
Posts: 2
Joined: Mon Apr 24, 2017 8:43 pm

First time RTL-SDR

Post by Rodield » Mon Apr 24, 2017 9:44 pm

Hi!

Not long ago i bought a DVB-T tuner with rtl2832 and r820t2.i install it normally but then my knowledge of SDRs, etc. stops. watched videos on youtube, here on page read tutorials but still can not find what i actually need to do, to be able to listen firedepartment frequency. :oops: :oops: i want to use program sdrsharp which should be more than good for beginners like me. In any tutorial shows how to listen to local radio stations but never see the process of getting to listen, firedepartment, air transport, etc. and how to eliminate noise. :?:

I would be grateful of your assistance and further instructions. :)

sorry for my bad English :oops:

im using this tuner
Image

rtlsdrblog
Site Admin
Posts: 2488
Joined: Mon Nov 19, 2012 11:54 pm

Re: First time RTL-SDR

Post by rtlsdrblog » Tue Apr 25, 2017 9:21 am

There's not much to it. First you need to find out the frequencies of the things you're interested in. Google could help there for your local area. You also need to find out if they are using analog or digital communications. Analog is easy, digital is more difficult.

Once you know the frequencies use SDR# to tune into that frequency. Select the mode (fire dept. would most likely be NFM), and click on active frequencies. Adjust the RF gain for best reception.

If the communication is digital, you'd need to research what type of digital communications are used, and then check to see if the DSD+ decoder or other another decoder supports it.

Rodield
Posts: 2
Joined: Mon Apr 24, 2017 8:43 pm

Re: First time RTL-SDR

Post by Rodield » Wed Apr 26, 2017 8:19 pm

probably was a problem with the antenna :? Today I have connected a second antenna and found a few channels to listen. but neither one of these channels is at a frequency which is written for use. frequencies are correct. maybe I'm doing what a mistake that I forgot to configure something?


the same is happening with the frequency for pagers, today I was able to locate it. but I forgot to save it before I look at other frequencies. :? beep was correct as on video from YouTube. it seems to me that it was located at a frequency 173.233Mhz, but I'm not completely sure. Real frequency is 173.250Mhz. all other frequencis have a similar gap.

Why such a difference? and how to fix it?

vitoal-vx5
Posts: 6
Joined: Sun May 07, 2017 5:46 am

Re: First time RTL-SDR

Post by vitoal-vx5 » Tue May 09, 2017 6:44 am

The tuner is not precise, it maybe a few Hz off.

I suggest using SDR# and buy a cheap FRS radio like this:
https://www.amazon.com/BaoFeng-UV-5R-Du ... ds=baofeng

The list of FRS frequencies is here:
http://www.buytwowayradios.com/blog/200 ... ncies.aspx

NOTE: Depending on your country and location transmitting on these FRS (Family Radio Service) frequencies may or may not be legal.

Find out what frequency RTL-SDR is receiving on and compare it to the actual channel frequency on a walkie talkie.
Most softwares give you a way to program in an offset.

rtlsdrblog
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Posts: 2488
Joined: Mon Nov 19, 2012 11:54 pm

Re: First time RTL-SDR

Post by rtlsdrblog » Tue May 09, 2017 11:47 pm

Rodield wrote:probably was a problem with the antenna :? Today I have connected a second antenna and found a few channels to listen. but neither one of these channels is at a frequency which is written for use. frequencies are correct. maybe I'm doing what a mistake that I forgot to configure something?


the same is happening with the frequency for pagers, today I was able to locate it. but I forgot to save it before I look at other frequencies. :? beep was correct as on video from YouTube. it seems to me that it was located at a frequency 173.233Mhz, but I'm not completely sure. Real frequency is 173.250Mhz. all other frequencis have a similar gap.

Why such a difference? and how to fix it?
Yes these basic cheap units will have a frequency offset, because they do not use a Temperature Compensated Oscillator (TCXO). You can correct for some of the error using the PPM correction in whatever software you are using.

Higher end RTL-SDR's cost a few dollars more and use a TCXO, so they will only have a very small 0-2 PPM offset.

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