AM frequency help with rtl-sdr USB

Main forum to discuss RTL-SDR related topics.
Username
Posts: 599
Joined: Sun Oct 09, 2016 7:27 am

Re: AM frequency help with rtl-sdr USB

Post by Username » Sat Dec 21, 2019 12:29 pm

Are you from Spain? If Yes receive the Airband is illegal!
If you record, tell anyone anything about is highly illegal.
If you receive some Military it can be hight treasury. :lol:

You need atleast 2 thinks:
1) an LNA: I pick one from here: http://stores.ebay.com/gpiolabs/ the are the best on the marked and easy to buy.
2) an perfect Antenna:
a) I got my Discone from here: http://www.ebaystores.co.uk/Sigma-Euro- ... 581&_pgn=2 please Note a Discone Antenna have 0db Gain! The are from the Freq who are not commonly in use ok.
This work perfect for me: https://www.sirioantenne.it/en/products ... -lb-series

Maxnalex
Posts: 2
Joined: Sat Dec 14, 2019 10:00 pm

Re: AM frequency help with rtl-sdr USB

Post by Maxnalex » Sat Dec 21, 2019 9:11 pm

I find Airspy works fine for civil and military airband https://airspy.com/download/

An exteral antenna, even a simple 1/4 wave whip is worthwhile and what you hear depends on your location.

K3RLD
Posts: 31
Joined: Sun Sep 01, 2019 12:43 am

Re: AM frequency help with rtl-sdr USB

Post by K3RLD » Sun Dec 22, 2019 8:01 pm

Can you see the signal in the waterfall? Have you selected AM as the demodulator?

alyousufi
Posts: 10
Joined: Wed Dec 18, 2019 8:54 pm

Re: AM frequency help with rtl-sdr USB

Post by alyousufi » Sun Dec 22, 2019 10:13 pm

Username wrote:
Sat Dec 21, 2019 12:29 pm
Are you from Spain? If Yes receive the Airband is illegal!
If you record, tell anyone anything about is highly illegal.
If you receive some Military it can be hight treasury. :lol:

You need atleast 2 thinks:
1) an LNA: I pick one from here: http://stores.ebay.com/gpiolabs/ the are the best on the marked and easy to buy.
2) an perfect Antenna:
a) I got my Discone from here: http://www.ebaystores.co.uk/Sigma-Euro- ... 581&_pgn=2 please Note a Discone Antenna have 0db Gain! The are from the Freq who are not commonly in use ok.
This work perfect for me: https://www.sirioantenne.it/en/products ... -lb-series
Hello dear thanks for the links
No I am not from Spain😂😂 just i show to you from ES amazon.

alyousufi
Posts: 10
Joined: Wed Dec 18, 2019 8:54 pm

Re: AM frequency help with rtl-sdr USB

Post by alyousufi » Sun Dec 22, 2019 10:16 pm

K3RLD wrote:
Sun Dec 22, 2019 8:01 pm
Can you see the signal in the waterfall? Have you selected AM as the demodulator?
Yes I SELECTED AM but I nothing to receive . Maybe because of the antenna .??

Username
Posts: 599
Joined: Sun Oct 09, 2016 7:27 am

Re: AM frequency help with rtl-sdr USB

Post by Username » Sun Dec 22, 2019 10:18 pm

Well the SDR is not that good and the Antenna is a Joke... :D

alyousufi
Posts: 10
Joined: Wed Dec 18, 2019 8:54 pm

Re: AM frequency help with rtl-sdr USB

Post by alyousufi » Sun Dec 22, 2019 11:19 pm

Username wrote:
Sun Dec 22, 2019 10:18 pm
Well the SDR is not that good and the Antenna is a Joke... :D
I am waiting for another antenna to be delivered then I will inform you if it's work or not.

Username
Posts: 599
Joined: Sun Oct 09, 2016 7:27 am

Re: AM frequency help with rtl-sdr USB

Post by Username » Sun Dec 22, 2019 11:29 pm

Depend o n the Gain it will help.
Do you also buy the LNA who I posted the link to?

aurgathor
Posts: 103
Joined: Wed Apr 25, 2018 8:14 am

Re: AM frequency help with rtl-sdr USB

Post by aurgathor » Mon Dec 23, 2019 8:32 am

I assumed you want to receive something relatively low frequency because it's AM (my bad), but I just searched,and airband appears to be 108 - 137 MHz. Most likely you need a good quality FM bandstop or FM low pass filter and possibly a LNA to receive that band.

As long as the FM broadcast stations have a significantly higher signal level (and chances are that's the case) you're DOA without some filtering or down conversion.

Traditional FM receivers normally downconvert the FM broadcast signal to a 10.7 MHz IF, and work from that, but there are double or triple converter designs for higher quality receivers.

K3RLD
Posts: 31
Joined: Sun Sep 01, 2019 12:43 am

Re: AM frequency help with rtl-sdr USB

Post by K3RLD » Tue Dec 24, 2019 2:39 pm

As long as the FM broadcast stations have a significantly higher signal level (and chances are that's the case) you're DOA without some filtering or down conversion.
I listen to airband all the time with no LNA and no FM bandstop filter. I'm not saying that it can't kill his reception (it definitely could), all I'm saying is your statement is not a definative.

The OP needs to supply a lot more information for us to really help. OP, what is the noise floor of the airband while you are listening. can you see the RF signals on the scope? or do you just see the noise floor? (an attached screen capture would really help).

For example, here is my RTL-SDR.com V3 Dongle connected directly to the cheap telescoping antenna that shipped with the dongle, sitting on a pizza pan about 1 meter from my laptop (no bandstop filter, no LNA). The two continuous lines are birdies or real continuous signals (not sure, didn't investigate them) - but all the little short lines are airband transmissions that are loud and clear. Noise floor here is about 65db.
Image

As a comparison, here is the FM broadcast band:
Image

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