RTL-SDR Same signal with or without included antenna

mike31337

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Hello Experts,

Any idea why my RTL-SDRs (v3 and v4) have the same crappy signal with or without the dipole antenna kit connected? I'm attempting to listen to 150.000M.

Sorry if this is a stupid question.

Thank you in advance,
-Mike
 

rabbit108

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Jan 4, 2021
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S.E. VA
Hello Experts,

Any idea why my RTL-SDRs (v3 and v4) have the same crappy signal with or without the dipole antenna kit connected? I'm attempting to listen to 150.000M.

Sorry if this is a stupid question.

Thank you in advance,
-Mike
Hello, Mike. It's not a stupid question, because you obviously have a problem.

This is 150 kHz with my RTL-SDR V3:

150 kHz_1.jpg

This is 150 MHz:

150 MHz_1.jpg

Have you tried receiving FM signals with the V3 and SDR# software?

100 MHz_1.jpg

You might be even able to receive NOAA Weather. In my area it's on 162.55 MHz:
 

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morfis

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Jan 24, 2004
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Any idea why my RTL-SDRs (v3 and v4) have the same crappy signal with or without the dipole antenna kit connected? I'm attempting to listen to 150.000M.
What software are you using to control them?

Note the RF gain setting in the screenshots by rabbit108.
In sdrsharp the default when you first use an RTL-SDR in it is zero for the RF gain so there will be no output (but don't be tempted to whack it up to full as that will cause other problems).
 

JvdK

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Apr 11, 2023
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Zeist, The Netherlands
Do you adjust the two elements (telescope’s) of the dipole for 150.000MHz or do you just attach them and use maximum lenght? You can calculate the optimal length of the dipole by dividing 468.000 (for feet) or 143.000 (for metres) by your frequency in MHz. The result is the total length of the dipole, so divide it by 2 and you have the length for each element.

468.000 : 150.000 = 3.12 feet so each element needs to be 1.56 feet

If you want to adjust the dipole for a complete band you can take the center frequency of the band and calculate the length for the dipole😉

Civil airband: 118.000 to 138.000 center frequency: 127.500
 
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Freemor

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Oct 29, 2023
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New Brunswick, Canada
It would be good if you posted a picture os the "crappy signal" as it could be caused by several things.
If it looks like a single spike as if there was a carrier there without modulation you may need to turn on I/Q correction. (i always run with it on for my RTL v3)
If it looks like a plump jiggling mound it may be interference from Strong local FM stations. I had to get a FM trap module as I have a very strong FM station close by that was creating problems for DX-ing.
If there is no of little signal then it may be your gain setting as mentioned above. Make sure that direct sampling is turned off. and consider the location of your antenna. My house has a metal roof that produces serious radio dead zones in the house.

Make sure your antenna is away from your monitor. Most monitors throw horrible RFI all over the place. And there are other thing that can throw a lot of RFI. I had tr replace one router in my house because all the ethernet cables coming out of it were just screaming with RFI.
 

spongella

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Feb 21, 2014
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W. NJ
Not a stupid question at all. If you are receiving a signal on 150 MHz without an antenna attached it is either a birdie or interference. Try moving the SDR(s) to another location and see if the signal changes in strength.

Out of curiousity, what is on 150 MHz that you want to hear?
 

mike31337

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All, my apologies I should have deleted this post. Thank you for your help. I changed the gain with 'rx.py'.

'lna:60" seems to be the sweet spot for me.
 

sunwave

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Oklahoma
All, my apologies I should have deleted this post. Thank you for your help. I changed the gain with 'rx.py'.

'lna:60" seems to be the sweet spot for me.
Is your house covered in some kind of metal siding? You should be seeing signals with way less gain. Perhaps install a discone antenna outside on a mast?
 
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