GPIO Airband Bandpass Filter?

[peeeeeta]

I have the RTL-SDR antenna kit and have been trying to pick up airband frequencies with it but its really scratchy and I can almost never pick up ATC, only aircraft. My dipoles are both about 2 feet long and facing vertically in opposite directions.

I live in an apartment building in NYC so height is not an issue but I was thinking that maybe a bandpass filter could help eliminate interference and help me get a better signal after the FA ADSB filter helped a lot when picking up ADSB. I was looking at this bandpass filter from GPIO and was wondering if any of you guys have any thoughts on it. I dont really know much about it but it seems like it might help. Any ideas would help, thanks.

Peter

 

[alcahuete]

I am not familiar with that specific bandpass filter, but bandpass filters will definitely help at eliminating interference. Is it going to be enough to pick up ATC? Don't know. ATC on the ground (specifically at airports) do not use a whole lot of power. Unless you are fairly close to the airport, your chances of picking them up are not very good.

 

[peeeeeta]

I am not familiar with that specific bandpass filter, but bandpass filters will definitely help at eliminating interference. Is it going to be enough to pick up ATC? Don't know. ATC on the ground (specifically at airports) do not use a whole lot of power. Unless you are fairly close to the airport, your chances of picking them up are not very good.

Thanks, the closest airport to me is about 5 miles away. Do you know any other band pass filters for airband?

 

[iMONITOR]

Consider a FM notch filter if you don't already have one. It will help eliminate interference from strong local FM broadcast stations from dissenting your SDR. Play around with the RF gain on the SDR as well. Sometimes lowering it will bring down the noise floor to some degree yet let the desired signal to get through.

What SDR software are you using?

 

[peeeeeta]

Consider a FM notch filter if you don't already have one. It will help eliminate interference from strong local FM broadcast stations from dissenting your SDR. Play around with the RF gain on the SDR as well. Sometimes lowering it will bring down the noise floor to some degree yet let the desired signal to get through.

What SDR software are you using?

I'm using SDR# and right now I have the RF Gain set to about 12.5 - 19.7 dB. I've been playing around with the gain and still the signal is very weak. I uploaded a picture of what the waterfall looks like along with the radio settings at 14.4 dB of RF gain. I also have AF Noise Reduction enabled. I'll look into a Fm Notch Filter too.

Screenshot

Captured with Lightshot

prnt.sc

 

[Ubbe]

I'm using SDR# and right now I have the RF Gain set to about 12.5 - 19.7 dB.

Maybe its dependent of the version of RTL-SDR but my vers 1 needs a gain of 36dB. You can always try and tick the boxes for RTL AGC and Tuner AGC. The sampling rate doesn't need to be more than 1.024MSPS. Cheap SDR dongle receivers lack any kind of filters so the more filter you can use the better it will be. If you are focused on VHF air you could get a airband pass filter to block all other frequency bands. At least a FM trap filter will help but check its specification that it doesn't attenuate the lowest airband frequencies.

/Ubbe

 

[devicelab]

GPIO makes good products. I have a few of their filters and they all work as designed. They also make a good FM trap filter.

 

[peeeeeta]

Maybe its dependent of the version of RTL-SDR but my vers 1 needs a gain of 36dB. You can always try and tick the boxes for RTL AGC and Tuner AGC. The sampling rate doesn't need to be more than 1.024MSPS. Cheap SDR dongle receivers lack any kind of filters so the more filter you can use the better it will be. If you are focused on VHF air you could get a airband pass filter to block all other frequency bands. At least a FM trap filter will help but check its specification that it doesn't attenuate the lowest airband frequencies.

/Ubbe

Thanks, I think that gain was a little too high for me but I might play around with it again. Haven't touched the sampling rate but I do have the RTl A˝C and Tuner AGC boxes checked. I ordered a FM Notch Filter and might consider the airband bandpass filter too.

 

[Ubbe]

I do have the RTl A˝C and Tuner AGC boxes checked.

Then the manual gain setting should be greyed out and not possible to be set. Just check what you can hear with the auto AGC set but usually with my RTL-SDR dongle it creates too much gain and generates intermod issues. Your picture shows the noise floor at -65dBm and that's exactly what I have at a 36dB gain, so it's probably different gain setting values in different versions of the dongle and your 15dB value seems to equal my 35dB.

If you get a airband bandpass filter that attenuates FM broadcast and 155MHz-160MHz NOAA and pager transmitters you'll probably be able to increase gain much more to improve reception.

/Ubbe

 

[Edelweiss]

By the looks of the SDR# screen it seems you are picking up next to nothing. Something must be very wrong, NYC should have tons of loud signals. Check your dongle or antenna cable. Possibly bad connection. Run the spectrum analyser tool. Anyway a broadcast band stop filter can never do any harm. Have you tried hand scanner for comparison?

 

[TomLine]

What does your signal look like in SDR#. Is it sideband? If there's signal your need to filter out, you'll probably see it. AM broadcast will make your baseline look like a roller coaster. FM broadcast will look like itself. Gain is relative. Mine is anywhere from 10 to 35 and the conditions are different every night.