Do I Need A Filter?


#213

sorry i couldnt get back to you guys yesterday…i exceeded the post for the day. I went back and redownloaded rtlpan.exe and it works fine, i guess the first time i downloaded it, i didnt get all the file. I only got a 39kb file so i had to redown it. I still couldnt get it to work on win 10 and i followed the link evangelyul posted and i didnt see nothing on there either to fix it. I made a scan.csv file in the folder but it didnt help so now i copied the 3 files from the x64 folder and it seems to be working for now


#214

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True. Just a little higher than close highest object, say few feet above it.
Beyond that, not much benefit.


#215

Do I Need (yet another) Filter?

I have been reading this full thread and I really need some advise to get rid of some noise in my set-up, which is located in Europe approximately 5 NM from an international airport:

  • FlightAware 66cm antenna
  • FlightAware Pro Stick Plus
  • FlightAware 1090MHz Band-pass Filter
  • CLF200 cable, 1 meter

Elevation of the antenna is approximately 30 meters and it is in a high density urban area with cell towers near by. Besides that it is next to a large police station with a lot of antennas on the roof for emergency communication.

As you can see below the external filter does a pretty god job at getting rid of noise in the 800 - 850 MHz, 900 MHz, 1060 MHz and 1110 MHz spectrum, but even with this filter there is significant noise in the 930 - 960 MHz spectrum:

With no external filter:

With external filter:

Any suggestions are welcome.
And thanks for a great forum!


#216

Jetvision have an excellent cavity filter (I bought two).

Uputronics also have excellent amp/filters (I have many for 1090Mhz, 978Mhz and 145Mhz)
https://store.uputronics.com/index.php?route=product/product&path=59&product_id=50
They require bias-t or USB power.


#217

The blue dongle has a SAW filter after the low noise amplifier so with some help from the bandpass filter it’s quite similar to some of amps with saw filters.
So right now your filter chain looks like this:
bandpass filter -> LNA -> SAW

Another option is the RTL-SDR BLOG 1090 MHZ ADS-B LNA.

SAW filters have high attenuation so they optimally need a LNA to compensate the loss.
So you will basically only see SAW filters after LNAs. The RTL-SDR amp/filter does this twice, the filter chain is:
high pass filter -> LNA -> SAW -> LNA -> SAW

This is a great thread explaining some filters but it’s quite technical.


#218

Seems to be this one
£16.50, Free postage

https://m.ebay.co.uk/itm/ADS-B-1090MHz-Filter-RTL-SDR/263929220631

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#219

If you can live with the Bias T inconvenience, the RTL-SDR Blog pre-amp and filter combo is a tremendous value. I have one, and would not think twice about buying a second one when the need arises.


#220

You mean this one?


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#221

Yes, this is the one I currently use, specifically for ADS-B.

I also purchased their generic one, just released, for use with my RSP1A wideband SDR.

The generic one will also work for ADS-B, with one of the low cost SAW filters, in a pinch.


#222

Options:
Buy finished product- US $9,99

Solder the product yourself -

Aliexpress: SAW TA0232A 0232A Filter 1090 MHz - US $7.98 / lot 5 pieces / lot , US $1.60 / piece


A filter has one problem - there are no capacitors at the input of the signal and the output of the signal. Ccapacitors protect the SAW from damage by D.C.


#223

This is the $18 preamp with two filters that I got on eBay:


#224

What’s the performance like?

I have one of the same, that I ordered before they added the SAW filters, for $10. Never used it, so no idea if it even works.


#225

That is the most difficult thing to do.


#226

Well… it works, using it right now to feed two devices (spliter). I had to lower gain a lot because both my tuners have amps inside - one FA orange and one blue (I’m at gain 12dB now).
Does it make a difference? A little. But I still want to raise my antenna more…


#227

FA antenna, FA Pro Stick Plus and FA ADSB filter tests
spectrum without ADSB filter…the signals around 860Mhz are the local police and emergency services that run APCO P25 Phase 1 and their antenna is about 3 miles from my house. The signals around 960Mhz are pagers from local hospitals


spectrum with ADSB filter

Waterfall without ADSB filter

Waterfall with ADSB filter

The external ADSB filter definitely cleans up the signal even thou the Pro Stick Plus has a built in filter


#228

Which external filter did you use?


#229

Opps…i meant to mention that…it was the Flightaware ADSB filter from Amazon


#230

It’s doing its job, good!

The PS+ has only one SAW filter, I think.


#231

@venom6733

The FA external filter is very good to chop-off GSM-800 Mhz, but practically ineffective to remove EGSM-950 Mhz

From your scan plots, it looks that either there is no EGSM-950 in your area, or the Pro Plus’s SAW filter removed it successfully.

If you conduct the scan with a GENERIC DVB-T, and without any external filter, the plot will show what RF signals exist in your area.


#232

I may do that later…I have a rtl-sdr, so ill see what happens