FlightAware Discussions

Cheap filter experience?

Hello there!

I am considering the addition of a filter to my setup, as my receiver has strong signal from GSM towers nearby (I’ve ran a scan and extracted the heatmap), and as the FA dark blue filter is nearly impossible to source, I’m looking elsewhere, out of curiosity.
Does somebody have tried this kind of filter?

Or would I just be wasting money on buying such filters?

Regards,
Guillaume.

Flightaware offers it’s own filter which is also only a little more expensive.
It can work, but it depends on several things.

I would start reading the thread “Do I need a filter” with lots of information and tipps how to identify the need of a filter.

Hi,

Thanks for your reply. I’ve already read (I may not be up to date, though) that thread, from which I’ve taken the tools to generate the spectrum map.

And that’s how I’ve been tempted to add a filter, although my antenna is too low to expect a huge range improvement.

What you also should consider is your max range per geography and other obstacles. Did you check heywhatsthat.com for your theoretical max range?

I changed antenna to a Jetvision and i have attached also the blue FA filter. There’s no big difference as i am already at the max. performance.

Even a test with an Airsquitter (Radarcape) did not show a significant performance increase.

But spending 20 bucks for testing should be worth the money

Yeah OP already mentioned he was having trouble sourcing the dark blue FA unit. I have not purchased the filter that’s listed, but am about to so I can take it apart and scope it just out of curiosity sake. From the description, I can only guess that they are using the Tai-Saw TA0970A saw filter. I assume this because I have a few of the Chinese double filtered LNA’s that I think are made by the same outfit and they use the Tai-Saw filters in those.

That said, I’d suggest the RTL-SDR Triple-filter LNA as they tend to work very well for most applications. I wont get into whether or not you need a filter - that’s something you’ll need to ascertain yourself based on testing in your environment. Too many variables to recommend with much authority really.

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That’s the part i missed…

One of the comments on the product page mentioned that the applied filter is a SF9179. It also mentioned the input and output were reversed.
According to the data sheet, the insertion loss is >3.88 dB @ 1090MHz.
That means you would lose a lot of faint signals.

This cavity filter would be a better option.

Just like @Nitr0 mentioned the (Bias Tee Powered) RTL-SDR ADS-B Triple Filtered LNA will even do a better job. Hardly any insertion loss, decent filtering and solid amplification (good linearity).

The Triple filtered LNA is a cheaper and similar performer as the Cavity filter+LNA.

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Great eye! I totally missed that. Sort of a gnarly insertion loss especially if going inline pre-LNA and I’d probably steer clear now knowing that beings there are many other options out there as mentioned. Me loves the cavities, but they are more beer money. Get what you pay for in the end usually.

Hello all,

Thanks for your advices. It seems I could order the dark blue FA filter from the UK. I’ll let you know what I’ll do with that.

Best regards.