FlightAware Discussions

Dual Dongle and filters

I have Piaware 5 on a RPI 3 and I am adding the 978 dongle. How is everyone using the filters? The FA filter does both bands, has anyone use one filter and split to the two dongles or should I plan for two filters after the split?

Thanks,
Phil

Adding one Light Blue filter before split is as good as adding 2 Light Blue filters after split. In case of filter before split, you save cost of one filter.

That said, the arrangement “two antennas two filters two dongles (NO SPLITTER)” is far better than the arrangement “one antenna, one filter, one splitter, two dongles” OR “one antenna, one splitter, two filters, two dongles”.

Welcome!

First question: have you determined that you really need a filter on one / both bands?
Second: what dual band antenna are you using? (planning to use?)

If you use a splitter, you loose half your signal, so generally, two poor antennas will outperform one good antenna and a splitter.

Yep, separate ant/filter will always be better. I will have to compare the loss when I set everything up.
I am using a ADSBexchange 5.5dBi 1090/978 24" antenna.
My coverage exploded when I setup with that antenna.
I will look at possibly adding another antenna and second filter in the future.

I highly recommend running dedicated 1090 and 978 MHz antennas. The reception bandwidth of the FlightAware (or other branded) antennas doesn’t overlap. For filters, I’m very impressed by Minicircuits (ZX75BP-1034-S+ and ZX75BP-942-S+ in series for 978 MHz, ZX75BP-1090-S+ for 1090 MHz). Though a filter for 1090 MHz with a blue FA dongle shouldn’t be absolutely necessary.

Is an external filter with a FA blue dongle needed?

Short answer is: In some circumstances, yes.

Example:

  • At @foxhunter’s location, Filter did not bring any improvement as his location has low RF noise environment.

  • At my location if I remove the filter, the reception drops to 10%, as my location has very high RF noise environment.

Please see following scans (with & without interna/external Filters) which I conducted about 6 months ago at my very RF noisy environment. I carried out scan as per following guide.

Spektrum - How-to Speedily Scan RF Noise in band 24MHz ~ 1800MHz

The results of scans are below:

The scan 1 shows RF noise picked by antenna and processed without any filter , The scans 2 & 3 were done with filters, and show how filters remove this noise.

Scan 1 of 3 - FA Antenna + Generic DVB-T (no internal or external filter)

Thumb-Generic DVB-T
CLICK ON IMAGE TO SEE LARGER SIZE

Scan 2 of 3 - FA Antenna + ProStick Plus (Only Internal filter of ProStick Plus. No External filter)

image
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Scan 3 of 3 - FA Antenna + ProStick Plus (with internal filter) + External Filter (FA Light Blue)

imageimage
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