Do I Need A Filter?


Trying lowering the gain setting when using the amp. It may be too high and overloading the dongle.


@Dxista @jonhawkes2030

well it looks ok to me…or not ?

and gain 38.6, after re-optimization.



Let me see how many posting I have made on this topic, before the FA robot tells me shut up.:joy:

Four…I think I’m ok then.:grin:

The CPU is not working as hard, good. The temperature is lower, good. Both ADSB tracks and SNR seem to be the same, but you have more room for stronger signals now, before the RTL overloads, which is good.


I think you can increase the gain a little more. It should peak around the red like.


thank you both guys. :smile:


Have you got link for new graphs your using im still on the old frames
many thanks


no specific link, graphs come with dump1090-mutability (Joe Prochazka’s scripts).




Try this method to update


Ahh failed im running collectd
1.15dev and 3.5.3


Help me out here - what are you trying to achieve by using a bias-t with nothing to power?



oh, mainly satisfy curiosity, ’ what if ', ’ does it work ', experimenting, in an effort to increase message rate.

in it says :

WARNING: Before using the bias tee please ensure that you understand that you should not use
this option when the dongle is connected directly to a DC short circuited antenna. Although the bias 
tee circuit is dual protected against accidental shorts with a PTC automatically resetting fuse and
overcurrent protection on the LDO, short circuiting the bias tee for an extended period of time
(hours) could damage the LDO or fuse permanently. Only use it while connected to an actual
powered device, like an LNA, active antenna or the SpyVerter.

To make things clearer: DC Short Antenna -> LNA -> Coax -> V3(bias tee on) is absolutely fine.
What's not good and makes no sense anyway is DC Short Antenna -> Coax -> V3(bias tee on).
DC Short Antenna -> Coax -> V3 (bias tee off) is fine.

but one option not mentioned is non-DC Antenna -> Coax -> V3 (bias tee on) - if LNA is removed for some reason…


hmmm … ok, but I can’t see how how it could possibly improve your signal - if it did, you wouldn’t need an amp.
Similarly, I don’t understand why turning the bias-t on had a detrimental effect - perhaps someone with an FA filter and a multimeter could check to see if it presents as a short circuit?


Ok the FA filters arrived on Friday and they did what I expected and what a few already new. Basically the noise around 870 to 890 has practically disappeared. The noise around 942 to 958 is still high.

The good news is that the reduction in the 800’s has allowed me to get a similar range and hits on my Dev box (FA Pro, FA ANT) as my other Prod set up (FA Pro with Spider - gain 44.5).

TBH is expected additional range with the DEV set up but that’s said I am still mucking around with gain - currently set to 38.6… perhaps I need to lower further.


I too have purchased this filter, after running my scan i can say that it does knock out a fair bit of noise on both the 800 and 900 spectrum but not all (not for me anyway). I tested with just this filter and also in line with the FA filter. Having both filters didn’t provide any additional filtering, however i did need to ramp up the gain to receive aircraft out at the same range (from 32.8 up to 49 - more than the 2.5 and 2.5 insertion loss)

Ill try just the saw again at a later stage.


I’m back again best figures to date now the english weather is back to normal
here i got latest collectd pics could you comment if this is looking ok
i get so muddled with 3dBFS etc

Postions reported 1,044,893
Aircraft reported 3,448



What changes did you make to your setup on or about 13th August? Your stats jumped impressively.


After checking with Rf scan I saw a lot of 930 - 960mhz cell spikes so I bought me an ADSB filter
installed it and I got no more interference anywhere and about 6th or 7th aug I took it out to check it was indeed working and did another full scan and this was the start of my improvements
so now not needed I think I was a bit OTT with noise
but all is well again



Seems to be this one
£16.50, Free postage





Your collectd graphs look very good to me but I’ll leave it to the experts to comment further. With those figures you should get into the top 100.

How does your range compare with theoretical plotted by Heywhatsthat? I get close to the max in all compass points apart from the North where I’m ~150nm short.

Can you post your full setup please? Antenna, coax run, Pi version, gain setting etc

Many thanks, Dave