Help requested with outdoor setup with poor reception

Sure, it probably makes sense to expand the description for expert users. Note that it’s a different filter too. I don’t think we’re implying that we’ve somehow hidden the whole external filter inside the dongle - they are different devices! - but maybe that needs spelling out explicitly.

Call me stupid and naive, but I was actually thinking some LC-circuit-magic was done inside the stick, and could be kept small.

No, it’s a completely different filter (a SAW) on the prostickplus. I don’t think there’s space on the board for much of a LC ladder.

Use a shield,a thinner shield may be more effective than a thicker one, since its ability to attenuate is determined in part by the wavelength of the radiation.

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your location is very demanding. most filters because of their high passband attenuation must be placed behind lna. the flightaware external filter attenuates the 1090 signal and 960mhz cellphone about the same amount (see graphs below) - and because of that behavior is a bad choice in most noisy environments outside the us. uputronics saw-filter-lna + generic dongle has much less problems in noisy environments than amped flightaware dongles.

trial and error is the way to go with high-frequency-things - so - again:

  • try using the uputronics saw-filter-lna with generic dongle
  • if noise then is still too high add the jetvision 3-pole filter in front
  • use a quality cable for antenna-run
  • in addition you can give a metal case for pi and/or dongle a try

i’m curious about your follow-up scans with the alternative dongle setup …

flightaware external filter @ 960 mhz ~ 2.0db attenuation:

flightaware external filter @ 1090 mhz = 1.65db attenuation:

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abcd - that’s not a good idea - this saw filter has too much paasband attenuation to place it in front of lna



@abcd567 yes - this is the proof - you loose about 3db @ 1090mhz which means you have just the half signal-power that you have before the filter. and to do so before lna is no good idea when dealing with faint signals like ads-b. the jetvision filter i use just has 0.5db attenuation @ 1090mhz what is nearly the same signal-strength you have in front of …

@skinkie p.s. now saw your ‘all in a box picture’ this is not really a good idea because hf-parts are very close to each other, the temperature could get a little high, zero hf-shielding and the usb cable you use to connect the flightaware dongle could be another possible point of failure …

this is my setup - the 3-pole filter sits in front of uputronics lna so you can’t see it in the first picture

The FA external filter loss is about 1.5 dB, but still gives improvement.
Also an 18 dB pre-amp chip immediately after filter is good enough to recover the 3 dB loss.

You are comparing loss with jetvision in dB.
What about comparing loss in $ £ € ?

The FA external filter loss is about 1.5 dB, but still gives improvement.

-1.5db is muuuch less than -3db but is still not the best decision - and outside the us a bad one

Also an 18 dB pre-amp chip immediately after filter is good enough to recover the 3 dB loss

sorry but this is really nonsense :slight_smile: you simply can’t recover already lost signals - at least in this part of physics

You are comparing loss with jetvision in dB.
What about comparing loss in $ £ € ?

that’s why i always reccomend uputronics filter/lna first - 15$ is what we are talking about:

  • fa-antenna + blue dongle + fa-filter → 80$
  • fa-antenna + generic dongle + uputronics saw/lna → 95$
  • fa-antenna + generic dongle + jetvision 3-pole/cavity filter + lna4all → 170$

edit: another filter that could be used - but in my testing was not as good as the jetvision is the osmocom/sysmocom cavity filter: 1090 MHz cavity filter for Mode-S / ADS-B | cf1090-kt30

  • fa-antenna + generic dongle + sysmocom cavity filter + lna4all → 130$

uputronics saw/lna … hmmm. Here the saw is before lna, just like I proposed for prostick. Why this is not nonsense? :slight_smile:

P.S. if saw is AFTER lna, then it is same as ProStick Plus :slight_smile:

The LNA is before the SAW filter. This particular model is tuned for use with ADS-B frequencies (1090Mhz).

Do you mean the LNA ITSELF is tuned to 1090 MHz?

nope - it’s a mini circuits wideband lna: SMT Low Noise Amplifier, 50 - 4000 MHz, 50Ω | PSA4-5043+ | Mini-Circuits but maybe it’s less prone to overload than the one fa uses. and i’m not talking about theoretical advantages but practical ono-to-one tests i did. you know how much money i had put in all this ads-b tinkering. what does it tell you that i still use the cheapest 10$ dongle? :smile:

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One of my ADS-B systems is very close to a 2 meter (144 MHz) 50 Watt (max) ham FM transmitter. Most of the time I’m running 10 Watts on 2 meters, occasionally going to 25 or 50.

How close are they? They share the SAME antenna. They share a discone on the roof through a Comet CF-413 duplexer.

The high pass part of the CF-413 is rated 830-1400 MHz with a 0.3dB insertion loss max. Isolation between the high pass and low pass sections is at least 55 dB.

I run the high pass output through a short section of RG316 to a sealed enclosure which has a Flight Aware bandpass filter followed by the blue FlightAware SDR and a Pi 3. DC power input is filtered.

I don’t see any appreciable change in ADS-B performance from that system (site 3116, named Scylla) when I’m transmitting on 2 meters.

That site doesn’t do as well as my other one, which uses a commercial antenna and a shorter, higher performance feedline (site 4847, Wombat), but it’s close. And the 2 meter transmitter doesn’t bother that one at all, with an antenna separation of 3 to 4 meters. That system sits in an exquisite cardboard box on my desk, right under my big HF/2 meter transceiver, and has the same RF chain – FlightAware filter, FLightAware blue SDR, PI3.


bob k6rtm

I dont have any problems with my antennas being close to each other 1 adsb beam,amp,rotator, 3 adsb verticals,1 discone,1 dipole. My cable runs are 20 metres height is 9 metres…

Regard Lino.

What is this link dipole.My ?
Dont ever forget to put a space after full stop, else this will convert it into a link :angry:

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I see you have a WiFi dongle right next to the SDR in one of your Pi’s. When I had the same setup, I found the WiFi transmissions overloaded the SDR and I fixed that with a short 15 cm USB extension cable. Have you not noticed any interference?