The warning paper that comes with the Pro Stick says “This receiver has a high-performance amp that requires a 1090MHz filter or custom gain settings to work correctly.”
Just for clarity, should one expect any sort of problems when using a Pro Stick with a FlightAware 1090MHz filter even if the adjustable gain in dump1090-mutability is set to “max” or “agc”? Specifically, would the stick be damaged in some way by high-power signals (ADS-B or otherwise) that exceed the full-scale reading on the stick?
I ask because I live in an area that is ~150m from a GSM900 tower, and that frequency is at least partially within the FA filter’s passband.
Additionally, the feeder location is in a location that has a reasonably long maximum range (I routinely pick up aircraft 130-150nm away) and so would benefit from amplifying weak, distant signals. It also lies directly beneath a common route for airliners and so gets quite strong ADS-B signals (peak signal strength is around -0.5dBFS, with anywhere between 2% and 20% being >-3dBFS depending on air traffic); I don’t want to damage the stick or otherwise cause problems by over-amplifying these strong, nearby signals.
That signal will not cause any physical damage to your stick. However it may be so loud that you simply cannot hear (or hear very well) the signals you are interested in. Give it a try.
Worth getting a filter and trying. I have read elsewhere recently that that as GSM900 is quite close to 1090MHz and may not be attenuated as much as hoped for on some filters…
Thanks! Just making sure. It looks like I get more messages and flights seen with higher tuner gain, but I didn’t want to risk damage. I get some signals near the full-scale limit, but I’m not seeing saturation where there’s no signal.
As for the filter and GSM, I have a filter and you’re right: GSM900 isn’t as strongly attenuated as one might like. (I mentioned that in my original post. ) Doesn’t seem to be a problem so far, though.
if gsm next to you is around 920-960mhz the fa filter will help almost nothing. i had similar conditions at my site and using the habamp sawfilter amp combined with the standard nooelec dongle helped much …
Yeah, it’s the standard everywhere-outside-of-North-America GSM900, so the FA filter isn’t super great at attenuating it. That said, it hasn’t caused any problems with the standard Nooelec dongle I was using. It also hasn’t caused problems with the filter+Pro Stick setup either, even with the tuner gain at “agc” (though the number of messages with signal strengths >-3dBFS goes quite high and the noise floor moves up, everything continues to work).
The HABAmp looks promising, but alas it’s not really weatherproof and not suitable for masthead deployment. I’d love to put a little preamp up on the mast where signal is less noisy.
yes - was the same at my site. i did not have ‘real problems’ with 920-960mhz - but when i added the habamp i got about 80% more messages and the reason was not only that the signal was amplified but also that the dongle had much less noise to handle that came from the gsm signal. https://store.uputronics.com/index.php?route=product/product&path=59&product_id=50
anthony from habsupplies is a very friendly person - maybe he sells you an saw-filter-amp without housing with a little discount. then you could use one of these cases here: https://www.wlan-shop24.de/Gehaeuse
as the habamp needs only very little juice it is supereasy to power over long usb or antenna cable …
I’m just planning on using a weatherproof junction box with a couple F connectors passed thru the bottom, so I’ll be interested to hear what they come back with.
They said that the existing amplifier/filter is not weatherproof, but they foresee no problems with enclosing it in a suitably weatherproof box and putting it outside.
Additionally, at some point they intend to release a pre-made weatherproof version for sale, but there’s no additional information as to when this would be available. They recommend that interested people follow their twitter feed @uputronics.
) Doesn’t seem to be a problem so far, though.