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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Tue Mar 14, 2017 7:35 pm 
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inoc - FlightAware user avatar

Joined: Sat Dec 18, 2010 11:00 am
Posts: 23
Thanks for all the info, I was thinking about putting an "ultra" low noise amp (~0.6db at 1090MHz) in front of the prostick+, but with both the prostick+ and prostick having an about 0.23dB NF LNA at 1090MHz I sure don't want to do that.

I guess when I think about noise it's in the pass band of the demodulator, any noise outside the demodulated pass band has no effect on performance (unless it overloads something in front of the demodulator).

And you are of course correct on the term system temperature as being an all inclusive term for system noise, varying with the ambient air and component temperatures.
Since ambient air and component temperatures vary with the weather and component cooling methods I usually consider the 1st amplification stage's NF as setting the noise floor.

On the filter, I have the understanding that it reduces both the signal and noise ~2db inside it's pass band but about 40 db outside.
So if there were no LNA in front of the filter, just say a ~2dBi gain antenna, the gain of the antenna would be completely eliminated by the insertion loss of the filter.
OTOH if an LNA with a 0.23 dB NF and ~18dB gain were put between the antenna and filter the antenna gain would only be reduced to ~1.77 dB and the 18 dB of gain would replace the losses due to components temperatures downstream of the LNA, thus the S/N ratio would remain the same downstream of the LNA in the pass band of interest.


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Fri Mar 17, 2017 5:02 pm 
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david.baker - FlightAware user avatar

Joined: Thu Jan 23, 2014 12:34 pm
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inoc wrote:
And you are of course correct on the term system temperature as being an all inclusive term for system noise, varying with the ambient air and component temperatures.
Since ambient air and component temperatures vary with the weather and component cooling methods I usually consider the 1st amplification stage's NF as setting the noise floor.


Definitely the right way to think about how it works. The beginning parts are much more important than the later stages.
This is also the reason we recommend a good antenna and cabling. The biggest increase in performance are in the beginning because once the signal is messed up it can't be fixed in the later stages.

inoc wrote:
On the filter, I have the understanding that it reduces both the signal and noise ~2db inside it's pass band but about 40 db outside.
So if there were no LNA in front of the filter, just say a ~2dBi gain antenna, the gain of the antenna would be completely eliminated by the insertion loss of the filter.
OTOH if an LNA with a 0.23 dB NF and ~18dB gain were put between the antenna and filter the antenna gain would only be reduced to ~1.77 dB and the 18 dB of gain would replace the losses due to components temperatures downstream of the LNA, thus the S/N ratio would remain the same downstream of the LNA in the pass band of interest.


Gain numbers don't quite work like that. dB are relative measurements so you have to know what you are comparing it too. Also dB is logarithmic scale so every 3dB change is about half or twice the power. Something with +3dB higher means it has twice the power. Something -3dB lower means it has half the power. Something with +6dB means it has 4x the power. Something with +9dB means it has 8x the power.

The dBi (it ends with the letter i) is a relative measure compared to a isotropic antenna. A 2dBi antenna means that the antenna has 2dB more gain than an isotropic antenna in the main direction. The other way to think of it is that the antenna instead of antenna receiving energy in all direction it will instead get 2dB more in some directions and a few dB less in other directions.

A dBm (it ends with the letter m) is the power relative to a milliWatt of power. So on an absolute measurement the prostick can measure power levels down to about -90dBm. This is why receivers are usually speced in the lowest power level it can detect in dBm.

You should think of it more like this: A plane has a 200W transmitter which sends the signal through the air and it is picked up by the antenna. The antenna turns the signal into a voltage which is in the microV range. This microV signal then has to be transmitted through the cables , amplified and filtered and you can estimate the final signal based on the gain of each part. So your microV signal has a -3dB loss from the cable, then a 18dB gain from the amp, then a -2dB loss from the filter, and finally a +50dB gain internal to the receiver chip (controlled with the gain setting in piaware). With the right oscilloscope you can measure the voltage at the different stages.

We output the final gain on the local web interface as a dBFS measurement (dB Full Scale). This is a dB measurement based on the receiver scale and it isn't calibrated so you don't know the actual dBm measurement without an oscilloscope. You can see this measurement by clicking on a plane on your PiAware map and then going to the section on the right and read off the dBFS measurement.

Also, there are *lots* of other losses than what we have listed. The main thing is that you get a good signal and then not mess it up in any of the stages.


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Mon Mar 20, 2017 9:35 am 
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WhiteCitadel - FlightAware user avatar

Joined: Tue Nov 17, 2015 10:36 am
Posts: 14
Any update on when any of the Amazon's in Europe will have stock again?


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Mon Mar 20, 2017 9:47 am 
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obj - FlightAware user avatar

Joined: Tue Sep 30, 2014 7:14 pm
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WhiteCitadel wrote:
Any update on when any of the Amazon's in Europe will have stock again?

See post203742.html#p203742. We're not restocking Amazon in Europe because of import issues.


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Mon Mar 20, 2017 9:56 am 
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Joined: Sun Jan 01, 2006 5:00 pm
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Availability on Amazon Europe is provided by ModMyPi going forward (and/or any other future retail partners that choose to sell there). You may prefer to order directly from the MyModPi.com web site. They are temporarily out of stock on the Plus but they have more on the way. Demand has exceeded their expectations (good problem to have!) and they are ramping up inventory.


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Mon Mar 20, 2017 10:26 am 
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WhiteCitadel - FlightAware user avatar

Joined: Tue Nov 17, 2015 10:36 am
Posts: 14
Ah ok - shame about the 50% price hike :(

Amazon was really convenient, even if you could re-stock just one European Amazon it would be good.


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Fri Apr 07, 2017 1:44 pm 
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MarcelK - FlightAware user avatar

Joined: Wed Mar 16, 2016 4:48 pm
Posts: 4
Just noticed they are now available through http://www.rtl-sdr.com/. Cost $24.95 USD, including free shipping worldwide.


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Thu Apr 13, 2017 7:28 am 
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conligwx - FlightAware user avatar

Joined: Sat Mar 18, 2017 8:00 pm
Posts: 87
Location: EGAC/EGAD
Just a quick question, if I were to upgrade from a ProStick to a Prostick Plus would this require any additional setup or would it use the same PiAware setup and report to the same Feeder id on FA?


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Thu Apr 13, 2017 9:17 am 
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If you're only using 1 dongle then it is simple to swap out (plug and play) with no configuration changes. Your feeder site ID will not change.


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Fri Apr 21, 2017 2:34 pm 
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SEFL - FlightAware user avatar

Joined: Mon Apr 17, 2017 4:38 pm
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If I am not mistaken it is said that some will benefit from the additional FA filter even with this built in filter of the Pro Plus. Is that correct? How do I know if I would benefit from the additional filter?


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Fri Apr 21, 2017 2:48 pm 
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In practice the built-in filter will tend to help extend the range (weak signals) but does not protect from overloading the front-end (it's not designed to do that). Many users still benefit from the external filter because it reduces the overall RF noise input to the radio, which is a big issue for users in urban areas or otherwise near powerful radio transmitters. Unfortunately, without knowing the RF noise floor at every installation location, we can't predict conclusively what configuration will work for you. If you're the very rare person with access to a spectrum analyzer, you can do some investigation on your own in advance to try to predict what you need or don't.


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Fri Apr 21, 2017 5:30 pm 
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abcd567 - FlightAware user avatar

Joined: Sat Feb 15, 2014 3:08 am
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SEFL wrote:
.... How do I know if I would benefit from the additional filter?

ericcarlson wrote:
...... If you're the very rare person with access to a spectrum analyzer, you can do some investigation on your own in advance to try to predict what you need or don't.

I also faced this problem. I dont have spectrum analyzer, so I used another primitive, but time proven method: trial & error :D, and it solved my problem.


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Fri Apr 21, 2017 6:17 pm 
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SEFL - FlightAware user avatar

Joined: Mon Apr 17, 2017 4:38 pm
Posts: 21
abcd567 wrote:
SEFL wrote:
.... How do I know if I would benefit from the additional filter?

ericcarlson wrote:
...... If you're the very rare person with access to a spectrum analyzer, you can do some investigation on your own in advance to try to predict what you need or don't.

I also faced this problem. I dont have spectrum analyzer, so I used another primitive, but time proven method: trial & error :D, and it solved my problem.



I ordered it from Amazon and it will be here Sunday. Let's do this!


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Fri Apr 21, 2017 6:30 pm 
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jimcander - FlightAware user avatar

Joined: Mon Jan 23, 2006 5:00 pm
Posts: 1152
Location: KALB
Stood up my Pro Stick on my old pi running 2.1. Tripled my stats...

Wow...


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Sat Apr 22, 2017 10:59 am 
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SEFL - FlightAware user avatar

Joined: Mon Apr 17, 2017 4:38 pm
Posts: 21
jimcander wrote:
Stood up my Pro Stick on my old pi running 2.1. Tripled my stats...

Wow...



Can you elaborate on what you mean by "stood up"? Sorry..newb here.


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Sat Apr 22, 2017 3:13 pm 
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jimcander - FlightAware user avatar

Joined: Mon Jan 23, 2006 5:00 pm
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Location: KALB
Replaced the three year old norco dongle w the pro stick and filter. Made no other changes and still running 2.1 on my three year old pi.


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Sun Apr 23, 2017 8:03 am 
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conligwx - FlightAware user avatar

Joined: Sat Mar 18, 2017 8:00 pm
Posts: 87
Location: EGAC/EGAD
Received my ProStick+ on friday, and fitted it on Saturday. so far a mixed result as Satuday/Sunday are quiet days. I ahve noticed today that MLAT reports are lower than "Other" so far, which is not usually the case.

Setup is as follows: ProStick+FA Filter+FA 26" Antenna. I am going to leave this for a few more days to check from last weeks stats, before trying something else.

Is there any definitive way of knowing you are overloading the receiver? Any linux commands?


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Sun Apr 23, 2017 8:56 am 
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jimcander - FlightAware user avatar

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login in and run type "uptime" It'll give you a rough idea on load. Since I put in the ProStick, I went from .5 or so to close to 1 on my old pi A. I want to put up the new B I have with the new software but I am waiting for the point where I can migrate a MAC based site to a site id based site.

uptime gives a one line display of the following information. The cur‐
rent time, how long the system has been running, how many users are
currently logged on, and the system load averages for the past 1, 5,
and 15 minutes.

This is the same information contained in the header line displayed by
w(1).

System load averages is the average number of processes that are either
in a runnable or uninterruptable state. A process in a runnable state
is either using the CPU or waiting to use the CPU. A process in unin‐
terruptable state is waiting for some I/O access, eg waiting for disk.
The averages are taken over the three time intervals. Load averages
are not normalized for the number of CPUs in a system, so a load aver‐
age of 1 means a single CPU system is loaded all the time while on a 4
CPU system it means it was idle 75% of the time.


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Sun Apr 23, 2017 9:38 am 
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conligwx - FlightAware user avatar

Joined: Sat Mar 18, 2017 8:00 pm
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Location: EGAC/EGAD
ok thanks for that.

Code:
pi@piaware:~$ uptime
14:36:08 up 14:30,  1 user,  load average: 0.31, 0.37, 0.40


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Sun Apr 23, 2017 9:47 am 
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jimcander - FlightAware user avatar

Joined: Mon Jan 23, 2006 5:00 pm
Posts: 1152
Location: KALB
You're good...


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Sun Apr 23, 2017 12:20 pm 
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AlpineMeadows - FlightAware user avatar

Joined: Tue Mar 21, 2017 12:07 am
Posts: 25
jimcander wrote:
login in and run type "uptime" It'll give you a rough idea on load.

Is there a way to do this remotely from the Pi? I have my pi remote mounted and powered over POE. It's not easily accessible.


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Sun Apr 23, 2017 6:06 pm 
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Skibox - FlightAware user avatar

Joined: Tue Nov 17, 2015 12:33 pm
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conligwx wrote:
Is there any definitive way of knowing you are overloading the receiver?


jimcander wrote:
login in and run type "uptime" It'll give you a rough idea on load.


That is a completely different kind of "load".

Overloading the RF frontend with strong interfering signals, as discussed in this thread, often leads to much fewer packets being decoded, giving a very low cpu load.

So, this number tells absolutely nothing about the need for external filtering.

/M


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Sun Apr 23, 2017 6:19 pm 
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jimcander - FlightAware user avatar

Joined: Mon Jan 23, 2006 5:00 pm
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Location: KALB
My interpretation was "CPU" based off the ask for a Linux command. Have at the radio fun. Tweaking that is far from my wheelhouse.


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Sun Apr 23, 2017 6:32 pm 
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Skibox - FlightAware user avatar

Joined: Tue Nov 17, 2015 12:33 pm
Posts: 84
jimcander wrote:
My interpretation was "CPU" based off the ask for a Linux command. Have at the radio fun. Tweaking that is far from my wheelhouse.


This whole thread is about RF filtering (added to the PS+), noise floors, and RF front-end overload.

/M


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 Post subject: Re: Announcing the Pro Stick Plus!
PostPosted: Sun Apr 23, 2017 6:39 pm 
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jimcander - FlightAware user avatar

Joined: Mon Jan 23, 2006 5:00 pm
Posts: 1152
Location: KALB
Really? I thought it was about "Announcing the Pro Stick Plus"


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