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  #41  
Old 08-23-2015, 11:26 AM
okei okei is offline
 
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Quote:
Originally Posted by humptybump View Post
Given the different PIREPs, I did some reading about various SDR-RTL dongles.

For APRS I've used the old E4000 chipset SDRs. These have proven to be somewhat superior on the 100-450Mhz range. However, they are getting scarse and are typically $40 when compared to the RTL2832U R820T based units which center around $15.

Recently, a few sellers have been offering an updated design for the low cost units. These newer dongles use an R820T2 chip and a few better tolerance supporting components.

The result is the newer units show improvement in sensitizing and reduced noise above 800Mhz.

I hope to test one of the newer units and will update my PIREP above.

E4000 and R820T will not work for this, you'll get spotty results.
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  #42  
Old 08-23-2015, 12:27 PM
humptybump humptybump is offline
 
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Hi "okie". I'm not sure who/where you are or your background. You're profile is blank. You only appear to be associated with this thread.

Quote:
Originally Posted by okei View Post
E4000 and R820T will not work for this, you'll get spotty results.
The R820T will work. I was explaining that independent testers have data showing the R820T2 is a better option.

I hope I was clear to others in saying the E4000 has its uses in the lower frequencies (such as APRS), the R820T units are prolific (so many may have one lying around), and this project seems to benefit from the newer R820T2 devices.

I was trying to give some data to those who might be experimenting and to help with choosing the better component hardware.


The reddit user has given links to Amazon for the RPi bundle and others pieces (and may be making money from every purchase). Some of us may already have pieces and are experimenting with what we have. As I identify differences I'm trying to share to help others. We are here to learn and share.


BTW: for anyone trying to use one of the RT5370 based wifi dongles (common with the canbit bundles and used by many vendors) I have built the latest stable code for hostapd with the necessary support. I'm happy to post them somewhere if you're not comfortable doing raspberry Pi builds.

Last edited by humptybump : 08-23-2015 at 12:36 PM.
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  #43  
Old 08-23-2015, 01:07 PM
gblanck gblanck is offline
 
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Default R820T

Quote:
Originally Posted by humptybump View Post

The R820T will work. I was explaining that independent testers have data showing the R820T2 is a better option.

... the R820T units are prolific (so many may have one lying around), and this project seems to benefit from the newer R820T2 devices.
I had an R820T on hand and put together a Stratux receiver with it- seems to work just fine with reception comparable to my GDL39

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  #44  
Old 08-23-2015, 01:12 PM
humptybump humptybump is offline
 
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Quote:
Originally Posted by gblanck View Post
I had an R820T on hand and put together a Stratux receiver with it- seems to work just fine with reception comparable to my GDL39
Thanks for the PIREP Greg. I'm glad you got good results!

I also tried an SDR-RTL based on the R820T. My results were not as good as my permanent mounted GDL-39. This may be attributed to the superior installation and antenna of my GDL-39 or something else.

I like this experiment so I'll try the different dongle and share what I learn.
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  #45  
Old 08-23-2015, 02:00 PM
okei okei is offline
 
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Quote:
Originally Posted by humptybump View Post
I was trying to give some data to those who might be experimenting and to help with choosing the better component hardware.

Well, at least with 1090MHz ADS-B, it has been tested ad nauseum and R820T2 always comes out the winner. If you were using either an E4000 or R820T RTL-SDR, that is likely the cause of bad "reception" as the qualities of these are inferior for this application.


Quote:
Originally Posted by humptybump View Post
The reddit user has given links to Amazon for the RPi bundle and others pieces (and may be making money from every purchase).

If you're against him making money off of the links, just type in the name of the product on Amazon. They're not custom made for Stratux
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  #46  
Old 08-23-2015, 02:32 PM
humptybump humptybump is offline
 
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Quote:
Originally Posted by okei View Post
Well, at least with 1090MHz ADS-B, it has been tested ad nauseum and R820T2 always comes out the winner.
"ad nauseum" is an exaggeration. The R820T2 has better test results. All of the Internet searches I conducted eventually link back to the same two tests.

Most pilots testing Stratux in this thread are focused on the weather data which is on 978Mhz.

At least one poster has had good results with the R820T. I had marginal results.

If someone has a RPi2 and the older R820T, they can get the Stratux to work. If they are buying everything new, it's beneficial to get the R820T2.
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  #47  
Old 08-24-2015, 07:03 AM
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catmandu catmandu is offline
 
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I am buying everything new (except for the Kmashi, which I have), especially after reading from the Reddit OP, "Yeah, a unit that has a good GPS, pressure sensor, and the AHRS sensors is coming for development. It'll add another ~$50 to the parts list." REALLY glad I did not buy something retail recently, as I intended to do.
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  #48  
Old 08-24-2015, 08:52 AM
rv7charlie rv7charlie is offline
 
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Default Why not....

implement the required pi software routines as an app for android and/or ios?

Sorry for my flagrant display of ignorance; the last real programming I did was back in the mid '70s (previous century).

But if the SDR uses a USB port to communicate, why couldn't the routines running on the pi be run inside android, and avoid the extra hardware? Is it just too much overhead for one device to handle ADSB tasks in addition to mapping?

Charlie
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  #49  
Old 08-24-2015, 09:33 AM
humptybump humptybump is offline
 
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Hi Charlie.

No worries on "the learning curve".

We can dismiss building it with iOS since there is no direct way to get to the necessary internal protocols and no access to the SDR via USB. That leaves Android. ForeFlight does not run on Android.

Last edited by humptybump : 08-24-2015 at 11:21 AM. Reason: Removed incorrect assumption that SDR would use more power than mobile device would tollerate
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  #50  
Old 08-24-2015, 10:06 AM
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dynonsupport dynonsupport is offline
 
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Quote:
Originally Posted by okei View Post
Do you have, by chance, the TSO sensitivity specs for UAT receivers? I'm curious to quantify the difference between the published specs on an RTL-SDR dongle vs that.
I don't know about other brands, but the Dynon ADS-B receiver is about 15dB better than the TSO requires, and it does this in the presence of a +17dBm 1090 transponder pulse.
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