Anyone have any experience with the Nooelec Sawbird 1090/UAT preamp/filter? I have one site working with 12-20% improvement in posreps, and distances, but another that is acting like its swamped. Both sites are otherwise identical and have AGC set as the gain in both 978 and 1090 slices of the config file. I’ve double checked everything from an hands on POV. The poor performer is showing 5 or so aircraft very close to site and really low msg rate, which is maybe 3% of what it was doing an hour earlier before Nooelec device was installed today.
FWIW, the device appears well made and has good info with it.
AGC might not be the best setting when using a preamp and filter. This might lead to your reciever being overloaded and by doing that it might become “deaf” for signals.
This would lead to the behavior you are seeing.
Do you have graphs1090 installed ? If so check the percentage of strong signals. That should be around 5% or so.
If not install it
Depending on the results, set a fixed gain on your reciever to see if this situation improves. You can find multiple posts on these forums on how to set the gain for the different forms of installation.
Tuning your antenna right will probably give you a far better result.
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Dank u vel, Tom. I’ll look to implement to the graphs. I’m already using a commercially produced 11db collinear, untunable. I’ve not yet mounted them outdoors. Currently in windows of “third” floor attic at home. ORD area. Lots of traffic with diurnal variation like AMS. I saw mention of the Sawbird by someone in the SNR thread I just read. I’m hoping they may weigh in with thoughts. Best, Scott
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I’ve installed graphs on both my local sites. One using Nooelec and one without. Without has a sub 5% -3dbFS record with an AGC set gain of 49.6. The one with the Nooelec had 17.5% with an AGC set gain of 16.6, so I edited it down to 7.7 and saved the config file. Not having any other luck trying to restart the Pi to ensure the new 7.7 gain (arbitrarily chosen value) I ended up powering the Pi down for about 5 minutes and repowering it. Now hours later, the graphs are showing a reduction to about 13%, but the Misc graph still shows 16.6 gain. I double checked config and it’s at 7.7, so I’m wondering if I’ve missed something. I assumed PiAware-config got read at boot, and edits while it’s running mean nothing. I’ve not found any clues on how to edit the running pi gain. Any insight from my peers?
Hello Scott,
You are using the SD card image and that is overwriting the config file every time you boot
If you are using a PiAware sdcard image, adaptive gain can be configured by editing /boot/piaware-config.txt or by using the piaware-config command.
sudo nano /boot/piaware-config.txt is the correct location for you.
Login to your Pi using SSH
enter the follwing command
cd\
next command
cd /boot
next command
sudo nano piaware-config.txt
Then set the options as described by abcd567
Adaptive gain in dynamic range mode
The dynamic range adaptive gain mode attempts to set the receiver gain to maintain a given dynamic range - that is, it tries to set the gain so that general noise is at or below a given level. This takes into account different or changing RF environments and different receiver hardware (antenna, preamplifiers, etc) that affects the overall gain of the system, and usually will pick a reasonable gain setting without intervention.
To enable this mode:
Set adaptive-dynamic-range no in piaware-config; or
Set ADAPTIVE_DYNAMIC_RANGE=no in /etc/default/dump1090-fa ; or
Pass the --adaptive-range option on the command line.
The default settings for dynamic range will use a dynamic range target chosen based on SDR type (e.g. 30dB for rtlsdr receivers). This is usually a good default. To override this target:
Set adaptive-dynamic-range-target in piaware-config; or
Set ADAPTIVE_DYNAMIC_RANGE_TARGET in /etc/default/dump1090-fa ; or
Pass the --adaptive-range-target option on the command line.
Adaptive gain in “burst” / loud signal mode
The “burst” adaptive gain mode listens for loud bursts of signal that were not successfully decoded as ADS-B messages, but which have approximately the right timing to be possible messages that were lost due to receiver overloading. When enough overly-loud signals are heard in a short period of time, dump1090 will reduce the receiver gain to try to allow them to be received.
This is a more situational setting. It may allow reception of loud nearby aircraft (e.g. if you are close to an airport). The tradeoff is that when there are nearby aircraft, overall receiver range may be reduced. Whether this is a good tradeoff depends on the aircraft you’re interested in. By default, adaptive gain burst mode is disabled.
To enable burst mode:
Set adaptive-burst no in piaware-config; or
Set ADAPTIVE_BURST=no in /etc/default/dump1090-fa ; or
Pass the --adaptive-burst option on the command line.
This mode is more experimental than the dynamic range mode and tweaking of the advanced burst options may be needed depending on your local installation. In particular, --adaptive-burst-loud-rate and adaptive-burst-quiet-rate may need adjusting. Feedback on what works for you and what doesn’t would be appreciated!
Burst mode and dynamic range mode can be enabled at the same time.
Limiting the gain range
If you know in advance approximately what the gain setting should be, so you want to allow adaptive gain to change the gain only within a certain range, you can set minimum and maximum gain settings in dB. Adaptive gain will only adjust the gain within this range. To set this:
Set adaptive-min-gain and adaptive-max-gain in piaware-config; or
Set ADAPTIVE_MIN_GAIN and ADAPTIVE_MAX_GAIN in /etc/default/dump1090-fa ; or
Pass the --adaptive-min-gain and --adaptive-max-gain options on the command line.
If you know approximately where the gain should be, then a good starting point would be to set the max and min adaptive gain to +/- 10dB around your gain setting.
Save the file and reboot dump-1090-fa
sudo systemctl restart dump1090-fa
Use the following command after the restart to check if the setting is correct
sudo systemctl status dump1090-fa
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Tom, once again, dank u vel.
To clarify just one aspect. If I make PiAware-config changes, and then restart dump-1090fa, will that read the new changes? As opposed to a power down reboot of the whole Pi.
Dank u wel 
Restarting dump1090-fa is sufficient to pickup the config changes.
Every restart it will read the content of the config file and use them in the new started dump1090-fa processes.
No need to power down and to reboot the Pi
Do you know if this restart will cause the graphs1090 data loss wiedehopf mentions in his GitHub instructions for them?
No the restart will not lose you data in graphs1090, only during the restart of the dump process so you will lose max 10 minutes.
The data loss wiedehopf is referring to is occurring when you kill the power to the Pi without shutting down normally first.
From the graphs1090 page
“On reboot / shutdown it’s (the data) written to disk and the data loaded to /run again when the system boots back up. Up to 24h of data is lost when there is a power loss.”
In additiin to installing very useful tool “graphs1090” by @wiedehopf, I will recommend installing another useful tool also for easily adjusting gain manually directly from Skyaware map:
https://github.com/abcd567a/set-gain/blob/master/README.md
The “Set-Gain” add-on does NOT determine or tell anything about which gain is the optimum.
It is simply a manual gain adjustment tool. You don’t need to ssh and in terminal open the file /etc/default/dump1090-fa to edit the gain manually. Just select the gain value from drop-down of the set-gain app embedded in Skyaware map, and click button “Set Gain”, and gain will reset to your chosen value, and dump1090-fa will restart with new value of gain in about 5 seconds.
Click on Screenshot to See Larger Size
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I have this LNA and it is working good for me. Installed on 9/27, so 2 weeks of runtime so far. Dual channel antenna in the attic.
I came across 2 documentation problems to report. One is in the datasheet where they recommended their XTR SDR model in the datasheet. However in another Nooelec doc, they say the XTR model is not recommended for ADS-B.
The second problem were the lower labels on the output connectors, the lower labels are swapped. The upper labels are correct, so I covered the lower labels.
I would also check for these documentation errors leading to reception problems. I reported to Nooelec and they agree and fixed/are fixing.
Fran
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Thanks for this input on the labels…I just got mine and recalled you had figured this out!
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