Noise from speaker

[rogellis]

But as for the Nano 3 and heat dissipation, what happens with the standard dongle is that the chip (the R820T IIRC) gets hotter. The standard dongle does get hot and does heat up the Pi to some extent, but not by that much generally, as the heat transfer through the PCB isn't that great. What the Nano 3 does is dissipate the heat away from the R820T chip, but that means everything else gets hotter.

You are talking about the Stratux low power SDR, which might be a good idea but it appears to be out of stock.
https://www.rtl-sdr.com/product/stratux-rtl-sdr-low-power-rtl-sdr-limited-stock-only

But this is not the Sodial SDR that normally comes with the PAW, which has the same power consumption as the NooElec.
https://www.amazon.co.uk/USB-DVB-T-Stick-RTL2832U-Receiver-Black/dp/B01LYGU4Z2/ref=sr_1_4?ie=UTF8&qid=1516194326

Not sure what you mean by:  'What the Nano 3 does is dissipate the heat away from the R820T chip, but that means everything else gets hotter'.

The heat only has two pathways out of the SDR dongle - either through the dongle casing or through the USB connector.  Since the Sodial has a plastic casing, which cannot dissipate the heat, the heat goes through the USB and into the R-Pi.  If you take the Sodial SDR out of the PAW unit and touch the USB, you can burn your fingers.

Rog.

[rogellis]

Going back to the noise problem, this is an audio of the speaker sounds.  In sequence they are.....

Normal PAW sound, with buzz and click
Silence with a battery source for the speaker.
Back to normal PAW sound, with buzz and click
Deletion of buzz, when I take out the SDR dongle.
Deletion of click, when I take out the wifi dongle.

https://instaud.io/1F2N

So the buzz is from the SDR dongle and the click is from the wifi dongle. 

Rog

[exfirepro]

Hi Rog,

Just noticed your most recent post trying to bring the subject back on line, but as I have spent ages testing and typing this, I decided to post it anyway

[Paul]
You are talking about the Stratux low power SDR, which might be a good idea but it appears to be out of stock.
https://www.rtl-sdr.com/product/stratux-rtl-sdr-low-power-rtl-sdr-limited-stock-only

Out of stock at the moment and not available direct from Stratux, though reportedly available through Amazon.com (US site). Be careful though - I ordered a 'pair' from the same seller's (not Stratux) Amazon UK site but got the 'old' version - which draw pretty much the same current as the Sodial ones, not the 'new' Stratux Low Power ones.   

But this is not the Sodial SDR that normally comes with the PAW, which has the same power consumption as the NooElec.
https://www.amazon.co.uk/USB-DVB-T-Stick-RTL2832U-Receiver-Black/dp/B01LYGU4Z2/ref=sr_1_4?ie=UTF8&qid=1516194326

Not sure what you mean by:  'What the Nano 3 does is dissipate the heat away from the R820T chip, but that means everything else gets hotter'.

The heat only has two pathways out of the SDR dongle - either through the dongle casing or through the USB connector.  Since the Sodial has a plastic casing, which cannot dissipate the heat, the heat goes through the USB and into the R-Pi.  If you take the Sodial SDR out of the PAW unit and touch the USB, you can burn your fingers.

Rog.

What Paul is (presumably) referring to is that TCXO dongles (Nano 3 etc) are designed to remove the heat from the 'chips' to the metal casing, which stops the chips getting too hot while also maintaining a constant temperature inside to control the temperature of the crystal oscillator (which is part of the circuit used to set the frequency). The metal casing should then allow excess heat to dissipate gradually from the casing, but the danger is that much of this excess heat can simply be transferred to the metal USB 'manifold'. In the case of the Nano 3, NooElec have obviously decided to supply an external heatsink because the dongle is so much smaller than 'normal' TCXO dongles such as their own NESDRSmart or RTL-SDR.com's RTL-SDR V3 and so won't be as efficient as dissipating excess heat directly from the casing.

The amount of heat generated with the standard PAW SDR dongles does vary quite a lot from dongle to dongle (these aren't high quality dongles), though I have never had any problems with any of mine. A few users, however, have had issues with SDR dongles failing (presumably due to heat damage), and in a few cases we have also had WiFi dongles melting and think that excess heat from the SDR may be a contributory factor in these cases.

If that is so then the NooElec is probably better, as it is dissipating the energy away from the R-Pi.   I do not have my NooElecs yet, so I cannot test this.  The NooElec engineer said that their dongle consumes 280 ma of power on average, or about 1.5 w.  Which is not very much, so I am surprised this results in such a high temperature.

Yes, by 'host device' the engineer did mean the R-Pi.  I did ask if there were any tweaks that could be made to reduce dongle energy consumption, but it appears not.  Even if less data is extracted from the dongle (like excluding weaker signals from contacts further away), it seems like the dongle will keep on doing its own thing. 
 
Rog

I ran a couple of fairly long term tests yesterday with my Nano 3, and have repeated them again this morning. With the dongle connected to the RPi through a USB Power Meter, yesterday's tests showed an initial current draw of 390mA, rising to a peak of 580mA, then settling to between 390 and 400mA. This morning's test started off at 220mA, which rose to 440mA when the PAW's 'Bridge' came on line (not sure why). The current then 'settled' at between 360 and 430mA which is significantly higher than the figure quoted by your NooElec engineer. This would equate to nearer 2 Watts, which is a fair amount of heat in a small dongle.

I'm not criticising, by the way as I really like the idea of small TCXO dongles, but the advantages have to balance out without creating additional problems elsewhere. I will continue testing.... 

Regards

Peter

[exfirepro]

Going back to the noise problem, this is an audio of the speaker sounds.  In sequence they are.....

Normal PAW sound, with buzz and click
Silence with a battery source for the speaker.
Back to normal PAW sound, with buzz and click
Deletion of buzz, when I take out the SDR dongle.
Deletion of click, when I take out the wifi dongle.

https://instaud.io/1F2N

So the buzz is from the SDR dongle and the click is from the wifi dongle. 

Rog

Hi again Rog, very interesting audio post. You can clearly hear the interference and the effects of removing the SDR and WiFi dongles. I have to say that I am never aware of this level of interference in my plane, but then again I am flying in an open cockpit, so the same noises could well be present, just not audible.

I've just re-read the entire thread. A while back I suggested trying a 'Ground Loop Isolator' between the PAW and your audio interface. Did you ever get round to trying this? It's not really the optimal solution, but I and others have had considerable success using this method to reduce audio interference where the source was difficult to eliminate otherwise.

These are the sort of things I would try, I have used both to good effect previously....

https://www.amazon.co.uk/gp/product/B01IETQQQK/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

https://www.amazon.co.uk/gp/product/B01LYYRT7M/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

Worth a try....

Regards

Peter

 

[rogellis]

I have to say that I am never aware of this level of interference in my plane, but then again I am flying in an open cockpit, so the same noises could well be present, just not audible.

A while back I suggested trying a 'Ground Loop Isolator' between the PAW and your audio interface. Did you ever get round to trying this?

You would not notice any noise in a light aircraft, as your headset will have a difference electrical source to the PAW.  I only have this problem because the PAW and the speaker run from the same dc converter (the speaker is attached to the PAW unit).   

I did not know what a GL isolator was, but I see it is advertised to cure the very problem I appear to have.  And it is not very big, so I think I will get one.

Cheers,
Rog



 

[rogellis]

The metal casing should then allow excess heat to dissipate gradually from the casing, but the danger is that much of this excess heat can simply be transferred to the metal USB 'manifold'. R may be a contributory factor in these cases.

Still not sure about this argument.

The Nano will take the generated heat to the metal casing. This will dissipate much of the heat directly to the atmosphere, via radiation and gas conduction.  So perhaps 60% is dissipated through the casing, and only 40% goes through the USB.

With the Sodial, the heat cannot be transferred to the insulating plastic casing.  Since heat cannot be destroyed, it only has one option, which is to make the i ternal chips much hotter, and to eventually travel down the USB.  So perhaps 90% of the heat will go through the USB in this case. 

So the Nano has to be the better option (if these dongles are drawing the same current).  BTW, the different current draw will be because of the number of contacts it is tracking.  The more contacts, the greater the processing power required to decipher it all.

Thanks for the current-draw figures.  I might go back and ask the engineer where he got his figures from.   All I know is that I ran the complete PAW unit for 10 hours from from 12v, 5 a/hr battery.  Admittedly there was not too much traffic to track, but that probably only works out at 4w average draw.

Cheers,
Rog

[rogellis]

A while back I suggested trying a 'Ground Loop Isolator' between the PAW and your audio interface. Did you ever get round to trying this?

Th GL isolator was delivered this morning (why...?) via Amazon, and the problem is solved.  This gadget really is a PFM box, because it was the noisiest chanell ever, as you heard, and suddenly it is quiet.  All I need to do now, is find room in the box for yet another component.

I will still check out the Nano-3, when it finally arrives...

Thanks,
R

[exfirepro]

Hi Rog,

Thanks for the update and glad the Ground Loop Isolator has sorted your audio problem.

The Nano 3 actually seems to work fine, and with the heat sink fitted - although it still runs hot - 'HOT' is even printed on the casing - it's not so hot you can't touch it. It's just with my (fire service) background I get a bit paranoid about putting hot things inside a plane. (Engine is OK in my case  - it's outside !)

Best Regards

Peter

[rogellis]

The Nano 3 actually seems to work fine, and with the heat sink fitted - although it still runs hot - 'HOT' is even printed on the casing - it's not so hot you can't touch it.

Peter,

The Nano-3 arrived today.  And it makes the same feedback buzz noise as the Sodial dongle, so no change there.

Regards the heat, it is much as I expected.   If you run the Nano for an hour, the casing is very hot just as you say.  But if you pull it out, the metal of the USB is almost cold.    ...    Conversely, the Sodial casing is only warm after an hour, but if you pull it out the USB is burning hot.

So it does appear that the Nano-3 is much better for the Ras-Pi motherboard, because it is dissipating the heat to the environment, rather than through the USB to the Ra-Pi. 

So I think I am now ready for my second build.   
DC converter,
Inline fuse,
Ground Loop Isolator,
Amplifier,
Speaker,
Nano-3 with radiator,
GPS on top of the Ra-Pi,
Wires galore.....

Its going to be a jam-packed box.....

Cheers,
Rog

[exfirepro]

Rog / Sean,

Thought you would like to know I have just arranged to return my Nano 3 to Amazon.

It crossed my mind yesterday, that during my recent tests, when I was concentrating on measuring the current drawn by the dongle, I hadn't noticed any traffic 'on screen'. At the time I subconsciously put it down to the heavy snow falling (Glasgow Airport was closed during part of the test period) and/or perhaps just one of Edinburgh's 'less-busy' periods, so thought nothing more about it at the time.

Thinking about it again later, I began to wonder, so checked my screen grabs from my initial Nano 3 tests on 8th January, which showed the Nano 3 'Connected' and recognised by PAW, with 1090 Traffic visible on the PAW Traffic Page and on Sky Demon, so it was working fine then. Unfortunately I hadn't bothered taking screen grabs while running the load tests, so I re-ran a test yesterday morning and the result was - Nano 3 Connected but no ADSB Messages and a Red ADSB 'light' throughout the test.

I repeated the test with 2 x different RPis, interchanging the Nano 3 with a standard 'Sodial Type' dongle, but using the same 'standard' antenna for both dongles that I had used for the previous tests. I was careful to only exchange the dongles when there was CAT ADSB traffic visible on screen inbound to Edinburgh (at least 3 aircraft with others following and some visible at altitude from my window). The traffic was visible on screen with the standard dongle, but disappeared when I replaced the standard dongle with the Nano 3 (yes, I waited for the dongle to become re-established each time) and reappeared again as soon as went back to the standard dongle. The results were exactly the same with both RPis, so it seems that the Nano 3 has now 'died', possibly resulting from (or in) the extreme heat and unexpectedly high current draw (compared to that quoted by NooElec) ??

Undeterred, I will order another one (or perhaps two) and continue testing. Hopefully, I just had a 'Friday duffer'.

Regards

Peter

BTW - If no-one has any objections, I'm thinking of asking the Mods to split this thread and move 'Answers 30 - 45. 47, 50 and 54' to a separate thread titled NooElec NESDR Nano 3. It will make both threads much easier to follow by anyone reading them in future.

[rogellis]

Rog / Sean,

BTW - If no-one has any objections, I'm thinking of asking the Mods to split this thread and move 'Answers 30 - 45. 47, 50 and 54' to a separate thread titled NooElec NESDR Nano 3. It will make both threads much easier to follow by anyone reading them in future.

Good idea. 
I will reply separately, in that case.

R

[rogellis]

Peter,

Regards the noise from the speaker, I thought you might like to hear the results.

This recording has two 'PA' calls in the normal configuration, then some shuffling as I fit the Ground Loop, and two 'PA' calls with the Ground Loop fitted.

https://instaud.io/1HIo

R

[rogellis]

Peter,

Regards the hot Nano-3  -  did you manage to measure the current draw for the Chinese dongle?
        (Compared to the 400 mA for the Nano...)
I must admit my Nano does get unbearably hot - although the USB is still stone-cold, which is a bonus.
So at least the Ras-Pi is not overheating...

I will do a long term test again, to judge the total time on a 7ah lead-acid battery (perhaps 5ah available).
The Chinese dongle managed 10 hours, before the system died, indicating a total draw of about 5amp.
     (I don't have an ammeter....)

.

I noticed this blog report, that said the NooElec Nano-2 was very RF noisy (presumably meaning wasteful too), compared to other Nano dongles.  And it ran 40ºf hotter too. 

But this posting did not mention that the cooler dongles may be simply dissipating their extra heat into the Raspberry-Pi.    The similar power consumptions of the two nano dongles would indicate that they are generating similar heat, so the temperature comparison may not be valid.

Again they are giving a 270 mA draw for the Nano-2, rather than your 400 mA draw for the Nano-3.

https://www.reddit.com/r/stratux/comments/614xn9/new_low_power_v2_sdrs_and_comparisons/#bottom-comments

Below is a graph of the RF noise from four different SDR dongles. 
The Stratux low power V2 looks like a good option, if it goes back into production.
It appears to be not available at present.

Rog





.

[rogellis]

This is the Stratux low power V2.
But it is sold naked, and vulnerable. Not so bad if everything is inside an enclosure.

https://www.amazon.co.uk/Stratux-1090ES-UAT-Radio/dp/B01N9NNS2H

R

[Ian Melville]

That link is NOT the Stratux low power V2. Ask me how I know 🤔

The correct version has a black PCB and no IR Detector, I have one.

Here are some tests I did, the top pair is the ones linked above.
The attached image shows the dongles collection I have, the power consumption in Watts and the temperatures in three locations with an IR spot thermometer. The three locations are 1. the chip and USB shield junction, 2. The R820T chip 3. MCX connector. Room temp was 70 degrees F and each SDR was run for 30 minutes before readings taken

The Stratus Low Power V2 has a white insulator in the USB plug and the PCB is reversed compared with the others. PCB is also black or dark blue.

I don't have nor intend to test the ability to hear weak signals at our chosen frequencies.
http://whmc.org.uk/RTL-SDR_Dongles.jpg