Author Topic: "NOSE SOURCE BG7TBL 2016-03-06"  (Read 4626 times)

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Offline rhb

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"NOSE SOURCE BG7TBL 2016-03-06"
« on: October 09, 2017, 11:54:07 pm »
Submitted for your amusement.  Just off the boat from China.

A scope trace of the output from the SMA into a DS1102E through a 6 dB attenuator with 9 V input.

I'll post the input to the zener after supper.

 

Offline rhb

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #1 on: October 10, 2017, 12:53:20 am »
Here's the voltage  applied to the zener diode.

For the benefit of those who are new to electronics, at every setting of the horizontal sweep, the output trace  attached to the previous post should look the same.  That would be the case if DC were applied to the zener.  But if you apply a modulated voltage to the zener you get modulated noise which does not have a flat spectrum.

Sadly, almost any attempt at designing a diode noise source would be better.  I'm amazed that these things are still being sold.

The 3 MMIC amplifiers are Qorzo SSB5089Z parts  which expect Vcc of 5 V.  There is no 5 V regulator that I can see.  The Qorzo parts are specified for 50 MHz to 4 GHz.  So woe unto anyone wanting to check HF filters  with one of these.

If anyone knows of a schematic please let me know.  I *think* it could probably be hacked into something sensible.  Meanwhile I'm going to take up the matter with Paypal.
 

Offline DaJMasta

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #2 on: October 10, 2017, 06:51:56 am »
I assume this a broadband RF noise source?  So the important part is how it looks on an SA, right?  I also wouldn't expect a DS1102E to have anywhere near the bandwidth to get any good information on its performance if it extends up to 4GHz...
 

Offline technogeeky

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #3 on: October 10, 2017, 11:23:06 am »
I assume this a broadband RF noise source?  So the important part is how it looks on an SA, right?  I also wouldn't expect a DS1102E to have anywhere near the bandwidth to get any good information on its performance if it extends up to 4GHz...


Yes. Unless the noise source has been redesigned:

1) It requires a 12V, not 9V.
2) An oscilloscope (especially not a 100 MHz one) is not the intended target.
3) The intended target is a spectrum analyzer which can normalize/calibrate out the noise source, then passing the same signal through a DUT (or through coupler or bridge).

In other words, the quality of the noise source at any particular frequency or bandwidth isn't the goal. It's supposed to be use in cases where you don't have a tracking generator (or you can't use the tracking generator you have).

 

Offline Cerebus

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #4 on: October 10, 2017, 12:31:40 pm »
I think what several posters are missing is that a noise source is very definitely not supposed to have obvious periodicity and any noise source is pretty lousy if it doesn't either have something close to a Gaussian spectrum or some other well known spectrum such as 'pink' noise.

However, if you turn the oscillograph through 90 degrees, it does look like quite a good repeated nose source.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline technogeeky

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #5 on: October 10, 2017, 12:39:15 pm »
I think what several posters are missing is that a noise source is very definitely not supposed to have obvious periodicity and any noise source is pretty lousy if it doesn't either have something close to a Gaussian spectrum or some other well known spectrum such as 'pink' noise.

However, if you turn the oscillograph through 90 degrees, it does look like quite a good repeated nose source.

Couldn't this be explained by providing insufficient voltage to the device? I haven't taken mine apart or reversed it, but I do remember powering it with different voltages and the spectrum changed pretty wildly at 3 volts underneath.
 

Offline rhb

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #6 on: October 10, 2017, 02:05:15 pm »
I didn't have a connector to feed it 12 V so I used a 9 V wall wart on my bench.  I shall repeat with an adjustable PS once I locate a barrel plug.

However, the pulse input to the zener diode is pretty damning.

As for the DSO vs SA.  I don't have an SA.  But the fact remains that a true white noise signal is fractal in the time domain.  At every sweep setting the scope trace should look the same, a constant amplitude noise.

I suspect that switching from linear X scale to log X scale will show that the low frequency end of the spectrum is really bad at any voltage.  But please, if you have one of these and an SA, post some traces.
 

Offline wraper

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #7 on: October 10, 2017, 02:19:16 pm »
I suspect that switching from linear X scale to log X scale will show that the low frequency end of the spectrum is really bad at any voltage.  But please, if you have one of these and an SA, post some traces.
http://www.amateurtele.com/index.php?artikel=218
 

Offline wraper

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #8 on: October 10, 2017, 02:22:05 pm »
At every sweep setting the scope trace should look the same, a constant amplitude noise.
Have you heard about aliasing on DSO?
 

Offline tggzzz

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #9 on: October 10, 2017, 02:22:32 pm »
I didn't have a connector to feed it 12 V so I used a 9 V wall wart on my bench.

So, let me get this right, you are criticising the component despite knowing that you are providing an incorrect and invalid PSU?
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Offline TurboTom

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #10 on: October 10, 2017, 03:07:50 pm »
The flyback converter that´s included on the PCB to generate the ~36V to bias the 24V "nose" zener (IIRC) is crap. I tried everything (different inductors, capacitors, feedback networks...) to keep the output voltage from oscillating without success. To me it seems the STM flyback controller (MC34063A) just isn´t able to provide a sufficiently clean output voltage at the low current load (loop oscilation). Otherwise, the noise performance of the little gadget doesn´t seem too bad.

Cheers,
Tom
 

Online Mechatrommer

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #11 on: October 10, 2017, 03:51:28 pm »
"NOSE SOURCE BG7TBL 2016-03-06"
...get modulated noise which does not have a flat spectrum.
However, if you turn the oscillograph through 90 degrees, it does look like quite a good repeated nose source.
yeah the noise is inconsistent thats why you see the "I" keep missing...
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline cdev

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #12 on: October 10, 2017, 04:40:44 pm »
What we should also be concerned about is the almost certain ripping off by somebody of BG7TBL's callsign as a sort of trademark in order to market this thing.

If anybody here has interacted with the real BG7TBL, could they maybe shoot him an email notifying him of this situation so he can take it up with whomever might be able to help him if such an entity exists (it very well may not in China but I suspect web sites like ebay and taobao would likely see the point, that this was abuse of what amounts to a sort of trademark or name and stop this.)

Were it not for the misspelling this trick would likely have been more successful.

Next time they will likely consult a dictionary before posting their ad.
« Last Edit: October 10, 2017, 04:42:42 pm by cdev »
"What the large print giveth, the small print taketh away."
 

Offline technogeeky

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #13 on: October 10, 2017, 04:50:21 pm »
What we should also be concerned about is the almost certain ripping off by somebody of BG7TBL's callsign as a sort of trademark in order to market this thing.

If anybody here has interacted with the real BG7TBL, could they maybe shoot him an email notifying him of this situation so he can take it up with whomever might be able to help him if such an entity exists (it very well may not in China but I suspect web sites like ebay and taobao would likely see the point, that this was abuse of what amounts to a sort of trademark or name and stop this.)

Were it not for the misspelling this trick would likely have been more successful.

Next time they will likely consult a dictionary before posting their ad.

bg7tbl is a Chinese seller. His or her primary storefront is on taobao, I think.
 

Offline rhb

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #14 on: October 10, 2017, 04:56:21 pm »
I did a lot of searching for BG7TBL and found nothing.  I think it is probably a fake call sign.  I looked in vain for a schematic to avoid having to create one from the board.

A call sign query at:

https://www.qrz.com/db

produced  a "no data" response.  BG is a Chinese prefix.
 

Offline DaJMasta

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #15 on: October 10, 2017, 05:10:41 pm »
While there's certainly a chance, I suspect it's too elaborate of a fake to be true.  This is the primary taobao store https://bg7tbl.world.taobao.com/

There is an email listed, I have read documentation (though only the block diagram and specs in English) for other BG7TBL devices, and the scope of the products offered is pretty much limited to RF and timing related electronics designs - exactly what you'd expect from a ham who's making designs to make some inexpensive tools available.

I don't have the noise source and am unable to test for myself as a result, but it really seems to me like you're jumping down the throat of whatever designer made it without even trying it under normal conditions or in the intended manner.  Undervoltage measurements on equipment that has a bandwidth of a tiny fraction of that it should be outputting means aliasing city if not unintended low voltage consequences (like periodicity from the RC time constants as the power parts charge).

Would be interesting if anyone had actually contacted the person, as the equipment has shown up here a few times, but I get the impression that their English may be limited from the documentation/storefront/etc.
 

Offline technogeeky

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #16 on: October 10, 2017, 05:28:43 pm »
While there's certainly a chance, I suspect it's too elaborate of a fake to be true.  This is the primary taobao store https://bg7tbl.world.taobao.com/

There is an email listed, I have read documentation (though only the block diagram and specs in English) for other BG7TBL devices, and the scope of the products offered is pretty much limited to RF and timing related electronics designs - exactly what you'd expect from a ham who's making designs to make some inexpensive tools available.

I don't have the noise source and am unable to test for myself as a result, but it really seems to me like you're jumping down the throat of whatever designer made it without even trying it under normal conditions or in the intended manner.  Undervoltage measurements on equipment that has a bandwidth of a tiny fraction of that it should be outputting means aliasing city if not unintended low voltage consequences (like periodicity from the RC time constants as the power parts charge).

Would be interesting if anyone had actually contacted the person, as the equipment has shown up here a few times, but I get the impression that their English may be limited from the documentation/storefront/etc.

I already own the noise source. I will capture some example time and frequency domain measurements and report back later today.
 

Offline cdev

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #17 on: October 10, 2017, 09:04:16 pm »
We should ask Blueskull what he thinks - he would also be in a position to send him a heads up in Chinese or via qq or whatever..

EDIT: looks like his email is : bg7tbl@126.com

(Alternatively, one doesnt need to know English or Chinese to send him photos of the device, the oscilloscope output, the PCB with his name on it. Just like any of us looking at a schematic likely can understand some basics of what its doing without speaking another language.  Ive often witnessed scientists who speak virtually no common language communicating via the blackboard, expressing whatever concepts they want to communicate often doesnt require grammar.. Usually they use math.. its the same thing. )

Suppose it is his, completely getting away from the functionality or lack of it, we've all made our share of spelling and grammatical errors, even if it is genuine, he would deserve to know how ridiculous "nose source" sounds to us.

But I suspect that BG7TBL is likely a real ham, and more likely than not he's an RF engineer, or close to one in terms of his skill, who is being ripped off

He likely is well enough informed and speaks good enough English that he likely wouldn't make such a bad spelling mistake, (but not so good that he feels comfortable attempting to communicate in it)

and that instead, somebody is stealing his call sign to distinguish a inferior product from others.

If thats the case we should make an effort to let him know this is being done.

My mother used to say "let there be peace on earth and let it begin with me"

« Last Edit: October 11, 2017, 01:13:27 am by cdev »
"What the large print giveth, the small print taketh away."
 

Offline technogeeky

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #18 on: October 10, 2017, 11:45:06 pm »
I took some measurements with my oscilloscope (Rigol 1054z).

edit: I didn't check until I was done with all measurements, but my unit indeed says NOSE SOURCE. Heh.

The test setup is as such:
  • power supply
  • bg7tbl noise source
  • SMA dc block (18 ghz)
  • SMA 10dB pad (18 ghz)
  • sma cable
  • sma to bnc
  • bnc 50 ohm through terminator
  • Rigol 1054z


TIME DOMAIN

First, your measurement: 20us/div, measure rms, vpp, avg. 9V input

Note: Your settings were 10V/div, trigger at 10V, unknown termination.
Note: My settings are 200mV/div, trigger at 540mV, 50 ohm termination.




Second, same measurement but 12V input:




And finally, this one I'm happy about:

Same measurement but input voltage swept from 12.0V to 8.88V (CH2).





FREQUENCY DOMAIN

For the next two, low frequency (first few MHz) FFT:

Measurement Settings:
  • 100 ms/div
  • FFT (Memory*)
  • 500kHz/div
  • 10.0dBV/div
  • 2.50MHz center
  • -60dbV

Noise Source OFF


Noise Source ON




For the next two, same thing but over the full bandwidth of the Rigol 1054z (approx. 130 MHz)

Measurement Settings:
  • 100 ms/div
  • FFT (Memory*)
  • 25.0MHz/div
  • 10.0dBV/div
  • 65.0MHz center
  • -60dbV

Noise Source OFF

Note the spurs and the noise floor level assuming no spurs:



Noise Source ON (note: This is accidentally 200 us/div, but it doesn't matter)

Note the relative flatness across the range (horizontal marker 2 is about 130 MHz, the 3db point).

I think the jumping is either due to triggering or FFT window edge effects, or both, or neither. I really don't have a clue. Hence AC triggering to randomize. :-//



Here is the 200us/div version, but with the 20M bandwidth limiter on (as a sanity check):



I will follow up later tonight with actual spectrum analyzer measurements.

I'm not a noise, RF, or any other relevant kind of expert so I'll let others draw conclusions from these pictures, if any can be reached. I think the difference between 12V and 9V is quite significant, though.
« Last Edit: October 10, 2017, 11:54:14 pm by technogeeky »
 

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #19 on: October 11, 2017, 12:10:07 am »
there are plenty of sub harmonics there, or aliasing? not sure, but why the op hasnt thought of utilizing all of them into good use? he'll be sorry arse to know his dreamed monotonic is of no use on other than the nose freq, for the purpose he intended to do (filter respond) .. and, i suspect it will not be long that the op will joint ebay treasure hunt club. Or worst, too long than expected because he join applied mathematics club beforehand...
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline cdev

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #20 on: October 11, 2017, 01:21:01 am »
Is this device the same one both of you two gentlemen have?

The jpeg compression artifacts on my screen make it impossible to tell from this whether it says "noise" or "nose".

 it says he has sold 6 of them. So you have two?
« Last Edit: October 11, 2017, 04:59:55 am by cdev »
"What the large print giveth, the small print taketh away."
 

Offline Dwaine

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #21 on: October 11, 2017, 01:28:43 am »
I love the screenshots.  How did you get the animation? 
 

Offline technogeeky

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #22 on: October 11, 2017, 04:49:43 am »
Here are some measurements with a spectrum analyzer. For instrument limitation reasons, I split the overall measurement into two bands:

  • 500.0 kHz to 375.0 MHz
  • 375 MHz to 2.7 GHz
  • (addendum: 500.0 kHz to 1.00 MHz)

In all measurements that follow, the equipment setup is connect as follows:

  • noise source
  • 10dB pad (DC to 18 GHz)
  • SMA to Type N adapter
  • Agilent E7495a

And I show both Peak detector (which is "normal" for a spectrum analyzer) and Sample detector (which is perhaps more appropriate when measuring no signal at all - e.g. noise)

To start, the insertion loss characteristics of the noise source (this includes the insertion loss of a good quality 18 GHz type N to SMA adapter):





DC to 375 MHz





375 MHz to 2.7 GHz





2.0 GHz to 2.2 GHz (spectrogram)[1]






500 kHz to 1.0 MHz

Finally, we can take a detailed look at the behavior of this noise source where it has far too much harmonic structure to be considered noise of any kind. As far as I can tell, this really only takes place in the first 1 MHz or so (this effect was visible a little in the Rigol, including in screenshots I didn't take). In this frequency range, the noise source is very (I mean very very) sensitive to the input voltage. Changes of 0.1 to 0.2 volts can have a dramatic effect. It looks pretty much fine here at 12.0 to 12.1 volts input (not shown - it looks the same as the 11.2 volts picture). But take a look at these:








[1]: I picked this band because I was getting very clear spikes from wifi in the band I wanted to target (2.3 to 2.5 GHz).

 

Offline technogeeky

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #23 on: October 11, 2017, 04:57:17 am »
My conclusion, if I may be so bold, is that this is actually a pretty damn good broadband noise source. Especially for $20. Granted, I don't have any professional counterparts to compare (they cost in the many hundreds to many thousands). But if you exclude the periodicity in the DC to 1 MHz range (which can be avoided by careful choice of input voltage), then overall this is certainly a sufficient source of noise to use as an input for things like amplifier bandwidth testing, antenna sweeping, noise combining, etc. All of the things you might want to do if you do not own a tracking generator. Heck, this can be useful even if you don't have a spectrum analyzer: a cheap $20 SDR can be used along with spectrum sweeping software and a directional coupler or RF bridge would be a pretty powerful way to sweep antenna.

If anyone has any follow up questions or measurements you want me to make, please feel free to ask.
 

Offline technogeeky

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Re: "NOSE SOURCE BG7TBL 2016-03-06"
« Reply #24 on: October 11, 2017, 05:04:18 am »
...
Question on your sweeps.. Sometimes cables - especially badly terminated ones have peaks and notches in them, in terms of response, but I have never seen anything that moves like that. Are you sure thats the device under test causing that? Have you looked at it with some other kind of sensor? Also, have you ever put a known good noise source or sweep oscillator on your same test setup?

I'm not sure what you mean by moves (please quote a specific image), but I don't think I made any mistakes with regard to termination nor did I use any bad cables or connectors. The only cables I used were SMA cables known to be flat to 6 GHz, and interconnects known to be flat to 18 GHz. Of course, the Rigol 1054z is only known to be flat to about 130 MHz.

I don't have any other noise sources. I have a few other choices when it comes to sweeping frequencies, including a 25 MHz function generator, a pair of devices also made by bg7tbl (25 mhz - 6 ghz SMA spectrum analyzer, 135 mhz - 4.4 ghz SMA spectrum analyzer) which can be used to generate RF singals, and highest quality of all, the bidirectional source of the Agilent E7495a which can output -90 to -23 dBm of power from 375 MHz to 2.5 GHz in 0.1 dBm steps.

This leaves some overlap between the Agilent and the Rigol, but when I compare devices where possible (e.g. the 25 MHz function generator into the E7495 spectrum analyzer, or the 25 mhz - 6 ghz into either/both the Rigol and the E7495) everything behaves as expected.
 


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