FlightAware Discussions

New model of BG7TBL noise source

#21

@SoNic67

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#22

Oh, it is a nose source, interesting :joy:

#23

Well spotted :rofl:

image

#24

The SMPS I think is this one:

The amplifiers I think that they are an alternate marking of SBB5089Z:
https://www.qorvo.com/products/d/da001309

In this case, the SMPS absolutely needs to make exactly 5V, to feed those amplifier IC’s.
The 12V can be applied via limiting resistor directly to D4, does not need stabilization of any kind.

#25

My experience (and other’s as well) is that feeding the device at 12V DC converted this device into a frying pan (unless you add a cooling fan).

At 5V DC it not only stayed nominally hot, but also performed good.

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#26

See my site www.pa0nhc.nl for checking and changing.
73’s, Nico.

#27

Nice cat :slight_smile: & nice PCB Catalog

#28

Hey, there is a difference in what a board should do and what actually is doing.

My latest experience: this SATA adapter that I just received in mail, well wrapped and protected.

The capacitor was just rolling in the box. The board would randomly lock up the computer. Don’t know if is because of that capacitor or is something else not caught by QC.

#29

See : www.pa0nhc.nl
Do not feed with 5.0V. The MMICs then will be under powered. In a good PCB, the MMICs automatically get a correctly 5V if the PCB is powered by 12V. The (12V - 5V =) 7V drop occur over R8, R9 and R10.
I measured a PCB surface temp of abt. 65C. That feels hot. But MMICs will not be damaged.
I installed the 78L09, its output C’s and the changed 100 Ohm series R5 for D3 externally on top, like a hey stack. All components must be connected as short as possible near the D3. It is not looking nice, but it works. The 78L09 ensures good separation from power supply noises, as all extra 100uF capacitors do too.

I drawed a PCB according to these mods…
Nico.

3 Likes
#30

Characterizing the SWR of an Antenna with a Noise Source and an RTL-SDR

http://youtu.be/SAAF2FvV9g4

Low cost zener-diode noise generator for use with above spectrum analyzer
Source: http://hansvi.be/wordpress/?p=91

Above circuit is based on the circuit below
Source: http://holdenc.altervista.org/avalanche/

Another Noise Generator.
Source: http://www.n5ese.com/noise.htm

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#31

The LED above is installed backwards, it will just illuminate nicely, that will never work as noise genrator. You need a Zenner diode in reverse connection.

#32

To buck convention, the cct is drawn with the positive rail at the bottom and the ground at the top.
Perhaps the author has a fetish for positive-earth cars (last sold in the '60’s AFAIK)

#33

I was talking about this circuit:

The ground is negative and LED is in direct conduction. Not a very good source of noise.
On the other hand the 2N2222 are not wide band either, max 225MHz (at beta 1) so… yeah, that’s a noise for FM radio band (if lucky).

#34

Ooops - sorry. I mistook the alignment ‘+’ for the polarity.

Terms like “wide band” mean different things to different people. In this case the author is interested in HF (< 30MHz), so the design (even if it worked properly) - as you say, would be useless at 1090MHz.

Looking at the BG7TBL Nose Source (mine it yet to produce it’s first nose), I just had a poke with a multimeter (Fluke 17b+).
Mine is the: 2016-03-06 with the BB5Z MIMIC’s (SBB-5089)

I set the input to: 12.00V (233mA)
Voltage drop across D2: 0.63V
I then measured the supply each MIMIC (w/ 50Ω load) at junctions of:
U2: R8/L6 - 4.73V
U3: R9/L7 - 4.82V
U4: R10/L8 - 4.66V
The Spec sheet gives Vmax as 5.5V.
I had to wind up the PSU to 16.5V to get 5.5V on the first MIMIC (U3)

Several people report these ‘noise sources’ run hot, but based on the measurements above, I’d guess one of the following:

  • The MIMICs are non-genuine (ie. not as per the data sheet)
  • The 12V PSU/Wall Wart etc. is putting out a lot more the 12V - Time for a new one.

Edit: I’ve had mine powered up for half an hour. While it’s getting warm, the 100Ω dropping resistors (R8, R9, R10) are hotter than the amplifiers.

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