Search found 20 matches

by Brightnoise
Fri Sep 21, 2018 2:19 pm
Forum: User Projects
Topic: The LM339N trouble in my project
Replies: 1
Views: 14349

Re: The LM339N trouble in my project

Nobody does answer. I will do. Your conclusions are right and there is no further error in your circuit. LDR in the dark rises LDR resistance; input on negative rail is then a low voltage and the inverted output is high: no LED indication. Changing plus and minus inputs results in "LED is ON when LD...
by Brightnoise
Sat Sep 01, 2018 9:29 pm
Forum: User Projects
Topic: How to assure the lf353n opamp?
Replies: 1
Views: 14196

Re: How to assure the lf353n opamp?

So you want an interface that converts a digital signal to a digital signal.....
And you want to use an opamp....
Why?
A simple 2-transistor circuit can do this.
Or do I miss something?
by Brightnoise
Mon Jul 02, 2018 9:48 pm
Forum: RTL-SDR Discussion
Topic: Weak reception when in movement!
Replies: 11
Views: 5606

Re: Weak reception when in movement!

ligghts, a car radio FM receiver has some specific signal processing functions that "hide" the loss of signal from the Rayleigh path level distribution (or variations). The dongle software has none of these functions *** (a and b; see below). It is important to distinguish between multipath with sma...
by Brightnoise
Mon Feb 19, 2018 12:49 am
Forum: RTL-SDR Discussion
Topic: Raw digital output from usb dongle
Replies: 8
Views: 5863

Re: Raw digital output from usb dongle

The PLL settling with the proposed component values from the Rafael application: see figure attached. This is the response to a frequency step (t_step at 10 microseconds). When the initial step was 1 MHz then the final error can be obtained as ratio from the default factor "one". For a frequency swe...
by Brightnoise
Mon Feb 19, 2018 12:29 am
Forum: RTL-SDR Discussion
Topic: Raw digital output from usb dongle
Replies: 8
Views: 5863

Re: Raw digital output from usb dongle

And then the speed of the PLL. The PLL-filter is not integrated in this chip. The filter in the standard application is pole at 1800 Ohm and 330 pF, zero at 1800 Ohm and 6800 pF. The frequencies belonging to these values are given in the plot below. The unity-gain for the PLL is 100 kHz and the sett...
by Brightnoise
Mon Feb 19, 2018 12:13 am
Forum: RTL-SDR Discussion
Topic: Raw digital output from usb dongle
Replies: 8
Views: 5863

Re: Raw digital output from usb dongle

The question was: How does one determine how much PLL settling time is needed after each frequency jump? I assume the IQ data is mostly garbage until after the PLL + internal filter settling time. My answer was detailed because I am curious how fast a well-designed spectrum analyser with the RTL-Don...
by Brightnoise
Fri Feb 16, 2018 5:32 pm
Forum: RTL-SDR Discussion
Topic: Raw digital output from usb dongle
Replies: 8
Views: 5863

Re: Raw digital output from usb dongle

PLL settling time in good designs is ten times the period duration of the reference frequency. (Frequency error smaller than 1 % of initial frequency step, within one octave). In the RTL front-end chip the VCO is running in the GHz range, with a max/min frequency ratio for that VCO of preferably sli...
by Brightnoise
Thu Feb 15, 2018 3:11 pm
Forum: RTL-SDR Discussion
Topic: Raw digital output from usb dongle
Replies: 8
Views: 5863

Re: Raw digital output from usb dongle

Working now! RTL-SDR dongle panorama needs these files (see figure below) in one and the same subdirectory; that is all. Download from: https://sourceforge.net/projects/guiforrtlpower/ and follow the instructions. 64 and 32 bits versions are available. Program start: RTLPAN.EXE And as expected: scan...
by Brightnoise
Thu Feb 15, 2018 2:18 pm
Forum: RTL-SDR Discussion
Topic: Raw digital output from usb dongle
Replies: 8
Views: 5863

Re: Raw digital output from usb dongle

The complete spectrum on the screen is also my wish. The AD converter bandwidth is 14.4 MHz (half sample frequency). The filters in the baseband chip however limit the maximum BW to slightly above 2 MHz wide (baseband I&Q signal in frequency range zero plus and minus 1 MHz). Using the dongle as a sp...
by Brightnoise
Tue Jan 30, 2018 11:13 pm
Forum: RTL-SDR Discussion
Topic: The matching transformer and toride T37-43 & DIRECT SAMPLING
Replies: 4
Views: 8384

Direct sampling dongle V3 modification; input impedance of RTL2832

Reading these posts I decided to remove the original transformer in my dongle (recent production; version V3) and to measure the input impedance of the baseband chip. Not with an impedance meter (overload!), but by adding and removing outside series and parallel impedances; complex and real. And thi...