Search found 20 matches

by Brightnoise
Wed Jan 24, 2018 10:07 pm
Forum: RTL-SDR Discussion
Topic: New Member Saying Hello.
Replies: 9
Views: 5839

Re: New Member Saying Hello.

Gain setting: with direct sampling in the V3-dongle there is no gain setting. You need to do the gain adjustment in front of the dongle, before the input connector. For example with a carbon or cermet potentiometer. I use 500 Ohm linear and that works fine. Mismatch is not causing problems. (The low...
by Brightnoise
Tue Jan 23, 2018 11:29 pm
Forum: RTL-SDR Discussion
Topic: Excessive current in my RTL-SDR V3 dongle and higher temperature
Replies: 2
Views: 2276

Re: Excessive current in my RTL-SDR V3 dongle and higher temperature

Yes, negative pulse only results in latch-up! I modified the input diplexer of the dongle and have now lower attenuation in the lower frequency range. I can receive the time signal of Rugby now at 60 kHz, and see a strong signal of DCF77. But this is at the cost of the latch-up problem. Now I know t...
by Brightnoise
Tue Jan 23, 2018 5:07 pm
Forum: RTL-SDR Discussion
Topic: Excessive current in my RTL-SDR V3 dongle and higher temperature
Replies: 2
Views: 2276

Excessive current in my RTL-SDR V3 dongle and higher temperature

My dongle is sometimes drawing excessive current and I found one reason for that. Observed currents at normal operation: - Connect to USB 110 mA. - Start RTL-Sharp in direct sampling mode 153 mA. - Start RTL-Sharp in quadrature mode 281 mA. - Closing RTL-Sharp: current goes down to 85 mA. Faulty mod...
by Brightnoise
Tue Jan 23, 2018 2:27 pm
Forum: RTL-SDR Discussion
Topic: New Member Saying Hello.
Replies: 9
Views: 5839

Re: New Member Saying Hello.

Welcome. I own more dongles and I recommend you, based on my experience, to buy the already modified RTL-SDR V3. See webshop of rtl-sdr. Than you have a stable oscillator, not drifting away from the indicated frequency. And further you have already the option to use 500 kHz to 14 MHz in direct-sampl...
by Brightnoise
Mon Jan 22, 2018 10:21 am
Forum: RTL-SDR Discussion
Topic: How does the image rejection filter in the R820T(2) work?
Replies: 6
Views: 5713

Re: How does the image rejection filter in the R820T(2) work?

Correction: the above explanation is valid for the E4000 tuner. The used tuner R820T has an analog combination filter in the output of the two parallel analog mixers. After this "all-pass 90-degrees combination filter" the SINGLE ended IF signal is fed to ONE of the two AD-converters. As designer I ...
by Brightnoise
Sun Jan 21, 2018 11:11 pm
Forum: RTL-SDR Discussion
Topic: Level meter defaults
Replies: 1
Views: 1568

Re: Level meter defaults

The answer is already in this forum. See https://www.rtl-sdr.com/forum/viewtopic.php?f=1&t=368 So far, this modification does not work at all. It gives only an other color in the waterfall display. Also, there is still no option for "Level meter default ON" and a value for the averaging time. Does s...
by Brightnoise
Sun Jan 21, 2018 10:03 pm
Forum: RTL-SDR Discussion
Topic: Regenerative preselection to improve HF dynamic range?
Replies: 2
Views: 3122

Re: Regenerative preselection to improve HF dynamic range?

This can be used for sure. The basic calculation is as follows: starting with an LC-filter with LOADED (antenna is connected!) Q-factor (quality factor) of 100 makes a -3dB top bandwidth of 70 kHz. The attenuation for off-frequency signals is -3 dB at (+ and -) 35 kHz, -6 dB at 70 kHz offset, -12 dB...
by Brightnoise
Sun Jan 21, 2018 9:36 pm
Forum: RTL-SDR Discussion
Topic: How does the image rejection filter in the R820T(2) work?
Replies: 6
Views: 5713

Re: How does the image rejection filter in the R820T(2) work?

There is a valid specification for image rejection. The LO generates two signals with about 90 degrees phase difference. This is called a complex oscillator signal. The antenna input signal is converted in TWO parallel mixers and generates TWO IF-signals with also 90 degrees phase shift. (The image ...
by Brightnoise
Sun Jan 21, 2018 8:32 pm
Forum: Off-Topic
Topic: NI-MH battery monitor design. Any obvious errors?
Replies: 1
Views: 2316

Re: NI-MH battery monitor design. Any obvious errors?

Apart from the battery polarity, and the value of the 100k (should be 33k): this circuit will probably work, but the current consumption of this indicator circuit is more than 10 mA. So this is not really what you want, I assume. I have same problem: many battery packs in use. My workaround: monitor...
by Brightnoise
Sun Jan 21, 2018 11:51 am
Forum: RTL-SDR Discussion
Topic: Level meter defaults
Replies: 1
Views: 1568

Level meter defaults

RTL-SDR starts-up with all the settings as active when closing the program (offset frequency, ppm's, frequency etc.). Except for the level meter. So the first thing after start-up is always to enable the level indicator and to set the averaging time to one second. I can't find any program line in th...