Архив за 21.01.2018

Off-Topic • Re: NSA Tracking of powered down cellphones and other wireless devices

Have a look at back scatter, here's a simple example with RTL-SDRs https://www.rtl-sdr.com/rtl-sdr-based-w ... r-network/. Could be possible that each phone would have a unique backscatter.

I think more likely is that if the battery isn't removed then the phone probably isn't fully powered down, and is still transmitting something. Probably via NSA malware.

Statistics: Posted by rtlsdrblog — Sun Jan 21, 2018 11:57 pm

Troubleshooting Help • Re: Raspberry pi 2b: FR24feed + rtl-sdr tcp

Seems there was a bug in some drivers that caused that bias tee error. Either upgrading the to latest (not on package managers yet I think), or using even older drivers fixes it.

Statistics: Posted by rtlsdrblog — Sun Jan 21, 2018 11:51 pm

Troubleshooting Help • Re: Big problem whit SDR# software

EvertHarley wrote:
Sun Jan 21, 2018 2:02 pm
I have some problems too with my RTL SDR it comes with 0.30 kHz up to 1.7 ghz......... purchased in China

My system is a HP LPT EliteBook Intel i7 cpu / 8 gb ram / video Intel R Graphics 4000/ and works under Windows 10 pro

The problem is that the software doesn't recocnise the SDR and it says "no device selected" only in dropbox when i sellect Funcube Dongle Pro+ it works but there's no reception or the receiver has no signals :(

Please help !!

Thank you
Did you follow the quickstart guide at www.rtl-sdr.com/QSG?

Statistics: Posted by rtlsdrblog — Sun Jan 21, 2018 11:49 pm

RTL-SDR Discussion • Re: Level meter defaults

The answer is already in this forum. See viewtopic.php?f=1&t=368

Statistics: Posted by Brightnoise — Sun Jan 21, 2018 11:11 pm

RTL-SDR Discussion • Re: Regenerative preselection to improve HF dynamic range?

Mfj sell something called a active antenna model number 1020c . It is a Amplified preselector , the range of the gain is -10db to +10db . it works well with the V3 dongle . Frequency on it is from 300khz to 40khz . The price is just under $100.00 . You can find them used on Ebay for less .

Statistics: Posted by P-40 Warhawk — Sun Jan 21, 2018 10:45 pm

RTL-SDR Discussion • 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 at 140 kHz, and following that first-order slope further. The feedforward gain can be driven up to a Q of 1000. My experience is that regenerative feedback can not be used far over Q-factor 1000 for stability reasons. So the practical selectivity will be a first-order system with top BW of 7 kHz and an effective selectivity of 35 dB for 7205 kHz; I assume that is your fear-frequency. The problem is that with Q-magnification also the noise in the pass-band goes up: good design is a prerequisite. Finally, also the IM3 is multiplied. Succes when you continue with this idea.

Statistics: Posted by Brightnoise — Sun Jan 21, 2018 10:03 pm

RTL-SDR Discussion • 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 frequency of this conversion process is on the same IF-frequency but the 90 degrees offset is just the other direction, or minus 90 degrees shift. In popular words: positive and negative frequencies). These two signals are fed to the AD-converters. The combination in the digital baseband chip takes care for the specified image rejection. This is again a complex frequency shift, decimation and finally IF low-pass filters for the selectivity. The analog phase errors (not exact 90 degrees) are the IQ-errors (and the correction system in the baseband chip can, for a large part, even correct phase and amplitude errors made in the input chip). Thats how it works.

Statistics: Posted by Brightnoise — Sun Jan 21, 2018 9:36 pm

Comment on Leif Compares the Airspy HF+ with the Airspy+Spyverter Combo by Evelyn

I don’t have my unit yet, but I plan on upgrading the firmware once it arrives, an extra 6dB with a firmware upgrade. It will not fix your VHF problem, but at least you will have worked out how to upgrade the firmware, once a new firmware with a fix is released. I know that the TETRA image in the Air Band has been mentioned and a new firmware is being worked on “if the gain of the antenna in higher bands is better than the tuned band, the current firmware thinks it’s OK to increase the gain – expect an update” (was said ~9 days ago).

“Summary: This release improves the AGC behavior on HF by 6 dB. The impact is better strong signal handling, while still maintaining a nominal sensitivity in other scenarios. Warning: Do not attempt to install this firmware unless you are willing to spend a lot of time debugging your PC, OS and the flashing tools. If not sure, contact a moderator.”

Troubleshooting Help • Re: Raspberry pi 2b: FR24feed + rtl-sdr tcp

Update: installing the alternative Airspy server has "solved" the issue. It is not gone but I do not have this problem when using Airspy.

Statistics: Posted by keukenrol — Sun Jan 21, 2018 9:29 pm

RTL-SDR Discussion • Re: sdr# set up

HDSDR uses an ExtIO_RTLxxxxx.dll and SDR# uses SDRSharp.RTLSDR.dll which is Sharps proprietary driver. Probably been decades since it was last updated.
73 Dave N6DL

Statistics: Posted by dlritter — Sun Jan 21, 2018 9:21 pm

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