Архив за 22.09.2019

Why is my hand wound Unun so much noisier than my Nooelec Unun?

Why is my hand wound Unun so much noisier than my Nooelec Unun? submitted by /u/22shorts
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Comment on KiwiSDR TDoA Direction Finding Now Freely Available for Public Use by Tim Haupt

Directional finding of a phone on a lost hiker is feasible, but certainly not practical for your usual search-and-rescue (SAR) team. As noted, the transmission distance at ground level is limited (depending on terrain, on the order of 1 – 10km). If the receiver was in an aircraft or other high location, this could be perhaps 20km or more.
As a previous posted noted, the frequency ranges used for cell phones starts at 900Mhz, but depending on phone carrier, type of phone and such, the bands used extend to 6Ghz.
In general , the cellular frequency bands are locked out receivers available to the general public – specifically to prevent listening in to conversations. But also, mobile phones incorporate various transmission modes such as frequency hopping, that require specialized receivers to be able to follow.

There is a commercially available device by Harris Corporation, designed for use by law enforcement.
Look for information on Stingray, which is a cell-site simulator. This is used to intercept phone calls, can mimic a cell phone system (pretending to be a legitimate carrier tower), and locate a phone – long as the power is on.
To locate a specific phone, you would need the IMSI, ESN or other identifying information. Otherwise, you would also be picking up the signals from all the other mobile phones in the area, with no chance of distinguishing which was the target.

Tim KI7ZEI

Comment on KiwiSDR TDoA Direction Finding Now Freely Available for Public Use by Tim Haupt

As we are trying to locate a transmitter location, what counts is the output frequency of that transmitter.
As the downconverter is located at the receive end, this does not help at all in finding the location of the transmitter.

Tim KI7ZIE

Comment on SDRSharp Community Plugin Package Now Available by Robert

Hello!
The package works fine for me, no crash so far.
A quick question about R820T driver with decimation – I got the idea behind oversampling/decimation, but output is not as expected.
Driver works fine for 0-decimation. FM radio – 19k RDS tone is where it supposed to be (MPX spectrum). FM sound is normal.
With 2x decimation, things start to get weired, tone is shifted to low frequencies and the 19k tone is now visible at 9.5k
4x-decimation looks actually similar as 2x – the 19k tone is still located at 9,5k, but sound even more muffled.
With 8x decimation the tone gets shifted to 2.4k (I guess 19/8), getting impossible to listen any sound/music.
And: the width of the visible main spectrum (“pyramid” ▲) looks always pretty much the same – I was expecting to get “zoomed in”, just the frequency axis get stretched.
To get the “listen” bandwith next to the “pyramid” it needs to be lowered (f.e. to 20.000 at 8x, with 0x was 200.000) but sound is gone anyway.
Do I have to change another settings to get output/sound with decimation back to normal?
I expect that sound output for NOAA / ISS SSTV is not working well with decimation feature, or?
What about digital signal? Decoding is working normally with decimation enabled in R820T driver?
Thank you very much for help!
(I sent the question already to rtl-sdr.ru team, but no reply yet)

Damage to phone from antennas?

I work pretty frequently with military radios that transmit at around 30-80MHz. They use antennas from simple 7m antennas to GPA antennas. The transmission is usually at either 5W or 50W.

How likely is damage from electronics being close to the antennas? Or is the shielding today good enough to prevent any sort of lasting damage?

submitted by /u/ingenioutor
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Comment on SignalsEverywhere Podcast: Satcom Piracy Interview by Alex

Sounds more like people in remote villages talking to their friends and family to me, although I’m not good at Portuguese

sdl2003 Надо было V.3 покупать. Он работает с веревкой от 10 метров.

1428 пишет:
sdl2003 Надо было V.3 покупать. Он работает с веревкой от 10 метров.
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Широкополосный приёмник из DVB донгла - Страница #575

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Подскажите, неужели у всех такая плохая чувствительность на КВ? На веревку 10м поймал единственную мощную китайскую стан…

TarLink пишет:
Подскажите, неужели у всех такая плохая чувствительность на КВ? На веревку 10м поймал единственную мощную китайскую станцию. Еле слышно...и все. RTL-SDR USB Tuner Receiver/ R820T + 8232 RTL-SDR V3 , ...
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Широкополосный приёмник из DVB донгла - Страница #575

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неужели у всех такая плохая чувствительность на КВ? У RTL-SDR V3 нормальная. Многое от антенны зависит…

RANET пишет:
неужели у всех такая плохая чувствительность на КВ? У RTL-SDR V3 нормальная. Многое от антенны зависит...
читать полностью...
Широкополосный приёмник из DVB донгла - Страница #575

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Подскажите, неужели у всех такая плохая чувствительность на КВ? На веревку 10м поймал единственную мощную китайскую стан…

sdl2003 пишет:
Подскажите, неужели у всех такая плохая чувствительность на КВ? На веревку 10м поймал единственную мощную китайскую станцию. Еле слышно...и все. RTL-SDR USB Tuner Receiver/ R820T + 8232
читать полностью...
Широкополосный приёмник из DVB донгла - Страница #575

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