Архив за 14.06.2018

RTL-SDR Discussion • Re: RTL-SDR’s in an outdoor box

USB 2.0 max cable length is a bit over 15 ft, so depending on the actual distance you may either need an extender cable, or one or more USB hubs. Since the RTL-SDR dongles can draw well over 300 mA, the last cables that connect to he dongles should be sized accordingly to avoid excessive voltage drop over them.

Do you want separate USB cables for each dongle, or you plan to connect them to a hub up there, and only one USB cable that goes into your computer?

Statistics: Posted by aurgathor — Thu Jun 14, 2018 11:49 pm


Found some interesting signals in the 900Mhz range, possibly utility meters.

Found some interesting signals in the 900Mhz range, possibly utility meters. submitted by /u/Orchestral_Design
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Does this make the RTL-SDR illegal?

On the USA fcc site https://www.fcc.gov/consumers/guides/interception-and-divulgence-radio-communications

It states :

"What about equipment used to intercept radio communications?

The Communications Act prohibits the FCC from authorizing radio scanning equipment that:

  • Can receive transmissions in the frequencies allocated to domestic cellular services.
  • Can readily be altered by the user to intercept cellular communications.
  • May be modified to convert digital transmissions to analog voice audio.

It is illegal to manufacture, import, sell or lease such unauthorized equipment in the United States."

An rtl-sdr can "receive transmissions in the frequencies allocated to domestic cellular services" or does this mean that the device must inherently be able to decode and process the signal?

submitted by /u/rg422
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Troubleshooting Help • Re: Cant recieve any hf

I was using what rtl-sdr user guide said. You can instead use the screw nut provided with the antenna base to clamp on a long wire antenna that is 5 meters or more in length. I connencted the lenght of wire to the ground nut and washer, then also connected it to the center conduit and had no success.

Statistics: Posted by Blazemaxim — Thu Jun 14, 2018 8:03 pm


Comment on Browsing the UHF Satcom Band via SpyServer by johnney boy

Do not think i would transmit thru or interfere with these US miltary sat comms has the gps location adrf will locate you in a matter of seconds ( has a drug cartel in mexico found to there cost last year , when a attack drome paid them a visit! ) Homeland Security dont mess about.

I’m not able to decode this DMR mototrbo signal.

submitted by /u/Ohmnonymous
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RTL-SDR Discussion • RTL-SDR’s in an outdoor box

Hi. I'm building a new house, and I have the opportunity to mount a few antennas on a horizontal mast on the roof (supported by a very nice heavy duty mast coming through the roof. I am a ham, so I will have a 2m/70cm vertical, a GMRS antenna, a 1090 MHz ADS-B antenna, and a couple discones and maybe some L band patches.

What I was thinking about doing to reduce the feedline length was having a weatherproofed box on the mast that the feedlines would terminate into and maybe have 4-5 RTL-SDR's right there plugged in to one or two powered USB hubs, and then have the USB cables go down into the attic where a NUC running ESXi sits running all the software.

I'd have to provide ventilation and cooling of course. Has anyone done something like this before? Anything I should watch out for?

thx
mike

Statistics: Posted by fresnoboy — Thu Jun 14, 2018 5:05 pm


Comment on Osmocom now accepting Donations by admin

Working fine here on Chrome.

Comment on Running Osmo-FL2K on VMWare Workstation Pro by kapuso

Would you upload the VS2015 projects to build these binaries?

I’ve characterized my homemade filter and eBay amplifier setup for NOAA 137MHz reception!

Hi Everyone,

I’ve had access to a VNA recently so I thought I’d characterize my NOAA 137MHz filter and amplifier setup!

I previously made a post about it here: https://www.reddit.com/r/RTLSDR/comments/8etwd9/.

It’s based on Adam’s design: http://lna4all.blogspot.com/2015/11/diy-137-mhz-wx-sat-bp-filter.

Here is the filter: Front and rear.

Front

Rear

Here is the filter’s response from 50 – 300MHz. The -3dB bandwidth is about 9MHz from 133 – 142MHz. Insertion loss is 3.87dB at 137.5MHz; Adam’s design had an insertion loss of <2dB, but mine isn’t too bad in comparison.

Filter 50 - 300MHz

I am also using an SPF5189Z amplifier that I bought off eBay.

SPF5189Z

Here is the response for the SPF5189Z amplifier from 50 – 300MHz: Nice and flat with about 26dB gain when at 137MHz.

SPF5189Z 50 - 300MHz

SPF5189Z amplifier response from 300KHz – 5GHz:

SPF5189Z 300KHz - 5GHz

Here is the complete filter and amplifier setup:

Filter into SPF5189Z into DVB-T dongle

The amplifier is being powered by the DVB-T dongle. I soldered a PP3 connector onto the USB connector’s 5V and 0V lines. I then soldered another PP3 connector onto the amplifier’s ground and VCC pads. I only used PP3 because I had them lying around, and I don’t recommend using them to connect devices together like this because you need to remember to switch the polarity… or magic smoke appears!!!

Power from dongle:

Crude but working

Here is the response for the filter into amplifier combination, from 50 – 300MHz: Passband gain is 22.8dB. -3dB bandwidth is 8.6MHz from 134.4MHz - 143MHz. Not too shabby.

Filter into SPF5189Z response from 50 - 300MHz

Here is the response for the filter into amplifier combination, from 300KHz – 5GHz:

Filter into SPF5189Z response from 300KHz - 5GHz

Here is an example of an image I’ve captured: My antenna location is rather restrictive so my images don’t have a large latitude range.

NOAA Image

I’m using a V-dipole located in the roof of my shed. I’ll try to characterize that in the coming weeks. :)

Thanks for reading,

Matt

https://twitter.com/noaa_matt

submitted by /u/mechanicalraspberry
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