Архив за 14.07.2018

Comment on KiwiSDR TDoA Direction Finding Now Freely Available for Public Use by RFI EMI GUY

I am blown away by this. Could a downconvertor be used so that VHF and UHF stations can be located? Would it be sufficient to phase lock the LO with GPS derived 10 MHZ clock? I would like to see some local stations with TDOA capability at VHF and above.

Open source alternative to WXtoImg?

Is somebody aware of open source alternatives to WXToImg allowing to convert APT wav files to georeferenced images (i.e. also computing the longitude and latitude of every pixel allowing for map overlays)?

I came across aptdec (https://github.com/csete/aptdec) and APT3000 (http://jthatch.com/APT3000/APT3000.html) but as far as I know, the decoded images are not georeferenced.

Thanks for your help!

submitted by /u/RandomizedAlex
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RF Cable Slip Ring

Hello! I'm working on designing a motorized alt-azimuth mount to position directional antennas. It's conceptually similar to a Radio Telescope.

However, the important part is that it's a mechanism that can rotate continuously. Because of that, if I keep rotating an antenna with a cable attached, it'll get all wound up. To get around this issue, I need a slip ring with some sort of coax pass-through. Although, I'm not a professional on RF cables. Does anyone know what sort of adverse affects using a slip ring for radio signals can have on the signal? What sort of ratings should I look for on a slip ring for this project?

Optimally, this slip ring would be used to receive and transmit on all power and frequency specs that the HackRF One can output natively.

submitted by /u/XeyIer
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Comment on Testing out the New Airspy HF+ Preselector by Max

That sounds reasonable Timmy!

I can’t get my chromebook to work with Linux, is their any browser based programs I could use with my sdr?

submitted by /u/azzman0351
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Comment on Potential Major Security Flaw on HP Laptop Discovered with RTL-SDR by AsianHornet

Interesting bug on some laptops, the DVD drive can sent spikes back onto the 5V line and cause hard drive and USB device premature failure. It took me a while to find but fortunately swapping the drive got rid of it for now.
Didn’t get my data back though 🙁
Wonder if there are signals from the webcam’s microphone as well, if so then SDR might find them when on.

Comment on Cooling the RTL-SDR for Improved Sensitivity by TooManySecrets

Yes, *2 is basically correct. However my IR thermometer seems to show the top of the chip getting hotter.
I wonder if some sort of miniature Peltier module ie the 15*15mm ones (3A 0.7V max) would work?
It wouldn’t need to have that much power though and for this use a simple metal casing would be enough with no fan (probably) needed.

Comment on Testing out the New Airspy HF+ Preselector by Timmy

Usually what is specified as an operating range in a datasheet is what the company who created the part will test and guarantee correct operation during production. There is nothing stopping any company from buying the parts and retesting that they function correctly in the frequency range that they will use in a final product which could be totally outside the specification guaranteed by the part manufacturer. Calibrated test equipment that tests from DC to 3 GHz is more expensive (especially in terms of time) than that which only tests from 100 MHz to 3 GHz. And since their primary market is GSM, WCDMA, and wireless applications up to 3000 MHz, It is cheaper (especially in terms production run testing time) not to validate correct operation below 100 MHz which will only ever account for a tiny fraction of a percentage of their final sales.

Hi all, Is it possible to turn off the waterfall element of the display leaving just the graph?

Hi all, Is it possible to turn off the waterfall element of the display leaving just the graph?

Comment on Testing out the New Airspy HF+ Preselector by Max

Yes, i have seen that but your conclusion gives for granted that they gave a 100 MHz lower limit for no reason. In this case an important disclaimer is missing in the datasheet: “The manufactuter reserves the right to give misleading informations as the reader is supposed to have the knowledge to recognize them”

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