Electronics > RF, Microwave, Ham Radio

SDR - various uses including spectrum analyzer

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Electro Fan:
I'm starting to play with SDR in various forms.

This might have been posted elsewhere but I didn't see it when doing a (maybe too quick) search here:

Just curious to get comments on this, including whether anyone has seen similar apps for iPhones?

Apple devices like the iPad and iPhone do not have USB interfaces! :(


--- Quote from: Electro Fan on January 21, 2016, 07:36:03 pm ---I'm starting to play with SDR in various forms.

--- End quote ---

Not android, not tablets, definitely not iPhone, probably RPi but I haven't tried: you might be interested in https://entertaininghacks.wordpress.com/tag/sdr/

I've more results and will publish the scripts, but I've not yet had time to do it. With luck I'll have some time in the next few days.

In terms of using RTLSDRs as test equipment, science oriented users should learn about the "rtl_power" binary that comes with the driver -which can do quantitative measurement and write the results to a file for later analysis with the tool of your choice- or you can use the rtl_sdr binary and a pipe or fifo .. save the raw data to a file or pipe it to another tool in real time.

Also, the Linrad SDR program ( http://sm5bsz.com) is worth looking at because it has lots of test-related functionality and also supports a great deal of fine-grained configuration including the unique, as far as I know, ability to calibrate the dongle to parts per billion -assuming you can get really good stability out of it, that's an area where they vary a fair amount from model to model.

The calibrated noise figure device mentioned I think uses a modified library - which I think Linrad can also use if they are found. I have more info on that somewhere, I will have to dig it up.

I have two dongles - the ones I use the most, which both have very good frequency accuracy. One is under 1 ppm. It doesnt have a TCXO, it has not been modified in any way, it was super cheap, it just came that way. Its very stable. It runs quite cool, it never gets hot, maybe thats part of the reason why. Also it has a flat SMT crystal. (I think the can crystals are always way way off. Perhaps they are grade B from some other factory production line.)

One suggestion that seemed to work to make all dongles more stable- SM5BSZ found, was putting the bare dongle, removed from its case, in a closed container with a bunch of clean sand around it.

I have used an SDR-dongle for sniffing whether the external MCU oscillator is running or not, and whether the frequency is way out of normal range. Using an oscilloscope disturbed the circuit too much, so sniffing the oscillator with the SDR was a good choice. I took an oscilloscope probe and attached a small coil made of 10 turns to the probe. Hooked the probe to SDR using a BNC/SMA-adapter, placed the coil near the oscillator and the used the SDR-software to see the oscillator's frequency and status.


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