SDR - poor man's WWB

Jay Ashworth

Well-Known Member
Another USB Software Defined Radio receiver just went past my eyes, and reminded me I've meant to ask this question:

Is anybody using an SDR to look at the RF spectrum around their stage/studio/shoot, to see if you need to refreq wireless mic receivers/IEM transmitters/wireless comm?

If so, what do you use, do you use a dedicated computer, and what else can you tell us all?
 
I have a feeling someone on the blue room said they were doing just that.  If I can find the thread I'll post a link.
 
Another USB Software Defined Radio receiver just went past my eyes, and reminded me I've meant to ask this question:

Is anybody using an SDR to look at the RF spectrum around their stage/studio/shoot, to see if you need to refreq wireless mic receivers/IEM transmitters/wireless comm?

If so, what do you use, do you use a dedicated computer, and what else can you tell us all?
I use this SDR based project
It is standalone but can be connected to a PC with USB
It's cheap enough that I skipped over all the SDR dongles on Amazon and Ebay and paid the bit extra more for this ready-to-run device
But yes, watching Hams performing spectrum analysis with cheap USB SDR's on Linux is what lead me to search for this.
-Just FYI, the Kali linux distro comes pre configured with SDR libraries and multiple applications devoted to radio scanning. It can actually be used to also receive and listen to the audio not just scan occupancy (It is technically regarded as a "hacker" distribution so be warned -lol)
 
I'm familiar with Kali, but apparently not enough. I'd seen TinySA, but there seem to be a lotta buncha different versions, at markedly different quality levels, both on the Bay and Amawhosis. Any thoughts there?

I've located their wiki, that oughtta help:


Does Kali need to be a spin or packaging, or does the base ISO have those tools baked in?
 
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Yes that is the same Wiki I linked.
Here's the page regarding authentic versions:


And I linked in my previous post to the place where I buy mine.

I am not an expert on Linux distribution installation methods but I watched it get installed into a stock win machine using a USB disk image as a dual-boot and go straight to SDR manipulation without any additional package installation. Now if anything was added to the stock image upon creation of the USB drive then I wouldn't be aware.
It was also 5 years ago at a Ham day at a makerspace I visited with my brother in law.
I have been happily using mt TinySA and NanoVNA (which this SA was derived from) since before the pandemic and have forgotten much of the processes they demonstrated.
 
Another USB Software Defined Radio receiver just went past my eyes, and reminded me I've meant to ask this question:

Is anybody using an SDR to look at the RF spectrum around their stage/studio/shoot, to see if you need to refreq wireless mic receivers/IEM transmitters/wireless comm?

If so, what do you use, do you use a dedicated computer, and what else can you tell us all?
I've been using a USB dongle for 5 or 6 years now, purchased from https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/. With a variety of software I can scan an environment for other usages as well as listen to analog sources. There are many other things that they can be used for, I'll stay on topic.

There is a python scripting application, "RTLSDR Scanner" that will export a file that can be used in WWB. You can find this "app" at https://github.com/EarToEarOak/RTLSDR-Scanner. The USB dongles are relatively noisy comared to something like using a network connection to Shure product but they certainly give you a good idea of the RF environment.

Software can be found for Linux, Windows, and Mac OS (although I don't know whether things have been ported to the M1 or M2 architecture). A quick aside, you can grab weather satellite imagery, imagery from the International Space Station, listen to HAM radio, as well as many other aspects of RF. A good search engine can be your friend, SDR or software defined radio as your criteria.

Happy trails, ya'll...
 
I’ve played with my RTL-SDR, scanning the frequencies around our mics. I did find some frequencies that seemed a bit crowded but nothing that looked like it’d cause a problem. It never occurred to my to try my tinySA. I’ll have to break it out next time we are setting up. Strike is tonight and I’m gonna be too busy doing the TD thing to play radio.

Michael, AKA KF7MBM
 
Keep in mind that there are limitations to all spectrum analyzers, especially less expensive ones. They can display signals that aren't really there. The phantom signals are intermodulation products that are created in the instrument's first RF stages. If you put a 10-20 dB external pad on the antenna input, and the signal disappears rather than drop in level, it's a phantom.

In terms of using one for wireless mics, they'll show holes and spacing, but it doesn't show the mathematical relationship of the carriers that can cause receiver induced intermod products. A program like WWB is far more powerful than a spectrum analyzer by itself.
 
Keep in mind that there are limitations to all spectrum analyzers, especially less expensive ones. They can display signals that aren't really there. The phantom signals are intermodulation products that are created in the instrument's first RF stages. If you put a 10-20 dB external pad on the antenna input, and the signal disappears rather than drop in level, it's a phantom.

In terms of using one for wireless mics, they'll show holes and spacing, but it doesn't show the mathematical relationship of the carriers that can cause receiver induced intermod products. A program like WWB is far more powerful than a spectrum analyzer by itself.
Yeah; I hang out with enough of your counterparts to know most of the limitations; just looking for an excuse to buy one, really. :)

And on the intermod side, what's the thing with tinfoil pans for your handhelds about, again?
 
Yeah; I hang out with enough of your counterparts to know most of the limitations; just looking for an excuse to buy one, really. :)

And on the intermod side, what's the thing with tinfoil pans for your handhelds about, again?
A bit of shielding to prevent all those close proximity transmitters from creating more IM products while the tech is scanning, measuring, and listening to them before deploying them to the artistes.
 
No tinfoil is needed, just spread them out instead of running the transmitters in a pile for testing.

One of the advantages of digital is that the transmitter finals are linear, which makes them less prone to making products.
 

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