Hello All,
Just wondering. Since there is a plethora of nifty EE devices around USB, is there a cheap USB spectum analyzer that runs from, say, something like 150kHz to 1GHz? Something without a screen or anything fancy.
Google brought hits but they were either just audio or WLAN analyzers. Considering the cost of WLAN cards for USB there ought to be something.
Regards, Joerg
It sounds like you're after a complete product, but...
In the September and October 1989 issues of Radio-Electronics, there is an article by Fred Baumgartner on a build-it-yourself spectrum analyzer. Display is to an oscilloscope. The "hard part" is done by a Zenith TV tuner module that converts 50-600 Mhz to 63 MHz (Channel 3) output. This is followed by a TDA7000 FM receiver chip. There is a 555 to generate the swept tuning voltage for the tuner and another oscillator for sync.
If you could get a USB D/A and A/D box, you could use the D/A side (perhaps followed by an amp if the D/A is only 0-5V or similar) to generate the tuning voltage and the A/D side to measure the signal strength. With newer TVs and digital cable boxes, I would guess you could find a tuner that would go up further than 600 Mhz. Finding one that goes down below about 50 MHz might be a problem; perhaps you could adapt a tuner made for shortwave radios.
Matt Roberds
Don't know what you mean by EMC, but if you intend testing for EMC compliance, you might reconsider something hanging out of a PC. You might find it radiates more than the thing you're testing. mike
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Hello Mike,
It can be muffled. The PC itself can sit behind a screen. I even had to do that with a professional $20k class EMC analyzer. It had a flat screen and that radiated like crazy. So it wouldn't be a big deal.
Regards, Joerg
Hello Matt,
Yes.
I have built something along these lines when I was young, to sweep a ham band for activity. But that method is a lot of work and not very accurate. Also it is limited to whatever the tuner can do and these things are often lousy designs when it comes to dynamic range.
Considering all this cheap WLAN stuff there ought to be a USB analyzer out there. Somewhere. Just the absence of a screen, power supply and control knobs would drop the cost significantly.
Regards, Joerg
You could use your audio card to recieve the spectrum data?
Uh ! ? How does this relate to EMC ?
Graham
Hello Graham,
Good question :-)
One scenario I could imagine though would be a controlled down-converter and the sound card would take over as IF stage. SW would do the rest. It won't be stellar in phase noise but for EMC work that rarely matters.
Regards, Joerg
Yes, partially at least. The EMC rules extend to 3GHz and the audio card ends somewhat lower. You could at least mix everything down into the audio range.
Rene
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