$119 to $289
http://rfexplorer.com/touchstone/
$75 or $325
http://usbspectrumanalyzer.com/purchase/
$599
https://www.signalhound.com/products/usb-tg44a/
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look for spec anal:: http://circuit-zone.com/?cat=test_and_measurement pic18f2550 (too slow)
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