Author Topic: Moteino & spectrum analyzer  (Read 993 times)

jbeale

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Moteino & spectrum analyzer
« on: April 28, 2016, 02:17:49 AM »
I got an "RF Explorer" (cheap handheld spectrum analyzer) for the 240-960 MHz band and looked at a Moteino running the Tx demo sketch with a RFM69W at 915 MHz. I see the plotted waveform show a peak that progressively moves from 914.7 to 915.2 MHz and tracing out a gaussian shape with a peak near 915.0 MHz. I assume that is some interaction between the analyzer's sweep rate and the Moteino's short Tx packets (sending "123 ABCD...") ?

Video (sorry about the blurry image) 

WhiteHare

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Re: Moteino & spectrum analyzer
« Reply #1 on: April 28, 2016, 09:29:27 AM »
@jbeale Welcome back!

Looks like your RF explorer has a slow sweep!  Based on your description, it also looks like it's displaying an average of the RSSI's it samples over a dwell period before it moves on to the next frequency.  Can you configure it to display the peak RSSI per sweep instead?  It seems like that would make for a more useful display (though displaying both, one curve somehow superimposed upon the other, would be the most useful).  Wouldn't you agree?

perky

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Re: Moteino & spectrum analyzer
« Reply #2 on: April 28, 2016, 05:34:40 PM »
I have one of these, really nice especially when used with the free Touchstone PC software which let's you set the resolution bandwidth RBW manually and hence sweep rate. I believe the on-board display pre-selects a resolution bandwidth for you. You can also see max peak in Touchstone (which you can also set in the RF Explorer display) and get an envelope shape.
Mark.