Using the MSA a Little Differently----Corrected Links

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Using the MSA a Little Differently----Corrected Links

Post by nealmartini » Sat Nov 05, 2011 1:45 am

I screwed up the links in my last posting-Sorry. Please use this posting to view photos.

I have been experimenting with something on my MSA that you all might be interested in trying. Very briefly, I have been using the output of the RFamp (before the final filter) to look at signals in the time domain. Additionally, I am using this same signal as a front end to a software defined radio to get very high resolution spectra and to listen to all kinds of radio signals.

Here are a few examples to demonstrate what I mean:

1. I attached a short wire antenna to the input of the MSA and activated an old remote control for a garage door opener. The remote uses OOSK modulation and the carrier is around 390 MHz. I connected the MSAs RFamp output to a low frequency scope and tuned the MSA to the 390 MHz center frequency. These two pictures show the hookup and scope output. ... 20&dir=asc

See "Remote_Signal_Time_Domain" in photo album

Here is another example of a 300 MHz AM modulated signal connected to the MSA input and the time domain viewing of the RFamp output on a scope.

See "AM_Signal_on_Scope" in photo album

Incidentally, I have the RFamp output hooked up to a coaxial relay so I can switch the RFamp to either the MSA final filter or to an external connector that I hook to a scope.

2. Next I used the MSA RFamp output as a front end to a free downloadable FLEX RADIO software defined radio that runs in a PC. To use this software, you have to convert the RFamp signal to a baseband IQ signal so that it can be input to the PC via the sound card AtoD converter. I assembled an Ensemble II IQ converter (available online for $40)to generate the IQ signals. Basically, the Ensemble II takes the RFamps aprrox 10 MHz bandlimited signal and shifts it near DC. Once the IQ signal is sampled by the PC's sound card, you can use the FLEX RADIO software to get very high resolution spectra. You can also tune your MSA to radio signals and the FLEX RADIO will demodulate things so you can hear the radio broadcasts on your PC.

A few pictures to once again show what I am talking about. First here's an AM signal with 100Hz sine modulation shown in the FLEX RADIO.

See "AM_100Hz" in photo album

That 100 Hz line spacing would be very hard to produce in the MSA alone unless you had a very good final filter. Next here is an FM modulated signal, once again with a 100 Hz sine modulating signal.

See "ReFM_100Hz_1kHzDev" in photo album

Finally, here is a 1350 KHz AM station being listened to on the FLEX RADIO with the MSA as the front end IF signal generator.

See "ESPN_AM1350KHz_SDR" in photo album

Sorry this is so long, but there is alot here. There are more pictures in my photo album at the group site.

I hope you find this interesting.


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