Showing wave form on an oscilloscope.

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snuz2001
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Joined: Mon Aug 26, 2019 6:40 am

Showing wave form on an oscilloscope.

Post by snuz2001 » Mon Aug 26, 2019 7:02 am

Is it possible to show the wave form of a distanced radio station on a scope? Can I for example display NOAA 19 137.1 Mhz on my scope when I receive the satellite transmission?I don't mean the data that is modulated in the wave, but actually the 137.1 Mhz wave form itself.

Thanks.

snn47
Posts: 178
Joined: Tue Dec 27, 2016 11:00 pm

Re: Showing wave form on an oscilloscope.

Post by snn47 » Mon Aug 26, 2019 6:26 pm

Even If your oscilloscope is fast enough to display strong signals at 137 MHz, oscilloscope are quite insensitive compared to the frontend in spectrum analyzer. The easy solution would be to use a receiver with sufficient bandwidth and sensitivity and connect an IF-output to your oscilloscope.

radiolistener
Posts: 47
Joined: Thu Jan 25, 2018 10:48 pm

Re: Showing wave form on an oscilloscope.

Post by radiolistener » Mon Aug 26, 2019 6:27 pm

you already see it on the scope, but it is mixed with other signals and noises which level is higher.

For exampel, -90 dBm means amplitude of 7 uV (micro-Volt).

You can use narrow bandpass filter and about 80 dB amplifier in order to get it visible on oscilloscope. But your oscilloscope should have enough bandwidth.

jamesbr
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Joined: Thu Aug 29, 2019 12:22 pm

Re: Showing wave form on an oscilloscope.

Post by jamesbr » Thu Aug 29, 2019 12:38 pm

I have a local rf link so I have a high signal level available when it transmits. With a small local antenna I should be able to get a -20dbm input. Can I just connect the output to an oscilloscope and see the waveform sampled down a few MHz?

hotpaw2
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Re: Showing wave form on an oscilloscope.

Post by hotpaw2 » Fri Aug 30, 2019 6:04 pm

You would likely need a very narrow band filter, as any antenna would likely pick up a bunch of other, stronger, VHF (and MF, HF and UHF) signals in your environment.

I would be tempted to use a full-duplex SDR to downsample, filter, and then upsample the cleaned up signal for viewing with a high bandwidth oscilloscope.

snuz2001
Posts: 5
Joined: Mon Aug 26, 2019 6:40 am

Re: Showing wave form on an oscilloscope.

Post by snuz2001 » Thu Oct 10, 2019 7:53 am

Thanks for your replies.

1. what is a "full-duplex SDR to downsample"? where do I get it?

2. "You can use narrow bandpass filter and about 80 dB amplifier in order to get it visible on oscilloscope".

How technically can I use it to view a 500 mile far radio source (Noaa transmitter) on my scope? what receiver should I use? Can I use a simple receiver like a baofeng?

3 "The easy solution would be to use a receiver with sufficient bandwidth and sensitivity and connect an IF-output"

What is an IF output? where do I get it and where do I connect it to the receiver?
Do you know any receivers which comes with an rf or IF output so I can connect it directly to the scope and view Noaa's 137.1 Mhz carrier wave?

4. I read a lot about TOA and TDOA with sdr. Is there any way I can compare the arrival time of a distanced signal (like Noaa's) to 2 different antennas with around 50 ns accuracy? if so, how technically it can be done (what equipment, connections, etc.)

Thanks again.

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