Scan LOW Synch

attachment:tinySA-LOW-Output.jpg

Since the firmware version 1.1-94 you have a trigger pulse output on SMA connector HIGH, when you set LOW to Output, see the screen shot to the right.

If the electric load is high (>22KOhm) the amplitude is about 3 V.

This trigger pulse is used to synchronize an oscilloscope sweep scan, in order to get a steady display.

The tinySA LOW output level is level normalized over the whole 0-350 MHz output range but only if the chosen output level is -15dBm or lower.

Then the amplitude deviation is about +/- 1 dB.

When you want to sweep, tap on SWEEP.

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attachment:tinySA-LOW-SweepMode.jpg

Application DSO Frequency Response

My first idea to test this new feature was to measure my Digital Storage Oscilloscope (DSO) frequency response, a Hantek DSO5072P.

If I want to test the frequency response of channel 1, the LOW output is connected via coax cable 50 Ohm to the DSO channel 1, terminated with a 50 Ohm load.

Channel 2 is connected with a DSO probe to output HIGH, in order to trigger the scan. The connection was made with a PCB edge SMA female plug.

In this case the sweep scan width was set to 150 MHz.

The sweep time was set to 1.5 s.

See below the scan of Channel 1.

attachment:tinySA_Hantek5072_Frequency_Response_CH1.jpg

The acquire mode was set to peak in order to just show the envelope.

You see 2 curves symmetric to the horizontal axis. Usually you take care about the upper half only.

The blue trace (Channel 2) shows the trigger pulse.

Note: Above 70 MHz the curve shows some overshoot, because of tuning the amplifier.

The next screen shot shows the frequency response of Channel 2 (not tuned).

attachment:tinySA_Hantek5072_Frequency_Response_CH2.jpg

So make the DSO setup easier, following the setup parameters.

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tinySA(see the screen shots on top of the page):

Menu->CONFIG->MODE: LOW out

LEVEL: -15dBm

Tap on: SWEEP(=ON)

SWEEP SPAN: 150MHz

SWEEP TIME: 1.5s

DSO:

Utility: Page 2/3: Time set to actual time

Acquire: Mode: Peak, so you see the envelope only

Display: Page 2/2, Grid Intensity: 15, Wave Intensity: 12

Horizontal: tune the trigger point to the left border.

Measuring with 10:1 DSO probe

I was curious to know how good the DSO 10:1 probe (200 MHz) is, in comparison to the terminated 50 Ohm coax cable.

First the measurement setup.

The HIGH output has a 3 V synch pulse for triggering the DSO.

The LOW (Sweep) frequency output is terminated with 2 SMD 0805 100 Ohm resistors in parallel.

The tip of the probe is connected to a SMA PCB connector. The Ground of the probe is connected via spring to the SMA PCB connector.

attachment:tinySA_Hantek5072_Frequency_Response_CH1_IMG_2817.jpg

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Below is the DSO screen shot with the 0 - 150 MHz sweep.

attachment:tinySA_Hantek5072_Frequency_Response_CH1_probe.jpg

Whe I compare this screen shot with the first one (coax cable connection) I see 2 deviations.

The noise of the signal is probably caused by 10 times more amplification in the DSO (2mV/div to 20 mV/div).

The frequency response is a little bit more flat, I do not know why.

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-- RudolfReuter 2021-02-24 16:13:29


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