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178eur for a niche RF product in a machined shell is not too outrageous.
More than what I' d be willing to pay for a hobby device, but perfectly ok if you are not comfortable homebrewimg one from junkbox parts and ebay modules like I did for my 50-5000MHz downconverter.

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Roger,

I did not know that. I don't own an SDRplay, but this information certainly made me reconsider buying one!

Perhaps I should not have written "all SDR" but "most SDR". i stand corrected!

regards,
Vitor

On Wed, Oct 20, 2021 at 08:50 AM, Vitor Martins Augusto wrote:

However, all SDR devices share one common issue: they cannot be directly used to perform signal level measurements. While they can show the spectrum in dB, you won't find any software that shows the spectrum in dBm. That's because the device has no reference and is not calibrated.

This is why the TinySA is so interesting: it not only renders the spectrum, it allows to do measurements!

The SDRplay SDR products are calibrated in dBm when used with their SDRuno software.? They receive from VLF to 2 GHz. The accuracy is +/- 1 dBm.? As a beta tester for their hardware I can verify that they are accurate for measuring dBm.

Roger

The moRFeus os available at Mouser:

The Adalm Pluto is, like the HackRF One, an SDR based device that works by sampling the input signal.

The spectrum can be shown in frequency domain by processing the sampled data with FFT (Fast Fourrier Transformation).

However, all SDR devices share one common issue: they cannot be directly used to perform signal level measurements. While they can show the spectrum in dB, you won't find any software that shows the spectrum in dBm. That's because the device has no reference and is not calibrated.

This is why the TinySA is so interesting: it not only renders the spectrum, it allows to do measurements!

regards,
Vitor

I could not resist....

Have a look at this video on how you can do the same using one extra tinySA and a cheap eBay mixer module

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With OFDM having a very low average transmitted RF power compared to it's RF peaks, it means to run say 100W's of RF you'll need at least a 1kW PA, probably more. It depends on what the peak to average power ratio is for a typical DAB OFDM carrier is, with DAB having around 2000 sub-carriers the PAPR will unfortunately be high (10 or 20 even), so you'll certainly need a 1 or 2kW PA to provide 100W of DAB signal to the antenna, otherwise you'll destroyed the OFDM signal quality before it reaches the antenna by driving the PA into compression (you must maintain linearity throughout to keep the peaks clean).

Hello,

I just published a new post on my blog on how to use the TinySA in combination with moRFeus (a RF signal down/up-converter):



Regards,
Vitor

@OneOfEleven that's what i'm trying to find out. I guess it's the PA causing the issue, but i'm not sure :)

@Toni Yes i agree

Seems that the Tiny is unfortunately not suitable for analyzing this kind of signals

In a R&S manual i also found a video BW setting that is needed apparently..

I would like to thank you all for the very helpful feedback!

Also consider that, due to the attenuation, you are looking at the upper 30-32 dB of the signal. Perhaps the shoulders are below the noise floor, as several people have indicated.

?ToniC

Well if the modulator is OK, and the PA is OK, then what's left to be at fault ?

For some reason the images are scaled by this board, one post lower you can find the ImgBB URLs.

The modulator should be oke, as it is almost a standard for low power licenced community radio here in NL

I guess your DAB modulator/Tx has a problem if the noise floor is high and flat going out from the OFDM edges (possible RF compression occurring in your RF modulator). Can't tell from your low resolution images what the dB scale is.