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Re: Can the TinySA measure DAB signals?

 

Thanks Tony!

My measurements where made with a of RBW 10KHz - i will measure the signal again with RBW 3KHz, curious if this makes a difference
Re: Can the TinySA measure DAB signals?

 

As can be seen in the screenshots, i have a signal of -70dB which should be low enough - or am i wrong?
Re: Can the TinySA measure DAB signals?

 

I'm using a EasyDAB, which looked fine on a Siglent - and also on the Tiny.
Or i'm overlooking something, or the Tiny is not accurate enough to display sidelobes.
Unfortunately i cannot use the Siglent anymore to cross check

My amplifier is linear - it was formely used for DVB-T
Re: Can the TinySA measure DAB signals?

 

tinySA can discriminate as far as the RBW allows. Be sure that the 3KHz RBW is selected, as in the figure?
Re: No DAB Signals

 

No, but we do have HD Radio here.



73

-Jim
NU0C


On Tue, 19 Oct 2021 21:57:03 -0400
"Mike C." <mg@...> wrote:

Interesting subject, this DAB signal. We don't have it here in the US,
look what we have for leadership.

Mike C.
Re: Schematics for MAX2870

 

I suggest you use MAX2871, which is an improved version of MAX2870, you can refer to this project.
Re: Schematics for MAX2870

 

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Yeah, I read the spec sheet but what I'm looking for are some instructions or users and their comments regarding the ebay item.

Mike C.

On 10/19/2021 10:34 PM, Ray Anderson wrote:

How about:

Ray WB6TPU





On Oct 19, 2021, at 6:29 PM, Mike C. <mg@...> wrote:

?Hi Guys,

Has anybody come up with package information like schematics on the MAX2870? i.e. ebayism # 363099163574

Mike C.
Re: Schematics for MAX2870

 

¿ªÔÆÌåÓý

How about:

Ray WB6TPU





On Oct 19, 2021, at 6:29 PM, Mike C. <mg@...> wrote:

?Hi Guys,

Has anybody come up with package information like schematics on the MAX2870? i.e. ebayism # 363099163574

Mike C.
No DAB Signals

 

Interesting subject, this DAB signal. We don't have it here in the US, look what we have for leadership.

Mike C.
Schematics for MAX2870

 

Hi Guys,

Has anybody come up with package information like schematics on the MAX2870? i.e. ebayism # 363099163574

Mike C.
Re: Can the TinySA measure DAB signals?

 

Be aware the tinySA is feeling the total power (summed power) at the mixer and not just the peak power at one single frequency so if the bandwidth is wide you have to reduce power further than the automatic attenuation will do.
Start by ensuring the peak of the input is below -40dBm (after the internal attenuator) and see if that makes a difference versus -55dBm or -25dBm
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For more info on the tinySA go to https://tinysa.org/wiki/
Re: Can the TinySA measure DAB signals?

 

I don't know how you're generating your OFDM signal, but try looking at it on the TinySA BEFORE you feed it into your transmitter amplifier chain, see how it compares. If your transmitter chain is compressing (non-linearity) your Tx signal in any way then that will reduces it's quality very quickly, no matter how strong it is when it reaches any receivers.
Re: Can the TinySA measure DAB signals?

 

Yours looks clean enough, though there must be something a bit wrong somewhere if 100W's only gets you short distances.

The thing about OFDM is that it requires very linear transmitters, the PAPR (peak to average power ratio) is unfortunately very high, the peaks of the RF carrier are very much higher than the average power, it requires quite a high dynamic range to see the side lobes so not to compress the RF peaks - an OFDM spectrum might look nice and flat but the RF envelope.is far from it, the more OFDM sub carriers you have the higher the PAPR.

Maybe you're right, maybe the TinySA doesn't have the required dynamic range t o show the side lobes ?
Re: Can the TinySA measure DAB signals?

 

[url=https://ibb.co/Qfz4YC1][img]https://i.ibb.co/W6qLBPY/DAB-10-W-20-15-10-30d-Batt.png[/img][/url]
[url=https://ibb.co/Tt1cFNk][img]https://i.ibb.co/ZxSdkbV/DAB-40-W-20-15-10-30-10d-Batt.png[/img][/url]
Re: Can the TinySA measure DAB signals?

 

Hi Mr OneOfEleven,

I am experimenting with a DAB modulator and (DVB-T) power amplifier, and am quite sure that my signal is currently not OK. ( 40W of 100W output power hardly makes a difference, like 200 meters range)
I expected to see (large) shoulders, as i don't have a spectrum mask filter

Screenshot 1: 20dB+20Db+30Db+10Db hardware attenuator, en 10Db on the Tiny. Output power at that moment was 40W
Screenshot 2: 20dB+20Db+30Db+10Db hardware attenuator. Output power at that moment is 10W

I agree that local DAB broadcasters have a very clean signal - but i'm living near a transmitter site, and do not see any shoulders.

From what i've heard, you need a very good spectrum analyzer to see them - but i'm not sure...

DAB_10W_20_15_10_30dBatt.PNG
DAB_40W_20_15_10_30_10dBatt.PNG

Re: Can the TinySA measure DAB signals?

 

The local DAB braodcast transmissions are very clean, the side lobes are very low down. You might see them if you can feed a nice strong DAB signal into the TinySA, so long as you don't overload the it's front end.

This shows what various types of OFDM can achieve (filtered OFDM being the cleanest) ..
Re: Can the TinySA measure DAB signals?

 

Such as here (live DAB radio in the UK) ..
Re: Can the TinySA measure DAB signals?

 

When you say shoulders, wonder what it is you're expecting to see ?

DAB uses OFDM modulation, so the signal will basically be very square indeed, ie vertical sides to it with an ideally flat top.
Can the TinySA measure DAB signals?

 

Hi All,

Did some tried to measure a DAB signal already?
I did, and i'm getting the feeling that the TinySA is not accurate enough to measure the shoulders of this signal.
If this is the case - i fully understand since it has it's limitations... but now i'm not sure.
In my test setup i expected to see shoulders, but i don't see them
Interesting video series on radio design using nanoVNA and tinySA

 

Found this youtube playlist on radio design that combines theory with practical implementation and measurement using the nanoVNA and tinySA



Very good if you ever want to design something yourself!!!
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For more info on the tinySA go to https://tinysa.org/wiki/
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