Help me choose an SDR/Spectrum analysi device: ADALM-PLUTO VS RF Explorer 6G WB+

[glradio]

Greetings to the entire eevblog.com community ! 

I need to purchase a simple electromagnetic spectrum analysis device for use for education purposes.

I have narrowed the list down to these devices:

Analog Device ADALM-PLUTO (about 250€) and RF Explorer 6G WB+ (440€).

I discarded bladeRF 2.0 micro xA4 even though it was my first choice, because it was too expensive, Pluto Plus Sdr because it is a clone without a known manufacturer, HackRF One because Adalm Pluto seems superior, and RF Explorer 6G COMBO+ because I do not need support of frequencies from 50 Khz to 15 Mhz.

I was thinking of buying Adalm Pluto because it is cheaper, has extensive software support, and because portability of the device is not essential and I could achieve it equally with a lightweight laptop.

What advice can you give me on this ?

[Bicurico]

You forgot to mention what you really want to do.

For spectrum analysis, the best bang per buck would be the TinySA Ultra.
Need VNA? Get a NanoVNA.
Want to write your own software to demodulate stuff and want to be able to generate signals? Adalm Pluto might be nice, I think the HackRF might be better, despite being half duplex.
I am not sure that the Adalm Pluto is still being sold?
What frequency range? Do you want to TX or just RX?
Perhaps a simple RTL2832 would be enough?
The cheapest receiver would be the RSP1 clone from AliExpress. Mind you, my first one broke after one month, second is on its way.

As you see, there are so many options, you really need to tell what exactly you want do to.

[arocholl]

It depends on what you actually want to do, RF Explorer is a calibrated measurement instrument whereas Pluto is a general purpose SDR.

[glradio]

You forgot to mention what you really want to do ...

Hello and thank you for your reply.

I knew TinySA up to 960MHz, but I didn't know that an Ultra version had come out that could go up to 6 GHz, seems also 12 GHz !)

The device serves me primarily as a spectrum analyzer: transmitting signals or receiving radio stations would be useful but secondary for my use.

The frequencies I want to receive are up to 6 GHz, in fact all the devices I mentioned in my first post go up to 6 GHz.

Do you think TinySA Ultra is superior to, for example, Pluto Plus SDR when used as a spectrum analyzer with appropriate software such as SATSAGEN to even just SDRSharp ?

[glradio]

It depends on what you actually want to do, RF Explorer is a calibrated measurement instrument whereas Pluto is a general purpose SDR.

Have you had a chance to compare the latest version of RF Explorer 6G with TinySA Ultra ?

From a quick glance it would seem that the latter's firmware options are many more and more advanced.

On the other hand, I could not say about the quality of the hardware components and reception sensitivity because I have never tried them ...

[Bicurico]

I dare to say that the TinySA Ultra beats any other affordable spectrum analyser.

The next step up would be a Siglent SSA3021X-P or a second hand professional device.

Just make sure that the specs meet your needs.

Note that any SDR based device will (normally) show a spectrum with relative values: you won't be able to measure i.e. dBm, but just dB.

While this limitation is good enough to "see" transponders of interest (to which you can then tune the SDR and try to demodulate the signal), it won't be adequate for any measurement.

On the other hand, a spectrum analyzer like the TinySA, TinySA Ultra, RF Explorer, etc., won't be able to demodulate the signal.

Again, it depends on what you really want to do.

Regards,
Vitor

[A.Z.]

just out of curiosity... why did you exclude the RedPitaya ?

https://redpitaya.com/

or maybe you didn't consider it ?

[glradio]

I dare to say that the TinySA Ultra beats any other affordable spectrum analyser.

TinySA Ultra really seems like the best choice in every way considering I don't need to demodulate the signals, thanks for suggesting it !

The next step up would be a Siglent SSA3021X-P or a second hand professional device.

The Siglent SSA3021X-P, however, is limited to 2.1 GHz.

[glradio]

just out of curiosity... why did you exclude the RedPitaya ?

The frequency range of Redpitaya devices seems to be much more limited than those mentioned in this post.

[Bicurico]

Note that RF signals above 2-3GHz start behaving like black magic.

To properly measure them, you need accessories that easily cost as much or more than your budget for the spectrum analyser itself: cables, connectors, attenuators, etc.

I would say that the TinySA Ultra can visualize and prove the existence of given signals at 6-12GHz, but you will have a huge error, attenuation and noise floor. But yes, it is amazing that you can see the signals with such a cheap device.

[ahbushnell]

This might be of interest.  Also other video's on the ADALM PLUTO.

Andy

[glradio]

I would say that the TinySA Ultra can visualize and prove the existence of given signals at 6-12GHz, but you will have a huge error, attenuation and noise floor. But yes, it is amazing that you can see the signals with such a cheap device.

I guess these limitations are also common to the other devices mentioned above ...

Verifying and visualizing the presence of a signal is sufficient and is what I am most interested in.

With the low cost of a TinySA Ultra device, it would not make sense to buy a more expensive device ...

[artag]

Also other video's on the ADALM PLUTO.

e.g. https://www.youtube.com/@jonkraft

Note that there are two versions of the Pluto. The later one can be modified for dual receive / transmit.

[glradio]

Any advice on an antenna that replacing the stock one can improve the performance of TinySA Ultra ?

A user on an official Aliexpress reseller page suggests these antennas:

Socotran SAT-771D VHF 144 430MHz
Gizont gooseneck 5g 698 MHz to 6 GHz
Taoglas TG.55.8113 617 MHz to 5.925 GHz

[Bicurico]

You cannot "improve the performance of the TinySA Ultra" using different antennas.

Different antennas will simply receive the signal in question with a higher gain, especially when the length (or equivalente characteristic) of the antenna is a multiple of the wavelength.

For frequencies above 1GHz, the antennas get shorter and shorter.

When you see an AliExpress offer of an antenna claiming a frequency range from 700MHz up to 6GHz, you can be pretty sure it is a lousy antenna!

Want a "good" antenna, take a look here: https://www.tequipment.net/Rohde-&-Schwarz/HE400/Antennas/

Best approach is to build your own antenna... Often, a simple paperclip, cut to the right length will at least be as good as those chinese antennas.

[radiolistener]

When you see an AliExpress offer of an antenna claiming a frequency range from 700MHz up to 6GHz, you can be pretty sure it is a lousy antenna!

yes, this is just a piece of wire, but it still can be used as antenna for a strong signals, for example if you don’t have a suitable rusty nail or other piece of iron in your shed 

Good resonant antenna has Q about 10 or more, it depends on your requirements for bandwidth. More wide bandwidth leads to a low Q and as result to a low sensitivity. Some short wave magnetic loop antennas have Q up to 2000 and even more, but they have very sharp resonance and very narrow bandwidth (5-10 kHz). This is how it can hear very weak signals despite the fact that it has too small size.

Antenna bandwidth, VSWR and Q-factor are all linked together, so if you increase antenna bandwidth you will lose VSWR or Q and vice versa.

Here is equations:

VSWR = (Q^2 * BW^2 + SQRT( Q^2 * BW^2 * (Q^2 * BW^2 + 4) ) + 2) / 2
or
BW = (VSWR-1) / (Q*SQRT(VSWR))

where
VSWR - worse VSWR within antenna bandwidth interval around center frequency
Q - is Q-factor
BW - is bandwidth relative to a center frequency: BW = bandwidth_in_Hz / center_frequency_Hz


In short, good resonant antenna works as a bandpass filter. It cut-off unwanted frequencies and it allows to get signal-to-noise gain because noise floor drops down. More low bandwidth leads to more noise cut-off and better noise floor, better sensitivity. But if antenna is wide bandwidth it will pass more noise power on it's output and you will have very high noise floor and as result low signal-to-noise ratio and low sensitivity.


Regarding to the original question, I'm not sure if RF Explorer 6G COMBO+ can work as SDR, but at a glance it is marketed as a usual spectrum analyzer. Why do you think that it can work as SDR? There is even no mention about SDR on its site...

If we compare  ADALM-PLUTO with HackRF, then ADALM-PLUTO is obviously better, because it has better dynamic range.

[glradio]

Regarding to the original question, I'm not sure if RF Explorer 6G COMBO+ can work as SDR, but at a glance it is marketed as a usual spectrum analyzer. Why do you think that it can work as SDR? There is even no mention about SDR on its site...

It was an inaccuracy in my initial post: now I have modified the title.

Have you had a chance to compare TinySA Ultra with the other devices in my post, when used as a spectrum analyzer ?

[radiolistener]

I don't have tinySA, so I cannot evaluate it's ability. At a glance tinySA is more convenient for mobile usage. But if you have PC, ADALM-PLUTO will be more flexible and can provide fast realtime spectrum analysis with better dynamic range.

[glradio]

... But if you have PC, ADALM-PLUTO will be more flexible and can provide fast realtime spectrum analysis with better dynamic range.

Many people here suggest Adalm-Pluto: has anyone had a chance to try this clone ?

It's an advanced version of the original that removes one of its main limitations by adding a gigabit ethernet interface interface.

[radiolistener]

Many people here suggest Adalm-Pluto: has anyone had a chance to try this clone ?

I wanted to buy it, but unfortunately I have no ability due to war.
At a glance it looks good, but since almost all Chinese devices have some pitfalls, this one also can have it's own pros and cons...

[glradio]

At a glance it looks good, but since almost all Chinese devices have some pitfalls, this one also can have it's own pros and cons...

These are the enhancements of Pluto+ over the original version

[Bicurico]

Note that these enhancements are on HW. You would need to develop your own software to benefit from them, if I am not mistaken.

[glradio]

Note that these enhancements are on HW. You would need to develop your own software to benefit from them, if I am not mistaken.

There is probably a custom firmware that needs to be loaded by acting on the pcb jumpers, as this part of the video would suggest

[glradio]

Concerning the standard version of Analog Device ADALM-PLUTO, I read from several sources that the real big limitation of this device is the Usb 2.0 interface that prevents to take advantage of the 20 MHz bandwidth of the device (limitation that would be even more evident by unlocking the device to bring it to 6000 MHz and 56 MHz bandwidth).

Does anyone who has tested the device know if these claims are true or just exaggerations ?

[Bicurico]

I own both the Pluto and the HackRF One. I somehow prefer to use the HackRF One. Even for SDR it produces better results.

And yes, USB-2.0 is a limitation on the Pluto. That is why I am of the opinion that the Pluto is great for hackers who are able to program for it. If you transfer the FFT to the CPU running inside the Pluto, then the USB bandwidth would be more than enough to output the sampled sweep data.

But again, for under 200 Euro just get the TinySA Ultra for spectrum analysis and buy an RTL 2832 dongle for demodulation.