Poll: Are You Interested in Roadtesting a USB Software-Defined Radio Platform?

Forgot to mention one important detail. To receive any antenna could be plugged and worse that can happen is that you will get poor performance. When it comes to transmitting though, you just can't plug anything to it.

I have a LimeSDR, which is a similar but slightly different product, so can maybe help answer some generic questions.

Most of the high-end SDR boards are not designed for directly connecting an antenna for working the airwaves, although it is possible to do that, and people have done that successfully. They are missing bits that a normal receiver/transceiver would have.

The input/output is 50 ohm impedance, so any potential antenna would ideally need to be matched to that. However, depending on what's the aim, it may also need any of these:

Low noise amplifier (rx), power amplifier (tx), filters, attenuator, even lightning protection. Without these, it may not even perform as well as a non-SDR receiver. For example, if there is a high power transmitter nearby, that will overload the SDR unless there's a filter at a minimum. Any typical decent receiver will have that, even if it's a non-SDR receiver.

(EDIT: The long connector at the side is possibly (I've not checked the documentation) for that purpose, i.e. to control all the extra bits that may be required when integrated into a system like a radio receiver say).

This board is a module, but not necessarily for direct connection to the antenna, without all the bits in-between.

Also, for some bands (e.g. HF if it was desired, although this is very overkill for that) frequency translation would be needed.

There are several topologies for SDR, one popular one a couple of decades ago (since high-speed high resolution ADCs were not available) was to always have a mixer stage preceding the SDR portion, i.e. the SDR would accept the intermediate frequency (IF) (in other words, an SDR radio would look like a non-SDR radio apart from everything from IF stage onward). That's become less necessary with these high-end SDRs, but might still be required.

The very high bandwidth makes this useful for test equipment too (e.g. simulate new radio protocols, act as BLE sniffers, real-time spectral analysis etc). It makes an extremely powerful signal generator for RF too, since anything can be created/modulated.

Even for non-radio use, SDR can be an extremely useful/universal tool. From my perspective the LimeSDR is let down by poor software though : ( And although GNU radio works with Lime theoretically, it's quite tough to get it working always.. LimeSDR also has a simpler software toolset, but that was missing features (might be more feature-rich nowadays).

Product is not new, it is similar to the B200. You can get dirty cheap monopoles to plug into it.

On initial discovery I found this RoadTest poll of interest. The picture of the product is deceiving.  According to manufactures docs, The USRP B205mini-i delivers a 1×1 SDR/cognitive radio in the size of a business card. It is just a little guy!

GL Gough Lui makes reference to antennas in his post and that piqued my interest. To conduct a review of this product the reviewer will need some resources. I suggest if the product becomes a candidate for RoadTest the following list of materials be included, if not reviewers need to be aware you may have some purchases to make if you are not an SDR dabbler already.

• Enclosure
• External power supply
• Antenna(s)

I was unable to locates schematics for the B205mini-i, the links produced a B200 only, even though they indicated the mini device. I'm wondering if the product is fairly new? I also found little information on antenna requirements. I had hoped there was a kit page that provided suggestions. I had no luck on the antenna side. Maybe if someone else takes up the baton for research on this product they can post their findings.

Here are some links I recorded on the product. I suggest, if researchers find other links they can post them to assist possible reviewers.

• https://www.ettus.com/all-products/USRP-B205mini-i/
• https://kb.ettus.com/B200/B210/B200mini/B205mini_Getting_Started_Guides
• https://kb.ettus.com/B200/B210/B200mini/B205mini

It seems that will be nice to see how it works compared to HackRF.

cghaba - Seeing as this one only has one antenna port, no, the antenna isn't "software defined" and nor is this single unit on its own capable of MIMO-style beamforming. But because it does support 10Mhz reference clock input, perhaps phase coherency can be achieved somehow across multiple units in which case, with careful geometrical arrangement of antennas and phasing of the generating signals you could potentially have an electrically-steerable beam.

- Gough

baldengineer - perhaps good for studying or DIYing 5GHz-band stuff - e.g. Wi-Fi (not 80MHz/160MHz 802.11ac/ax), radar or proprietary FHSS applications. Otherwise, could make a good "on the air" test of C-band satellite LNBs with DVB-S emissions in the 3.5-4.2GHz range. But you're right - high frequencies are less often used and more difficult to cope with, so perhaps having it would make it more amenable to use by amateurs.

- Gough

The SDR knowledge well is both deep and wide. A far cry from the SDR USB dongle I dabbled with a few years ago. Bring it on.

Thanks, I looked up I Q sampling,have a much better idea of whats going on, My mind is still stuck on superheterodyne.

Very interesting, would rather like to play with this one, with GNU-Radio, OpenWebRX, etc.