The RigExpert Fobos SDR

New SDRs do not come very often, so they are usually worthwhile to check out. The Fobos SDR from RigExpert in Ukraine looked like a novel design with promising features. I got it a little over two weeks ago, and my first impressions did leave some question marks. You can read the blogpost here.

Further testing unfortunately lead to a negative conclusion. This is not the SDR you should buy. At least in its current configuration.

And here is why.

Fobos SDR Is Here! But There Is a Catch...

 Arrived last Friday. The Sunday before I had brought the signal generator with me from the KONG HQ in anticipation of its arrival, since it was unlikely that I could go there this weekend for testing. A 10k run on Saturday got all the attention (and rightly so since I did a PB on the run).

Its blue box with yellow elements such as the five SMA connectors creates a nice tribute to its Ukrainian heritage.

Anyway: I have tested the device. Installation was almost as straight-forward as I expected. I have tested the Fobos SDR with HDSDR 2.80 and 2.81 beta 6, and SDR# (version 1716). It weighs in at 143 grams. Less than one-tenth of the 2-MHz Perseus22.

A few pictures follow. I wonder how they're going to open the box if they need to service it. There is nothing for a screwdriver or torxdriver to connect to. "No serviceable parts inside"?

I should have checked the block diagram more carefully before I bought it.  I was quite surprised that sensitivity on the HF1 and HF2 antenna inputs is pedestrian, to say the least. I measured around -85 dBm on 1000 kHz, actually up to 20 dB worse than other SDRs I have! Now, the block diagram indicates that the LNA only activates in "RF mode", i.e. from 25 MHz and up. So, there is no amplification in the <25 MHz (HF1/HF2) range except the LTC6401 chip.

So, that's where the LNA is hiding

What a strange omission. And why on earth didn't I notice.

It does sample 50 MHz. But the lowest sampling rate is 8 MSPS, not 4 as indicated on their web page. They need to offer lower bandwidths as well. 

It is very light on CPU. Sampling 50 MHz was handled with ease on my four years old HP AMD PC. Recording 50 MHz - well I'm not sure that it was stutter-free, but it didn't crash the application or the PC.

It is quite warm to touch when sampling 50 MHz. 8 MHz was a lot cooler.

Here at home I have no antennas, so it's really quite limited what I can do. And I really need to talk to the people at RigExpert about this. Hopefully, one of the coming weekends I will be able to test how it performs on FM at the KONG HQ, compared with the RSPdx.

More as it happens.

RigExpert FobosSDR

 After some delays over the summer, the FobosSDR from Ukranian company RigExpert is now available. I just ordered mine from wimo.de for EUR 415 (export). GigaParts in Tennessee wants USD 390, but is out of stock as I write this. With a 14-bit ADC resolution, up to 50 MHz sampling rate and two channel direct sampling on the frequency range below 25 MHz, this one may be a very interesting addition to the SDR world. Oh, and it tunes up to 6 GHz. Hardly of interest to the MW DX-er, but there you are.

We will see! When it arrives!

More on the Perseus22 (And a Foggy KONG HQ)

With version 1.2 of the Perseus software out I was hoping to see the implementation of some essential functions for the MW DX-er. However, it was mostly fixes and improvements. I did have a chance to test the WRTH database though. While connection and loading of the database was instant, the results were underwhelming. It seems to me that the WRTH database is far from accurate. One of several examples on the 19-metre band (the only band I checked) is shown below. No it's not Radio Habana Cuba, it's the Voice of America.

Also, MW stations are not listed at all.

There are many databases available. For MW DX-ers a regionally filtered version of MWList would be a lot better. For SW DX-ers I suppose anything but WRTH is better. Sorry to say.

Below is the business end of the Perseus22, namely the back panel. The SMA to BNC pigtails on HF1 and HF2 are tailor-made from Bonito in Germany.

The four channel windows are adjustable in height and width and can be moved around. Below are three of them, HF1, HF2 and VHF1 (the DAB+ band).

After a wet and rather chilly June, we've had dry and warm weather this summer. Coastal areas are exposed to fog though, and yesterday evening it was "thick as peasoup" as we say here. The KONG HQ seen from the beach, 60 metres away.