Σάββατο, 25 Νοεμβρίου 2017

New SDR HF decoding hardware platform and new record!

   For quite a few months now, my SDR based reporter was not working due to multiple hardware failures. The bigger problem in remote areas where little noise exists, are thunder-strikes! We got lot's of them in the place the receiver is located, at KM07 grid square. Also several software limitations were requiring manual configuration of the decoding software after each reboot of the decoding server, that happens quite often due to power grid failures. A total solution to the problem had to be implemented that will cover all possible scenarios  (besides nuclear threat).
  So a new desktop computer had to be purchased to replace the power efficient i5 laptop. After installing all required software, I figured that the E3-1240 XEON processor is more than enough for Quad band (4x192KHz) spectrum demodulation and decoding of CW and FT8/JT65/JT9 spots.
The RF front end of the SDR is nothing more than an AD8138 ADC driver, driven by a MAR6 LNA, driving the AD9864 ADC's. From there on 4 Rx chains are created on the FPGA to achieve instantaneous Quad band coverage. The software part is kindly provided by OL5Q. However in order to achieve both CW and other digital modes demodulation, the IQ data has to be shared among other software in Windows. This is achieved by CWSL software, that is open source!

  An issue I was facing with ExtIO_CWSL.dll was that each time it started with HDSDR you have to select the band that it will use, and there is no configuration file, or any other method to pre-select the band you desire. This makes it difficult to auto-start multiple instances of HDSDR, one for each band.
   As an original Radio Amateur, while not having any C/C++ programming skills, I had to find a solution to this. Since the source was available I modified the variable storing the band selection in the dll, so each time it starts with a pre-selected band. I had to build 4 versions of the DLL, one for each band, but this wasn't such an issue. Now I can have 4 instances of HDSDR, connected to WSJT-X via a virtual audio card and a virtual com port to select frequency, AUTO starting!!!
This setup, including the irreplaceable Skimmer Server which by the way is the only ham software that I have purchase and deserves every penny, has placed me to the top 5 of the world's skimmers as reported by PSKreporter.info

Παρασκευή, 14 Ιουλίου 2017

Extreme Trodo Ducting [TR] 704Km at 1090MHz reception over Ionian Sea [Greece-Italy]

Good news today, be broke our previous ADS-B range reception record and received an airplane 380 Nautical Miles away with just an RTL-SDR!!! Also we hit a new record from Tropo Ducting conditions for 2017 and a new high temperature record at our local weather station! Good TR DX fellow hams!

Δευτέρα, 27 Μαρτίου 2017

LimeSDR review

The latest addition to my SDR collection is the LimeSDR.
Much promising in paper, will it prove as much in real life? For start it has failed my expectations.

After a dream came true with the purchase of my first USRP1 SDR from olifantasia himself at 2011 CCCamp, 6 years have almost passed, and technology in Software Defined Radio hasn't evolved as much as I've been expecting. Prices have dropped, but a good design is always well paid.
In the name of SDR god, I've sacrificed thousands of Euros and Dollars since then. In daughterboards like the WBX, SBX, RFX400/900/1800, LFRX, TVRX etc, then when the first USB 3 SDR came available, the USRP B200 it was time for an upgrade. Back then I was amazed with the tiny Analog Devices RFIC and it's performance, however the cost. It was the time when the first crowd funded SDR projects appeared, BladeRF was out, and Ettus decided to build the first product without a case for the lower end market. I think there was not much profit for them in the B200, but a nice company like Ettus has to offer a broad selection of products for every use, even under the umbrella of NI.  I still use my B200 as a reference SDR for comparing with other SDR's.

Of course I had to honor Michael Ossmann who produced the first full open source SDR, HackRF. The idea of using cheap commodity components and engineering a clever design is much closer to my point of view, however HackRF's main drawback is the 8-bit ADC that proves a game stopper. 

I couldn't miss of course the Rad1o, which was more than a reason for flying again with my tent and backpack to Berlin, this time well prepared! Rad1o's concept was also clever, but I was expecting greater acceptance by the community and more software for it. If they had find a way to make it a product, it would be well noted.

Of course I should get a BladeRF with the Up conversion card for ham use, multiple RTL-SDR's for AIS, ADSB and general use, rtlsdr.com's RTL-SDR with a better clock and LNA out, USRP N200, N210 for high bandwidth applications and now the LimeSDR!

I've been following Limemicro since the beginning, and I generally like their philosophy. They are taking one step at a time and have achieved great things in little time, in a hostile environment like the wireless chip industry. This time they promised something big! A sub $300 SDR that has nothing to be jealous of his big old brothers. Did they make it for real?

The first impression is beyond expectations. A very nice packed product that has all that requires for a successful crowdfunding campaign. However the first thing you notice when you plug it in, is that it becomes hot, real HOT! To convince you I made a small video with my FLIR thermal camera:

Another user has noticed that the Altera FPGA works at 74C! The strange thing is that the heat comes out even if the board is idle, which makes me wonder if there is any power saving strategy implemented at all.

In almost all urban environments, most of the RF noise comes from FM radio stations, unless you are from Norway where they switched to DAB. In Greece however where the RF spectrum is relaxedly regulated, most FM band radio stations are using excessively high power for their range that ends up in noise interference. So using a very very big signal that is everywhere, is a good start for checking if a radio device works. And guess what, LimeSDR did not work!
For start I though that there was something bad with my board, maybe a production fault or something similar, it didn't cross my mind that this was by design! I've checked all the antenna ports, all sort of cables, connectors and antennas before I started googling for it. And here it was, many users had the very same issue, LimeSDR deafness. Yes, it was real, I had to use the soldering gun to remove a coil form my new baby. The surgery had to be done, because it was born deaf.
 Then I realized that this was another over-funded and well designed campaign that had used well known marketing practices to gain interest. My problem was not that I didn't get what was promised, because as an engineer I have learn that specs most of the times differ from paper to real life, but this poor performance would affect the opinion of thousands not so expert backers that need something that works, and keep them back form funding another SDR in the future!

Let's hope that any further issues will be resolved via software or soft-hardware (FPGA) upgrades and that MyriadRF will continue supporting this overrated board.

Δευτέρα, 23 Ιανουαρίου 2017

Quad antenna ADSB software receiver

   Finally, after many months of downtime due to a thunderstorm that actually fried most of the pcb's, the ADSB receiver is back online.
Feeding to fr24.com and Flightaware it only takes an underutilized ARM SBC and a USB HUB that costs more than the SBC to decode all this information and transport it to the community network.
A few years ago it all sounded unfeasible, but economies of scale made their miracle and the major expense has moved from electronics to aerials. Indeed the antennas, box and mast cost way more than the actual SDR decoding device.