Technical Topics > SDR - Software Defined Radio
RX-888 Unboxing and mini-review
ChrisSmolinski:
Now for VHF/UHF reception.
First, I calibrated the internal ADC clock in the RX-888 (SDR Console has an options window for doing this) by adjusting the PPM value while watching 10 MHz WWV. I found in my case a setting of +0.5 ppm was necessary, obviously your mileage may vary.
There is a separate gain setting for the R820 tuner IC, in my case a setting of 25 worked best, again you will need to experiment to find your ideal setting, based mostly on your antenna. One note - I found the SDR Console did not automatically set this gain in the RX-888 itself when I launched it again, even though the slider was set to 25, I had to adjust it manually to force it to send the setting to the radio.
My VHF/UHF antenna is a discone up 55 ft or so in a tree, with a pre-amp located at the antenna, see this thread: https://www.hfunderground.com/board/index.php/topic,61347.0.html
In the shack this antenna feeds several radios through splitters, which does reduce signal levels somewhat vs just feeding one receiver.
First, here is the RX-888 with no antenna, so you can see the effective bandwidth, about 9 MHz, limited by the R820 tuner IC. There is a noticeable increase in signal levels towards the higher frequencies. This is also apparent when looking at HF signals:
Next looking at local TV channel 8. You can see the ATSC pilot signal at 180.31 MHz. Also up at 186.31 is the pilot for channel 9 which is much further away near Washington DC:
Here's a view of the NOAA Weather Radio stations:
And finally the middle of the FM band:
kris:
A few more notes:
- on my RX, the IC in the top right corner has a heat sink like the one on the left
- integrated circuits and voltage regulators get hot> you can't handle it with your hand
(I think about screwing a small fan housing to the heat sink like in computers, 5V power supply derived from the USB3 socket, holes in the housing would be useful to ensure air exchange)
- flexible white thermal conductive foam on PCB is very delicate and its thin layer tears when inserted into the housing.
When doing this, insert a strip of foil between the foam and the casing, and then pull it out.
Inspired by Chris's example, I installed SDR Console.
I am learning how to use it and I see an advantage over HDSDR.
- installation is extremely simple and fast
- simpler operation, pleasant design
- richer menu
- probably lower noise level
- better operation of the AM Synchro mode
I am still checking the phenomenon of aliases, which in HDSDR irritate me a lot on HF. Perhaps Console's algorithms will be better than HDSDR in this physical phenomenon. The creator of the original BBRF103 receiver, Oscar Steila, developed and introduced filters: Notch FM Band, BPF FM Band and LPF 32MHz. You need to check this as well as the LO settings in relation to the band you are interested in.
4nradio:
Hi Chris, thanks for posting your RX-888 first impressions and the interesting screenshots.
My own RX-888 is showing fewer spurs and a lower noise floor when viewed in the same 32 MHz bandwidth with no attenuation in SDR-Console:
Here is the response with 20 dB attenuation:
I wonder what would account for this difference? Maybe I have some option or setting that varies from your own SDR-Console installation (I'm using 3.0.26, build 2017). I hope it's something like this, rather than quality control in the receiver.
The skeptic in me says "QA? whazzat??" when it comes to small-batch production runs from unknown electronics houses overseas, but I'm hoping it's just a software configuration matter ;D
73, Guy
Ray Lalleu:
--- Quote from: ChrisSmolinski on October 16, 2020, 2040 UTC ---The RX-888 is somewhat different than most direct sampling SDRs. Rather than having an onboard FPGA or other circuitry to decimate/reduce the bandwidth and produce an I/Q stream, it always streams raw 16 bit ADC samples over USB to the computer at the full 65 MHz rate. Your computer software is then responsible for performing these tasks, on top of the other signal processing to produce a waterfall, demodulated audio, etc.
This reduces the complexity of the SDR and presumably helps lower the cost. As computers are significantly more powerful than when SDRs first appeared on the market, this is probably a good trade-off.
--- End quote ---
Really ? With a tad of overhead, that makes a flow to the PC around 1300 Mbits/sec, so what is the line to the PC ?
And how can a PC process 65 Msamples/sec?
What is the equipment of your PC for the RX888 ?
ChrisSmolinski:
--- Quote from: Ray Lalleu on October 24, 2020, 1017 UTC ---
--- Quote from: ChrisSmolinski on October 16, 2020, 2040 UTC ---The RX-888 is somewhat different than most direct sampling SDRs. Rather than having an onboard FPGA or other circuitry to decimate/reduce the bandwidth and produce an I/Q stream, it always streams raw 16 bit ADC samples over USB to the computer at the full 65 MHz rate. Your computer software is then responsible for performing these tasks, on top of the other signal processing to produce a waterfall, demodulated audio, etc.
This reduces the complexity of the SDR and presumably helps lower the cost. As computers are significantly more powerful than when SDRs first appeared on the market, this is probably a good trade-off.
--- End quote ---
Really ? With a tad of overhead, that makes a flow to the PC around 1300 Mbits/sec, so what is the line to the PC ?
And how can a PC process 65 Msamples/sec?
What is the equipment of your PC for the RX888 ?
--- End quote ---
I'm running a 3.2 GHz i7-8700. It seems to handle the RX-888 fine, which only uses a small percentage of available resources and CPU time. SDR Console also makes use of GPU processing.
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