HFU HF Underground
Technical Topics => SDR - Software Defined Radio => Topic started by: ChrisSmolinski on August 21, 2019, 1949 UTC
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Another SDR DGPS shootout, this time the SDRplay RSPduo vs AirSpyHF+ Discovery. Again, the 950 ft Log antenna through a low pass filter and splitter, so each SDR was running at the same time. I ran two instances of SDR# to keep things as fair as possible. The test was run mid afternoon, so not much DX expected. I used the Hi-Z port on the RSPduo, fed with one of my Cyclops transformers in reverse, which seems to produce higher signal levels vs the COAX input.
The DGPS band is 285-325 kHz, so these results may be applicable to NDB enthusiasts as well.
The 950 ft LoG (Loop on Ground) antenna is fed via one of my Cyclops antenna transformers and then coax to the shack
https://www.blackcatsystems.com/rf-products/cyclops_rf_ham_shortwave_radio_matching_transformer.html
All decoding done with Amalgamated DGPS of course, the premier DGPS decoding software. https://www.blackcatsystems.com/software/dgps_decoding_software_sdr.html
I think it was pretty much a tie?
RSPduo:
Count ID ref1 ref2 kHz Baud City Country Lat Lon km Deg
100 799 044 045 290.0 200 Penobscot, ME United States 44.453 -68.776 858 49
949 778 192 193 292.0 100 Kensington, SC United States 33.491 -79.349 723 198
207 929 312 313 296.0 200 St Jean Richelieu, QC Canada 45.324 -73.317 693 24
70 838 116 117 319.0 200 Detroit, MI United States 42.306 -83.103 590 301
4178 772 198 199 306.0 200 Acushnet, MA United States 41.749 -70.889 561 64
3896 844 094 095 324.0 200 Hudson Falls, NY United States 43.272 -73.542 489 35
1682 839 118 119 322.0 100 Youngstown, NY United States 43.239 -78.972 427 338
3078 803 006 007 293.0 100 Moriches, NY United States 40.794 -72.756 378 70
2816 806 012 013 289.0 100 Driver, VA United States 36.963 -76.562 307 173
4824 804 008 009 286.0 200 Sandy Hook, NJ United States 40.475 -74.02 266 70
Discovery:
Count ID ref1 ref2 kHz Baud City Country Lat Lon km Deg
109 799 044 045 290.0 200 Penobscot, ME United States 44.453 -68.776 858 49
1000 778 192 193 292.0 100 Kensington, SC United States 33.491 -79.349 723 198
208 929 312 313 296.0 200 St Jean Richelieu, QC Canada 45.324 -73.317 693 24
65 838 116 117 319.0 200 Detroit, MI United States 42.306 -83.103 590 301
4263 772 198 199 306.0 200 Acushnet, MA United States 41.749 -70.889 561 64
4027 844 094 095 324.0 200 Hudson Falls, NY United States 43.272 -73.542 489 35
1692 839 118 119 322.0 100 Youngstown, NY United States 43.239 -78.972 427 338
3076 803 006 007 293.0 100 Moriches, NY United States 40.794 -72.756 378 70
2829 806 012 013 289.0 100 Driver, VA United States 36.963 -76.562 307 173
4829 804 008 009 286.0 200 Sandy Hook, NJ United States 40.475 -74.02 266 70
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Did you have the rsp set to use decimation that would cover the same spectrum as the discovery? Also what IF mode was employed with the rsp?
"premier DGPS decoding software"
:D
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Did you have the rsp set to use decimation that would cover the same spectrum as the discovery? Also what IF mode was employed with the rsp?
Yes, I used the low IF mode along with appropriate decimation to keep the sample rates as close to the same as possible between SDRs.
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Have you run a test on HF? Say, record the pirate band with both?
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I may have done some comparisons a while back (maybe even some audio recordings or a video?). I find them tricky, since unlike the DGPS decoding the results are somewhat arbitrary. It rarely is a case of "I can hear the station on SDR A but not B" but instead "I think it sorta sounds better on A but not really sure oh now it sounds better on B".
My general experiences are:
The netSDR is a tank. It does not overload. It's a direct sampling 16 bit SDR with bandpass filters. You do not see images. If the signal is there it is real. If it can be picked up, you will pick it up. It is what I use for my nightly 43m recordings that hear everything. It works. If you ever see one of these for sale cheap, buy it. You will not be disappointed.
The SDR-14 is kinda old now, it's OK, I would not buy one unless you get an awesome deal.
The SDRplay and AirspyHF+ models all have their pluses and minuses. They're a good deal for the money, about an order of magnitude less than the netSDR. The netSDR is not 10x better, but it is somewhat "better" in that you won't get fooled by overloading or other effects causing images. Also as these receivers all use a form of AGC the signals sometimes bounce up and down which is annoying when you are used to it not happening. You can mitigate it with careful adjustment of settings. But you do need to be aware of the fact that you can sometimes fool yourself. Any of these is your entry point for a low cost SDR.
The AFE822x is IMHO an under-appreciated SDR. You get a lot for the money. It's got two inputs and you can do phasing with it with SdrDx. It's direct sampling, so no wonky AGC action. It has a built in adjustable LNA, which I like because I can use it with my passive crossed parallel loop or another antenna with a lowish signal level and max out the A/D bits. Only 12 bits, but it seems to be enough. It is my main receiver for 48 meter Europirates, and does well on MW also.
The less said about the RTL Dongle the better. Again in fairness on VHF/UHF it is great for the price, and works pretty well. But not on HF. It's garbage on HF, I will be that blunt. I've noticed then when I run into someone online badmouthing SDRs in general, it's because their only experience is with an RTL Dongle.
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Thanks for the reply. I'm sort of interested in what SDRplay will have coming out (I feel pretty certain that they're going to unveil a new unit in time for the holidaze) but in my high RF environment it might be worth my while to just save up and get something in the NetSDR/Perseus class.