I have one of these. They are excellent for what they can do vs other sdrs. Ie not a complete replacement for everything else. But a tool to be used along side them. Seeing the whole hf spectrum at once or monitoring all the ham bands at once is amazing. I have ethernet over power in my house and its instantly visable. To see the same on a tinysa you have to put it into max hold mode and wait 10 minutes. Where as the rx888 mk2 shows the entire instantaneous spectrum. Yes a lpf is a good idea.. but i only have ham band resonant antennas and there usnt much local transmissions 32Mhz to at least 70ish Mhz. Ive not seen any alias of the local FM radio broadcast stations. Like others have said there is no 32mhz lpf. Only a 64mhz one which isn't the greatest. All the considered im very happy with it. I was very interested in ionosondes transmitters at the time i bought it and of course it works really well for tracking them across the whole hf spectrum. Some i believe are military. Regards VK6MIK
Thank you for benchmarking the RX-888 MKII using high end equipment. That is a wonderful contribution to the SDR community. I have numerous SDR’s. Bought an RX-888 MKII for its 32Mhz receive bandwidth. Comparing it to the HF+ Discovery is not really applicable. These are two different expressions of “SDR”, for different applications. Example, please show us 30Mhz bandwidth receive result from HF+ Discovery. Oh, it can’t do that? Why is that pray tell? Because it was designed to be narrow band with front end filters? Hummmm.
I just tested the RX-888 today and I am extremely pleased so far. It is a 128MHz max sampling ADC and the LPF is then designed for 64MHz, isn’t it? Twice the HF band and thus an issue for anybody expecting it to adjust its filter if you sample at 64MHz. Or am I seeing this wrongly? I purchased a broadcast FM (and AM) notch filter for this reason (will be using it at 75MHz).
4:46 Slight adjustment to equation: Radio noise floor = Pn = k * T * B, where Pn = power of thermal noise generated by the receiver in watts, k = Stefan-Boltzmann constant (1.38 x 10^{-23} J/K), T = temperature in kelvins, and B = bandwidth in hertz. For frequencies less than ~100 MHz, atmospheric noise coming into the receiver's antenna usually dominates thermal noise. (See RGSB pamphlet online titled "The Background Noise on the HF Amateur Bands.") The RX-888 MKII "V" antenna input covers 64-1700 MHz, where the receiver noise floor does matter. 5:28 A bullet point says "Poor 32 MHz LPF in the front end," however the RX-888 MKII description at AliExpress says it has an improved 64 MHz LPF, so it won't do much to attenuate a 65 MHz frequency. Here is an example of an RX-888 MKII receiving the entire 0-64MHz range: ua-cam.com/video/lDxWIStUC0Q/v-deo.html
Yes thanks for noise equations typo, as for noise floor, I just measuring it, as for 64 mhz lpf, I did 88.1mhz in and still saw the alias signal, so internal lpf is junk, so I still stand by the statement that an external lpf will be needed, and other swl articles have made the same point. My results are from test, not from a cranky ham typing on UA-cam. 73s. 😂😂😊😊
Why not some video showing your testing environment and procedures? Yes, the SWW200A is good but so is a Keysight M9383B and others. Does it matter if you're just testing a $300 SDR? Testing this SDR is easy but I'm concerned about how you performed your tests. Why? Because you come across as a competitor and not a unbiased reviewer. Those birdies that you show may be from your PC USB 3 port. Did you try a ferrite core to reduce RFI on the USB cable?
I showed the results, what more do you want? Biased? I am just showing how the signals aliased down. I guess taking measurements is Biased, I think you want to go to techminds channel, he isn't Biased, and doesn't do any measurements 😅😅😅😊😊
Thanks for your detailed test. I have already purchased this SDR. Can you be more specific on the value of the LPF that you suggest? Maybe you can point me to a book or web page that explains. All of this is very interesting!
Depends on the sample rate. His software seems to operate the unit at only half its rated sample rate, so you can't really blame the fixed internal LPF for not getting rid of lowband VHF. Whatever filter is used should start to roll off below half the sample rate and reach its stoppband attenuation just above it. The important thing is that it has sufficient attenuation to get rid of any strong local signals above half the sample rate. Depending on the sample rate, these probably include lowband VHF land mobile, lowband VHF TV and FM broadcast. I am writing my own software from scratch (on Linux) and don't run Windows at all, so I'm unfamiliar with the software he's using. It wouldn't surprise me that it simply cannot handle the full rated sample rate of the unit, but this is the fault of the software, not the unit. This is true even if you're only interested in HF (0-30 MHz) because aliasing will still occur on signals above half the sample rate. One solution may be to operate the hardware at its full sample rate (about 128 MHz) and then use a fast simple digital low pass filter to remove everything between 30 and 64 MHz. The higher sample will completely stop lowband VHF aliasing, and the low pass filter will allow the sample rate to be halved for the rest of the SDR that can't handle the full 128 MHz rate. But the unit will still need a hardware lowpass filter to remove anything above 64 MHz that still gets through the internal LPF. A FM broadcast band notch filter would be a good start.
Great channel. Lots of useful bits. Subscribed. Cheers ...
I have one of these. They are excellent for what they can do vs other sdrs.
Ie not a complete replacement for everything else. But a tool to be used along side them. Seeing the whole hf spectrum at once or monitoring all the ham bands at once is amazing. I have ethernet over power in my house and its instantly visable. To see the same on a tinysa you have to put it into max hold mode and wait 10 minutes. Where as the rx888 mk2 shows the entire instantaneous spectrum. Yes a lpf is a good idea.. but i only have ham band resonant antennas and there usnt much local transmissions 32Mhz to at least 70ish Mhz. Ive not seen any alias of the local FM radio broadcast stations. Like others have said there is no 32mhz lpf. Only a 64mhz one which isn't the greatest. All the considered im very happy with it. I was very interested in ionosondes transmitters at the time i bought it and of course it works really well for tracking them across the whole hf spectrum. Some i believe are military. Regards VK6MIK
Thank you for benchmarking the RX-888 MKII using high end equipment. That is a wonderful contribution to the SDR community.
I have numerous SDR’s. Bought an RX-888 MKII for its 32Mhz receive bandwidth. Comparing it to the HF+ Discovery is not really applicable. These are two different expressions of “SDR”, for different applications. Example, please show us 30Mhz bandwidth receive result from HF+ Discovery. Oh, it can’t do that? Why is that pray tell? Because it was designed to be narrow band with front end filters? Hummmm.
I just tested the RX-888 today and I am extremely pleased so far. It is a 128MHz max sampling ADC and the LPF is then designed for 64MHz, isn’t it? Twice the HF band and thus an issue for anybody expecting it to adjust its filter if you sample at 64MHz. Or am I seeing this wrongly?
I purchased a broadcast FM (and AM) notch filter for this reason (will be using it at 75MHz).
4:46 Slight adjustment to equation: Radio noise floor = Pn = k * T * B, where Pn = power of thermal noise generated by the receiver in watts, k = Stefan-Boltzmann constant (1.38 x 10^{-23} J/K), T = temperature in kelvins, and B = bandwidth in hertz. For frequencies less than ~100 MHz, atmospheric noise coming into the receiver's antenna usually dominates thermal noise. (See RGSB pamphlet online titled "The Background Noise on the HF Amateur Bands.") The RX-888 MKII "V" antenna input covers 64-1700 MHz, where the receiver noise floor does matter.
5:28 A bullet point says "Poor 32 MHz LPF in the front end," however the RX-888 MKII description at AliExpress says it has an improved 64 MHz LPF, so it won't do much to attenuate a 65 MHz frequency. Here is an example of an RX-888 MKII receiving the entire 0-64MHz range: ua-cam.com/video/lDxWIStUC0Q/v-deo.html
I was going to make the exact points. Thanks.
Yes thanks for noise equations typo, as for noise floor, I just measuring it, as for 64 mhz lpf, I did 88.1mhz in and still saw the alias signal, so internal lpf is junk, so I still stand by the statement that an external lpf will be needed, and other swl articles have made the same point. My results are from test, not from a cranky ham typing on UA-cam. 73s. 😂😂😊😊
What difference does it make to have sensitivity down to -145 dBm, when HF is any way full of noise?
Can use it for downconverter for other bands
Why not some video showing your testing environment and procedures? Yes, the SWW200A is good but so is a Keysight M9383B and others. Does it matter if you're just testing a $300 SDR? Testing this SDR is easy but I'm concerned about how you performed your tests. Why? Because you come across as a competitor and not a unbiased reviewer. Those birdies that you show may be from your PC USB 3 port. Did you try a ferrite core to reduce RFI on the USB cable?
Good point, the birdies, I had ferrite core. It's a good rx888, only real issue is it needs a low pass filter for alias protection.
I showed the results, what more do you want? Biased? I am just showing how the signals aliased down. I guess taking measurements is Biased, I think you want to go to techminds channel, he isn't Biased, and doesn't do any measurements 😅😅😅😊😊
Thanks for your detailed test. I have already purchased this SDR. Can you be more specific on the value of the LPF that you suggest? Maybe you can point me to a book or web page that explains. All of this is very interesting!
The lpf should be 30mhz lpf, if the highest frequency of interest is 10mhz, a 20mhz lpf good
Depends on the sample rate. His software seems to operate the unit at only half its rated sample rate, so you can't really blame the fixed internal LPF for not getting rid of lowband VHF. Whatever filter is used should start to roll off below half the sample rate and reach its stoppband attenuation just above it. The important thing is that it has sufficient attenuation to get rid of any strong local signals above half the sample rate. Depending on the sample rate, these probably include lowband VHF land mobile, lowband VHF TV and FM broadcast.
I am writing my own software from scratch (on Linux) and don't run Windows at all, so I'm unfamiliar with the software he's using. It wouldn't surprise me that it simply cannot handle the full rated sample rate of the unit, but this is the fault of the software, not the unit. This is true even if you're only interested in HF (0-30 MHz) because aliasing will still occur on signals above half the sample rate. One solution may be to operate the hardware at its full sample rate (about 128 MHz) and then use a fast simple digital low pass filter to remove everything between 30 and 64 MHz. The higher sample will completely stop lowband VHF aliasing, and the low pass filter will allow the sample rate to be halved for the rest of the SDR that can't handle the full 128 MHz rate. But the unit will still need a hardware lowpass filter to remove anything above 64 MHz that still gets through the internal LPF. A FM broadcast band notch filter would be a good start.
The Techminds guy .. always rude to commenters.