It’s early days yet, for the new SDRuno diversity software which we recently launched with V1.32 for use with the dual tuner SDRplay RSPduo.
We are working on some video guides and more information on how it works. (new video added – July 22nd 2019: https://youtu.be/x1DRgprcC6g )
Meanwhile I’d like to point out that there are 2 very practical applications for this software. The first is MRC (Maximum Ratio Combination) Diversity which, in order to be effective, needs two antennas presenting the same signal with some degree of diversity. Examples of diversity are:
Spatial Diversity: Using two antennas that are physically separated from one another. Depending upon the expected incidence of the incoming signal, sometimes a space on the order of a wavelength is sufficient. Other times much larger distances are needed – this can be challenging for HF frequencies and below.
Pattern Diversity: Using co-located antennas with different radiation patterns. This type of diversity makes use of directional antennas that are usually physically separated by some (often short) distance. Collectively they are capable of discriminating a large portion of angle space and can provide a higher gain versus a single omnidirectional radiator.
Polarization Diversity: Combining a pair of antennas with orthogonal polarisations. Reflected signals can undergo polarization changes depending on the medium through which they are traveling. A polarization difference of 90° will result in an attenuation factor of up to 34 dB in signal strength. By pairing two complementary polarizations, this scheme can immunize a system from polarization mismatches that would otherwise cause signal fade.
The key thing it to experiment and once you provide some degree of diversity as described above. The “APPLY AUTO” button in SDRuno will select the optimum combination of amplitude and phase to give you an enhanced signal versus either one of the individual signals.
The second application is for local noise cancellation. Here you are using manual control of the phase and amplitude to subtract the unwanted interference from the wanted signal. There is already one very good YouTube demo out there which was made by ICAS Enterprises, one of our Japanese resellers:
The author writes as follows:
This is an experiment showing how to cancel local noise appearing around the FT8 freq on 20m band with a combination of SDRuno V1.32 and RSPduo.
Background: Weak signals (and even stronger ones) are buried under the local noise at FT8 freq on 20m band.
Solution: With the use of the SDRuno V1.32 and RSPduo, the noise can be theoretically canceled.
Rig Setup: An LZ1AQ active loop is connected to Tuner 1 of RSPduo, and a 4.7VDC operatable active whip connected to Tuner 2 respectively. LA1AQ: 15m abg, Active Whip: 17m abg – Two antennas placed about 5m apart.
What you can see in this video:
0″-10″: You can observe strong noise both on Tuner 1 and Tuner 2 (SINGLE mode).
11″- : Switched to DIVERSITY mode.
20″-35″: The active whip connected to Tuner 2 is run by T-Bias 4.7VDC supplied from RSPduo, but when the mode is switched from SINGLE to DIVERSITY, the basic settings will be reset, so there will be no 4.7VDC supplied even if the BIAS-T button is inverted after the mode change. During this period, the spectrum shown is from Tuner 1 only. So, there will be no change in the noise level even if the “APPLY AUTO” is pressed or the ampl/phase manually adjusted. Anyway, you see the big noise is there!
36″- end: Toggling twice the BIAS-T button, you can get the Tuner2 antenna working. When manually adjusting the ampl/phase to the point where the noise becomes minimum, you can see some signals are floating up with much higher readability. When applying “APPLY AUTO”, the noise becomes maximum where weak signals are barely readable. Note: You don’t have to worry about the “BIAS-T” issue when you use any antenna that is NOT of active type. The reason why I am using an active whip is such that it can easily pick up local noises. Also, it is quite easy to set up such a small antenna almost anyplace.
————– end of quotes from the video———————
Please note the Bias-T reset when using diversity is a quirk of the current software release and will be fixed in a future release
We would welcome more practical videos about diversity reception, made by users – we’d love to showcase the best ones on our YouTube channel and add links to them from our applications and support catalogue: https://www.sdrplay.com/apps-catalogue/
You can email links to me at email@example.com
SDRuno manual (see Page 78): https://www.sdrplay.com/docs/SDRplay_SDRuno_User_Manual.pdf
July 18th update:
ICAS Enterprises have just released a follow-up video which futher explains what’s going on with the RSPduo noise cancelling demonstrated above:
This is the text which accompanies the second video:
How RSPduo/SDRuno V1.32 cancels out noise under a quasi environment-
When it comes to noise canceling, the same theory applies to both software and hardware noise canceling equipment. This time we have carried out an noise canceling experiment under a quasi environment for your easier understanding purposes.
Equipment used: RSPduo + SDRuno V1.32 NG (wide band noise generator) SG (signal generator – 14MHz)
Settings: NG’s output was equally distributed to Tuners 1 and 2. SG’s out put was loosely coupled to both Tuners 1 and 2, but Tuner 2 being less strongly coupled.
Explanations per time lapse:
0″-15″: Showing how each equipment is set out.
15″-22″: Showing SDRuno spectrum (Tuner 1) with both NG and SG tuned OFF.
22″-26″: Tuned NG ON, showing Tuner 1 spectrum.
26″-30″: NG being ON, switched to Tuner 2 spectrum.
30″-33″: Turned NG OFF. .
33″-37″: Turned SG ON, showing Tuner 1 spectrum.
37″-43″: SG being ON, switched to Tuner 2 spectrum.
44″-50″: SG being ON, switched back to Tuner 1 spectrum.
49″-55″: SG being ON, turned NG ON. The target 14MHz signal is barely readable.
55″-1’01”: Both SG/NG being ON, switched to Tuner 2 spectrum. The target 14MHz sig is NOT readable at all.
1’01”-1’15”: Switched to DIVERSITY mode. Tuner on APPLY AUTO, maximizing the noise.
1’15”-1’31”: Turned APPLY AUTO OFF, manually maximize S/N for the target sig. The burried sig can be now readable!
1’31”-1’39”: Again, Tuner APPLY AUTO ON to maximize the noise.
1’39”-1’47”: Turned APPLY AUTO OFF, and manually maximize for the best S/N.
1’47”-1’49”: Turned SG OFF, the target sig gone, but the noise floor level kept unchanged.
1’49”-2’12”: Cycling NG ON/FF. Both ends of the spectrum slightly went up and down.
2’12”-end： Repeated tuning APPLY AUTO ON and OFF.
Key to successful noise cancelation: Usually, the main antenna is connected to Tuner 1. It is advisable to connect to Tuner 2, such an antenna that can receive the noise at the same or slightly higher level as the antenna of Tuner 1, while the target signal should be weaker with Tuner 2 ant than with Tuner 1 ant. We have reproduced such an environment by making the SG output coupling to Tuner 2 weaker. We hear a lot of times “I cannot cancel noises using a hardware noise canceler (of a well-known make).”Most of the cases, the noise level introduced into the canceler is too weak, so it will not effectively cancel out the noise in question received on the main antenna. Should the noise strength received on your noise pickup antenna be a little too strong, you can reduice the level with the RF GAIN of T2 on the MAIN window of the SDRuno.
Here’s a new SDRplay video added on July 22nd: