Knowing the release of the new Diversity software for the RSPduo was imminent, I tried my best to be ready for the happening.
SDRuno Ver. 1.32 provides the facility of Diversity by operating the two Tuners of the RSPduo simoultaneously on the two coaxial 50 Ohm inputs. Of course one at the beginning is very curious to compare Diversity/non Diversity operation at the same time and on the same signal. This can be done with the setup described here.
Having a 160 m Beverage already, I set up a 60 m long wire, as shown in Figure 1. Both antennas exploit the same return lead, or counterweight. I tried to place the antenna ends as far as possible from each other, also making sure they would be at 90° approximately, in order to try and have the widest possible phase & directivity differences in operation.
Both wire antennas come into the radio room and their leads are arranged as shown in Figure 2. The 60 m long wire 600 Ohm (nominal) impedance level is scaled down to 50 Ohm by a wideband ferrite transformer, ready for use. The 160 m Beverage, 450 Ohm impedance level, is scaled down to 50 Ohm by a second ferrite wideband transformer and brought to a 3 dB Hybrid splitter, whose two outputs are ready for use.
The rationale is to use one of the two leads of the Beverage to feed the comparison RSP-1A receiver. The other lead of the Beverage feeds Tuner 1 of the RSPduo. Tuner 2 of the RSPduo is fed by the 50 Ohm output of the 60 m long wire. This complete setup is shown in Figure 3.
As was to be expected SDRuno v. 1.32, in Diversity mode requires significantly higher PC capacity, because two Tuners have to be operated simultaneously. For this reason the RSPduo is operated by a LENOVO T540p, Windows 10 laptop, (Processor I5 5th generation / 8 GB RAM) with practically no other software loaded in. The RSP-1A is easily handled by the old stand-by, the LENOVO X61.
More in the next post.
- FIGURE 1. ANTENNAS READY FOR TESTING
- 1. Diversity antennas.jpg (368.7 KiB) Viewed 2908 times
- FIGURE 2. TEST CIRCUIT MECHANICS
- 2. Diversity test circuit 1.jpg (57.27 KiB) Viewed 2908 times
- FIGURE 3. COMPLETE TEST CIRCUIT
- 3. Diversity test circuit 2.jpg (60.48 KiB) Viewed 2908 times
Reason: No reason
Figure 4 shows RSPduo Diversity on left laptop and control RSP-1A in operation on right laptop. Figure 5 shows the antenna interconnections. To minimize PC generated interference, the RSP's are remoted. Finally Figure 6 shows a -117 dBm signal (invisible on the display) comfortably copied on the duo, but competely lost in noise on the 1A: this is an extreme situation.
Diversity action is clearly visible when the 60 m long wire has enough signal to give a contribution, then Diversity S/N advantage over control S/N can reach a very significant value, allowing copy of signals normally buried in the noise. On those istances when signal is far stronger on the 80 m long wire, then, of course there is no comparison: noise from the control and solid copy on the duo. But I shall describe operation in detail in a next post.
- FIGURE 4. Diversity system & control in operation
- 4. RSPduo-RSP-1a compare .JPG (122.71 KiB) Viewed 2845 times
- FIGURE 5. Antenna connections with matching transformers & 3 dB Hybrid
- 5. Diversity connections.JPG (190.29 KiB) Viewed 2845 times
- FIGURE 6. EXTREME COPY SITUATION
- 6. Reception @ -117 dBm.png (474.79 KiB) Viewed 2845 times
Reason: No reason