I found an interesting article by Bob N6TV where he specifies a band scope built from an SDR using the FT1000MP RX in/out ports. I ordered an RTL-SDR dongle and a 3dB splitter from eBay to test it. I have the following setup below with HDSDR installed with pretty easy configuration.
The first tests are really interesting.
- definitely you need well matched antennas. At the first try I blacked out the SDR with the 40m dipole as it has relatively narrow bandwidth and surely current on the coax shield as well.
- I have thought beforehand that the 3dB will be really missing from the reception. Actually the QSOs made had no really visible S-meter/signal strength degradation if I used the “full antenna” power to the TRX receiver or splitted between the TRX and the SDR.
- I have gaps in the handling of the HDSDR but the biggest challenge at the moment is to set the correct spectrum zoom, scaling and minimum level settings which are band dependent. This might be due to the small antennas I have @play station but needs to be figured out how can I set them once.
- there is (not surprisingly) a ~400ms latency between the TRX and the SDR processed sounds. It is not disturbing tho.
- Sometimes I even feel that the SDR has better ears compared to FT1000MP. SDR definitely has advantage on noise immunity. It even feels like more comfortable noise floor however I love my MKV Field. The HDSDR notches are simply great. Would be great to have special HW to control this like FlexRadios do.
- being very visual this is excellent view on the band. This can be a good addition in the contests even if I’m in assisted category.
However I still cannot imagine how useful tool I might have with this band scope but I will try to
- connect the whole stuff to a skimmer server just to see how it works.
- try the SN2M style stereo reception on low bands.
I would like to say a big thanks to Bob N6TV for his hints and support actually not only in this SDR topic.