Time to try some more analog devices for noise reduction and antenna phasing, starting with the RA0SMS X-Phase QRM Eliminator kit.
In the past, I have written extensively about shortwave noise cancellation using my ANC-4. These devices are great for eliminating RFI from consumer devices in your neighborhood. ANC-4 is an analog phase shifter for cancelling a nearby noise source. Similarly, I can do this digitally with my coherent dual channel receivers like the RSPduo.
Many hams have also used cheaper devices generically called “X-Phase QRM Eliminator”. I thought I should give one of these a try. These devices have similar circuits and use variable resistors for gain balancing and phasing. For starters, I chose the RA0SMS X-Phase kit from Anton in Irkutsk, Russia. It gets good reviews.
You can buy one of these for $21 on eBay. Mine arrived this week in a padded envelope containing a double sided printed circuit board, a package of parts and a schematic, as shown above. Shipping took about 7 weeks.
Although there are not really any assembly instructions, Anton shows pictures of built units on his web site. I think all the parts are here. However, the SMD components are not clearly marked and will require some checking. Most of the parts are through hole and I should not have much difficulty with assembly. Fingers crossed.
RA0SMS X-Phase QRM Eliminator in LTSpice
Last year, I built a simulation model of the RA0SMS X-Phase in LTSpice. Performance looked pretty good with potential phase null of interference in the 35-40 dB range. Also, while this model is specified to work in 1.8 to 30 MHz range, the Spice simulation indicates that it should also work down into medium wave, as well.
In addition to noise reduction, I intend to experiment with using my X-Phase to phase two wideband loop antennas. My intention is to create some diversity reception techniques with single channel receivers like my Perseus and Flex 6300. Again, fingers crossed.
I will report back after I put the unit together next month.