So, what’s the verdict on X-Phase performance for reducing RFI during shortwave listening? Pretty good, actually, for something so cheap and cheerful.
Total cost of my X-Phase QRM Eliminator comes to around $30. This includes the RA0SMS kit, shielded plastic box, switches and connectors. I spent about a day putting it all together. Let’s compare this to an ANC-4, which comes in at around $200, or MFJ-1026 at $240.
My main use case is reducing RFI from noisy neighbors, 100 to 500 feet distant. My main offender is poorly wired halogen lights in one nearby kitchen. Other sources include router birdies, VDSL emissions and many crappy switch-mode power supplies that permeate my environment. My antenna setup includes either noise probes with my main antenna or a pair of wideband active loops 100 feet apart.
My verdict on X-Phase performance is 70 to 80% compared to the ANC-4 at 15% the cost. It does really well on eliminating the halogen lights RFI, pretty well on the router birdies and mixed on the SMPS emissions in the HF range.
So, if you want to give the RA0SMS X-Phase a try, you should not be disappointed on a price-performance basis.
You will find various assembled units online at prices ranging from $70 to $120. (All amounts U.S. dollars.) My advice would be if you are going to spend more than $100 for an assembled X-Phase, consider just going for the ANC-4 if you can find one.
X-Phase Performance Nitty Gritty
As with most devices of this type, there is quite a bit of interaction between the three controls, particularly the AUX antenna gain and the Phase control. Generally I set the Main antenna gain first, then adjust the AUX and Phase to get a QRM null. Also, I find that the Phase control tends to function mostly near the CCW position regardless of how the Gain controls are set.
Switched off, insertion loss is about the same as the ANC-4 at 6 dB or so. Switched on and adjusted, RFI reduction can easily exceed 20 dB.
When using the X-Phase with a wideband loop, it’s easy to get intermodulation products from local AM broadcast stations if you set the Main Gain too high. You can eliminate this problem with an AM bandstop filter inserted ahead of the QRM eliminator.
You can easily test X-Phase performance by feeding a signal generator into both the Main and AUX inputs, and watching OUT performance on a scope. On my unit, I find performance under 3 MHz drops off quickly.