DWerk Posted August 13 Share Posted August 13 Has to make you wonder if the FMS is based on the harmonics themselves? Link to comment Share on other sites More sharing options...
Popular Post Chase Goldman Posted August 13 Popular Post Share Posted August 13 Mark's measurements show a two-frequency Simultaneous Multi-Frequency (SMF) transmit setup that is consistent with what most of the latest SMF detectors implement (e.g., Equinox) in that the SMF profiles utilize two or three frequencies in a fixed ratio for specific modes. In this case it is a roughly 3:1 rato. The "modes" in this case are the 3 FMF Max profiles: 14, 24, and 40 khz. Not to be confused with the base search "Programs" such as "General", "Fast", "Deep HC" etc. The Max FMF mode setting and ground handling/processing algorithms applied (i.e., frequency addition or conductive soil subtraction) define the optimal target objectives for each program by working in concert with the other key user adjustable parameters (e.g., sensitivity, disc/filters, reactivity, salt sensitivity, magnetic reject, etc., as applicable). A low FMF Max (14 khz) is used primarily for high conductor/large target "sensitivity" objectives at maximum detection depth (e.g., silvers and caches). High FMF Max (40 khz) is used for small target/low conductor sensitivity objectives (e.g., micro jewelry, natural gold). Because of the higher frequency, depth is limited but within the detection depth range of that 40 khz Max FMF, low conductive and micro targets will ring out better than if you were using 14 khz Max FMF. 24 khz is a great middle of the road FMF setting that gives you good sensitivity at depth for silver and good sensitivity for most smaller, low conductive targets - it's a great relic detecting range. Note that regardless of the FMF Max frequency chosen, the Max frequency changes consistent with the setting but the low to high frequency ratio remains fixed at around 3:1 regardless of whether 14 (4.4:13.5 khz) or 24 (7.5:22.8 khz) is chosen - I suspect that the base frequencies also shift slightly with a noise cancel while maintaining their 3:1 relationship. Harmonics happen as natural result of frequency mixing and the harmonics inherent in non-sinusoidal waveforms, but I believe the two discrete frequency waveforms are being transmitted separately and simultaneously despite being harmonics of one another and am not sure if the resulting non-transmitted harmonics play a role in target detection and signal processing. I could be wrong, though. I suspect that when Mark gets to his Mono and 40 khz FMF videos, we'll see 40 khz FMF utilizing the same 3:1 ratio. General, Sensitive, Sensitive FT, Fast, and Beach Sensitive -> Default FMF Max = 40 khz (Note: kind of surprised that XP chose 40khz as the default for General) (Fundamentals at TBD) Park, Relic, and Beach -> Default FMF Max = 24 khz (fundamentals at ~7.5 and 22.8 khz) Deep HC and Dive -> Default FMF Max = 14 khz (fundamentals at ~4.4 and 13.5 khz) But that's all somewhat beside the point, because what frequencies are actually being transmitted, while interesting from a curiosity perspective, don't really tell you much about the heart and soul of SMF detection, and that is the algorithms used to process the target signals that are induced by these transmit signals. XP is going to keep this proprietary signal processing secret sauce secret because how each manufacturer does this differs and that vs. what frequencies are transmitted is what really distinguishes the unique performance plusses and minuses between XP, Minelab, Nokta, Garrett and others who have jumped on the SMF bandwagon. We can only make guesses as to what happens under the hood. Doesn't really matter though, because results and ergonomics, not specs are what really matter in how we ultimately decide what detector best suits our personal detecting objectives. Looking forward to what Mark sees on his 40 khz FMF analysis and the default Mono frequency setpoints. 9 1 Link to comment Share on other sites More sharing options...
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