An interesting observation on frequency

[PryorCreekJoe]

I was relic detecting on Sunday and running a modified Gmaxx mode (in 8kHz). I was in an area where there were what looked like pieces of granite rock. When I ran the coil over the rocks it sounded off like like a hot rocks. When I changed to 12 kHz, not a peep. Any good explanations on this? I can see this as possibly a good thing to remember while hunting in hot rocks but don't know if would be repeatable on other kind of hot rocks. I wish now that I had picked up one of the rocks to take home and study this a bit more but I didn't. Anyway, it was an eye opener for me as to the difference changing frequency can make.

 

[Big Boys Hobbies]

Great info Joe! Thanks!

 

[samandnoah]

Not exactly the same, but had my own experience with 2 similar programs using different frequencies. On some targets, the higher frequency would show a potentially good target (say, in the 60s), and the lower frequency would show it at 6, and sound off as iron. And then other targets, it seemed to reverse. I'm trying to reproduce those results and record them. Could have been bad GB on my part. And the programs are not identical, and am trying to bridge the various setting differences to see if one of those adjustments created that experience. But the most obvious difference was frequency, and my first assumption was that was the cause of the difference. Will be very interested in seeing more responses to your experience.
Regards,
Rich

 

[Topdecker]

I had a similar experience, but had an advantage in the sense that I knew the terrain pretty well. I was hunting along the borders of an old sidewalk that had given me a lot of trouble in previous visits. Basically, the old sidewalk had been covered with coal ash / grit during the winter months and this had been done for years and years. The sidewalks have a 2 to 4 foot zone around them that is basically filled with little gritty pieces of coke.

Anyhow, the 8khz mode was very noisy and it calmed right on down at 12khz. I punched it up to 17khz, but then aluminum bits started falsing and 12khz seemed like the best trade-off. In fact, I haven't switched out of 12khz once I encountered this.

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[pulltabMiner]

Interesting observation. I will keep it in mind.