I would appreciate some thoughts on a conundrum.

[JohnA]

There are stretches of a beach I hunt where my X-70 with the 3kHz and 5X10 coils and my Quattro with any coil have either buried cable interference or interference from nearby condos and hotels. No combination of the usual setting tweaks eliminate the interference. My 7.5kHz concentric and Excal 1000 have no issues with the interference and run smoothly. The Excal has shielding and/or circuitry to combat interference and the 7.5kHz/concentric coil combo is a sweet spot? I was considering buying the 18.75 kHz round DD, however wondering if I should buy the 7.5kHz round DD coil, or is the DD design a deal breaker? Sure enough, I found older targets in the noisy stretch with the 7.5 kHz coil I and other detectorists have missed. Nothing great, but you never know. I want a little more coverage. Thanks in advance.

 

[BarnacleBill]

This is a tough one for sure. I have just had the 10.5 7.5 KHz DD for about 10 days and it appears to me to be about 10% more sensitive than the other coils. It is also more sensitive to a buried electrical cable in a gravel road I detect around. There may also be data lines in the trench, but most likely twisted pair, so emissions may be low. So far the X-Terras have been the quietest detectors around these lines compared to the other brands I have. As the 7.5 KHz has been the quietest then that may be the route to go.

But I assume you have no way of knowing the source, 60Hz electrical, radio, etc. One thing you might try is a standard transistor radio on the AM band. Find a clear part of the band without stations, at a place on the beach as far as you can get from the interference area. Then with the volume cranked up walk towards the area of interest to see if you pick up noise. If you do, turn down the volume so that you can notice changes in signal level. The AM antennas in transistor radios are ferrite bar antennas which are directional, so turning it in your hand can give a bearing.

If it turns out to be an undersea cable feeding an island there's not much you can do. But it it's an outdoor lamp, neon sign etc and it's interfering with your radio, then you can make a request it be fixed. In the USA radio interference is a no-no, however it might take some effort to get the FCC to do something about it.

HH
BarnacleBill

 

[JohnA]

Thanks. The radio trick sounds interesting. I will try it soon and if I figure out something worthwhile reporting, I will do so.

 

[Reconmarine1984]

I agree, I returned to many of my relic sites that where " Uncountable" due to Power lines, Micro Towers, and ungrounded power lines etc.. I can run my X-70 Sen. high with 10.5DD 7.5 in this higher interference area around 25/26 most time. I made lots great finds , and most other brand of machines that are unless its MInlab with Noise Cancel Ect. Another Reason to have an X-70!!!

 

[JohnA]

I was thinking it was more a frequency related interaction rather than the type of coil, as the 3 kHz coil which is concentric is also noisy. Will try some of the tricks Barnacle Bill suggested, but it appears I may be getting the 7.5 kHz DD coil. As an aside, I continue to be amazed with the 6" DD coil. It doesn't come off when I hunt inland.