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   Aluminum makes a great heat sink! If you have ever disassembled a computer, you will notice the large finned block of aluminum in direct contact with the CPU! 

   Foil on the outside of the pod won't do much to dissipate heat, but if it blocks EMI, and reflects heat externally( sun from the black housing)! Than its worth the application! You can leave the speaker area open for heat dissipation, if your worried! 👍👍

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So I thought nothing ventured nothing gained. I have about three blocks of beach where the EMI forces me to turn the sensitivity down to 20. Also sick of hearing all the cell phones coming at me from

I had become so accustomed to wired headphones that it really is no big deal to me! What i did change on a few of my detectors is running an extension  to the rear, under the arm cuff! I hate my headp

This time of year you could use the foil, but when summer comes along you better let the unit get rid of the heat.

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2 hours ago, dewcon4414 said:

So is it the boards arent grounded?   I wouldnt think the box would pick up much EMI.  Most of the EMI should be comes from the coil.

Sure, the coil can be a source, but unshielded electronics can act like a receiver to pick up external signals if they are strong enough.  The “cell phone too close to the control pad” causing noise is a prime example of this.  Electronic junctions (a diode, for example) can act like the old crystal set radios did to detect signals.

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10 hours ago, dewcon4414 said:

So is it the boards arent grounded?   I wouldnt think the box would pick up much EMI.  Most of the EMI should be comes from the coil.

Well in 8 hours of use I lost all of my EMI on this beach with the foil in place. Working on a more permanent fix. 

I am 100% sure this EMI is from communications equipment. Would like to hear from someone who try's this on overhead power lines

Dave

 

 

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My test location was going to be near a radio tower, that's bristling with directional microwave antennae, probably 5 GHz and up, but may well have lower freq cellphone gear on it, 800 MHz & up. It drives my Fisher F75 mad, I found that positioning myself so my body was between the tower and the control-box, made a significant improvement. The sight of me walking backwards across the field would no doubt have left observant onlookers puzzled. But they would probably assume I'm wierd simply for metal detecting ... so it may just be dismissed as 'fruitcake behaviour' . Adding a foil 'hat' to my detector would just confirm this.
The Eqx still gets some EMI in this location ( plus probable hidden EMI ), and the body-block technique still works on it, so I think it would be a good test site for foil hats etc.

 

I shall try and do some experiments in the next week or so.

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I think (could be wrong...) a rough rule-of-thumb is that an opening in a conductive shield should be smaller than the wavelength of the incident wave in order to be effective.  A 2.4 GHz EM wave has a wavlength of 0.125 m (=12.5 cm = 125 mm).  That's the Eqx transmitter frequency. (Following cut and pasted from p. 67 of the Oct 2019 Eqx User Guide 5):

1723861907_Screenshotat2020-12-25155352.png.2f7f3cca950eb27c23ba3ea01ef49477.png

So does this mean that both the WM08 RF signal and the Bluetooth RF signal are strongly attenuated by a good shield whose largest opening is the size of the Eqx control module display?

(FYI, the relationship between frequency and wavelength is:  wave-speed = wave-frequency x wavelength.  Wave speed is 3.00x10^8 meters/second.)

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Is everyone who’s posting in this thread still using a wireless (Bluetooth/Wifi Stream) connection to their detector pods?? Yes, lots of external EMI is picked up by our detector’s coils,  but aside from wrapping your detector pod in a foil hat (this is something very new to me), the best thing a treasure hunter can do to incur less EMI is to utilize a headphone audio cable to their pod....Gotta minimize the unnecessary transmit/receive frequencies generated by Bluetooth and/or Wifi Streams.  I don’t seem to have any problematic issues of EMI ruining my hunts anymore since I changed to a hardwire audio cable, and turned off my machine’s Bluetooth transmitter.  When I say “ruined” hunts, I mean a hunt where I had to lower my sensitivity below 20 just to be able to tell a real signal from a noise signal.  I still keep my cell phone on while I detect, but I moved it in a hip pouch on my backside, and don’t have any issues with it now than I did months ago when I had it attached to my front (stomach area).

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Quote: "I think (could be wrong...) a rough rule-of-thumb is that an opening in a conductive shield should be smaller than the wavelength of the incident wave in order to be effective.  A 2.4 GHz EM wave has a wavelength of  125 mm."

Unfortunately not. The rule-of-thumb I use is to keep the aperture size below 0.1 wavelength, but the experts seem to prefer even smaller sizes. There's a reason microwave ovens have very small holes in the window screen. Here's one online guide, (though they are manufacturers of screening products, so are naturally going to encourage people to be thorough )

https://leadertechinc.com/blog/how-apertures-affect-emi-shielding/

So your shielding would have to be pretty good to seriously block the 2.4GHz Blutooth etc radio links, but they are pretty low power short-range links, so any attenuation may cause problems.

I'm not sure using wired headphones is going to be a better option, either. The headphone cable is an antenna, that can couple RF signals directly into the control box. There's almost certainly some RF filtering on those wires inside the box, plus you could fit a ferrite filter on the headphone cable close to the plug. Using the internal loudspeaker would be the option worth trying in bad EMI.

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15 hours ago, Raphis said:

Is everyone who’s posting in this thread still using a wireless (Bluetooth/Wifi Stream) connection to their detector pods?? Yes, lots of external EMI is picked up by our detector’s coils,  but aside from wrapping your detector pod in a foil hat (this is something very new to me), the best thing a treasure hunter can do to incur less EMI is to utilize a headphone audio cable to their pod....Gotta minimize the unnecessary transmit/receive

I never used the wireless on my Nox. Hard wired from the start. Call me old school...................

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