Equinox Emi Solved???

[Joe D.]

   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 headphones being directly connected to the pod, where it gets in the way!

   And i've had no real issues with hard wired, as i used to have with the wireless headphones!👍👍

[GB_Amateur]

4 hours ago, PimentoUK said:

The rule-of-thumb I use is to keep the aperture size below 0.1 wavelength,...

So over the years I lost track of the decimal point?  😁  Thanks for pointing that out.  Another example (besides your microwave oven 'window' covering -- a good one) is comparing radio telescope surfaces to those on optical telescopes.  The latter (optical) need to be smooth to 1/4 wavelength (for amateur instruments) and smaller (for professional instruments) and thus appear flawless to our naked eyes since their sensitivity is to EM radiation of less than a micrometer (millionth of a meter).  The former (radio) are reflecting long wavelength light (wide range but think centimeters) and are typically made from metal screens.

 

[Raphis]

8 hours ago, Joe D. said:

What i did change on a few of my detectors is running an extension  to the rear, under the arm cuff!

That’s exactly what I did on my Nox.  Works well for me.

[Cal_Cobra]

I'm going to order a cheapo control box cover and line it with foil, or maybe I can get some kind of RF shielding material from work...hmm.

@PimentoUK Do you think a control box cover lined with this would do the trick? 

https://www.ebay.com/itm/EMF-RF-RFID-Shielding-Nickel-Copper-Fabric-Folded-12-x-43-of-Material/174128886930?hash=item288ae3f492:g:74UAAOSw0ItbpZ4N

I have a couple of intercity spots that are infested with EMI, mainly from unshielded overhead high voltage Muni electric bus power cables that would provide the perfect test ground for a RF shield.

[PimentoUK]

It all sounds rather expensive, over-engineered and unnecessary, in my opinion. I'm planning on making mine from the thick foil that's used ( in my country .... ) for ready-prepared food. ( peel off film lid, place in oven for 45 minutes sort of food ). Then just spray paint it black so it doesn't garner attention.

Gotta say that eBay listing comes with a surprising quantity of technical info on shielding, which makes a change. So many listing contain masses of legal/contractual/ T & C stuff, whilst telling you nothing about the product.
I haven't made or tested my 'foil hat' yet, yet another infuriating lockdown means going out and testing it is a bit risky, though I have another alternative location that's more accessible.

[Joe D.]

Thanks Cal for locating the fabric! I think i may try that out myself! Great find!👍👍

[GB_Amateur]

16 hours ago, PimentoUK said:

Gotta say that eBay listing comes with a surprising quantity of technical info on shielding,...

I like that feature, too, except I question its accuracy.  Here is a link to Wikipedia article which only mentions capacitance in one place.  From what I know you don't need to make a capacitor.  (My knowledge is only for the electrostatic case, though.  EMI is electrodynamic which tends to be more complicated.  Things like skin depth enter the picture -- think eddy currents in a USA clad coin where the copper inner layer dominates and thus gives a high VDI.)  I think one layer of conductive material is sufficient if properly implemented.  Possibly their double layer of conductor separated by an insulator/dielectric (thus forming a capacitor) is a way of making a more lightweight shield, though, compared to only one thicker layer of conductor.

[PimentoUK]

Mr. Nox's shiny hat is part-made, I've 'finished' the foil screen.  I'd like to say how fine he looks in it, but unfortunately the aluminium soldering did not go well, there's some ugly-looking grey blobs instead. The thick foil sapped too much heat from my iron, which isn't that hot anyway. I didn't prepare the joint area, either; I'm sure rubbing it with fine aluminium oxide abrasive paper ( or possibly a glass-fibre pencil ) cleans off the oxide film and helps the solder wet the surface. Oh well.

It's made from 0.1mm thick foil from a large pre-prepared food tray. It's one piece of foil, about 290mm x 160mm, folded up and soldered in a few places. With a hole for the headphone connector, and notches for the PP button and the coil cable.

For info, the solder I used was Multicore Alusol 45D:

https://cpc.farnell.com/multicore-solder/629443/solder-alusol-0-91mm-500g/dp/SD00059

It used to be available in a tubular plastic dispenser of 1.5 metres, at a realistic price, but now only seems to be sold as expensive 500 gram reels. However ( in the UK ) there are eBay sellers listing small packs of 1 metre lengths, maybe in your country similar deals can be had.

Update: I've now finished the USB port ground-connection part. I over-engineered it, but the end result is OK. A little spring-pip just like on the Minelab USB plug, soldered to a bit of copper sheet and a length of 3mm tapped pillar make up the electrical part, giving a short direct connection between detector ground and foil screen. The plastic housing ensures the pip lines up with the USB port pad, the two steel screws line up with the magnets to hold it in place, quite firmly.

The foil hat will have a 3mm hole made in it, and a M3 stud attaches it to the ground adapter.

[GB_Amateur]

48 minutes ago, PimentoUK said:

...Unfortunately the aluminium soldering did not go well....

Soldering aluminum is a tough task to say the least.  They make conductive epoxy which works well for such an application.  (I don't have any in mind or I'd post a link.  It's been quite a few years since I used it, and my memory ain't what it used to be.)

[midalake]

****UPDATE****

I made an aluminum shield out of tape that goes over my cover and can be removed.  I have the same EMI outcome. No EMI from cell phones and NO EMI from that communications equipment. 

Dave