Found this picture of a RF? choke on the coil cable of a metal detector, wondering ...

[Polymer]

Found this picture of a RF? choke on the coil cable of a metal detector on the bay.

Since I have not seen this on coil cables before I am wondering if this
might help cutting down on EMI - or is it just wishful thinking?

Here's the pic:

[Koala]

Wishful thinking

EMI is picked up by the coil its self

If they worked every manufacture would fit them as standard.

[homefire]

Yes in fact it can and DOES cut down on some EMI and RFI noise. Just as they do on any other products used on. This subject was posted on some place in here on the forum.

""Wishful thinking

EMI is picked up by the coil its self ** Yes as well as the Connecting Cable. That does not mean it has to be allowed to pass on to the circuitry. They work like a LOW PASS Filter.

If they worked every manufacture would fit them as standard."" ** Most detector circuits are not running critical enough to warrant the use. Cost would also play a part even if they only cost pennies.

[Qiaozhi]

Perhaps someone should run a test to see if the RF choke has any effect, but personally I doubt it since the choke has been placed around a shielded cable.
The picture also shows a coil from a VLF detector, which will inherently filter out any RF, as it will be tuned to the TX frequency.

[Koala]

http://www.dankowskidetectors.com/di...?2,16807,16832

[Koala]

Reading through the forums several people have said they do nothing at all.

Two have had a positive affect with the bead by the coil. I suspect the null of the coil is being affected by the ferrite as this is the way I adjust the null after its been potted.

[homefire]

Maybe the one in the photo is not using Shielded wire and that's why they employed one ! Again most detector circuits really are not running that critical of a circuits. The Bead only work at higher Frequencies and would not be effective in the lower EMI ranges. We have one of those airostat radar blimps here just out of town. When they have it turned of I can hear the Blip on my Whites Prizm quit well some times. That signal is probably getting strait into the PCB never mind coil and cable. The blips come at about a one second interval. I don't think they would be effective for something like that. http://www.analog.com/en/analog-dial...mystified.html

[Koala]

Looks like the standard Whites XLT coil. Just with a snap on bead added

[kt315]

vlf whites coil has RC filter inside on RX side. its enough. do you need yet protection? for what? that will give you more depth
or still one subject to tweet in dankowski bla-bla-bla?

[ionut_mtb]

check this gs5 using ferrite choke on main battery cable. I think is one of Alexandre modified detectors.

[Carl-NC]

The purpose of the choke isn't to reduce incoming EMI, it's to reduce outgoing EMI. They are sometimes added to pass EMI compliance testing for FCC and CE.

[kt315]

boom boom boom. what says physics Carl? it's reduce both directions just the choke does not have homo sapiens's mind
to choice right direction.

[Idefix]

In fact, if the bluebox is the battery, and yellow the PI mainboard, the main generator of interference is the PI itself.
On the supply wires, the PI will not be perturbated by some few µV/m coming from external , (but may be by v/m due to proximity of cell phones. .)
The PI will generate EMI on these wire , for sure, and a ferrite can help. Generally ferrite like that only gives a 3db boost margin on the CE rules.

[Carl-NC]

boom boom boom. what says physics Carl? it's reduce both directions just the choke does not have homo sapiens's mind
to choice right direction.

The reason the choke is added to get the detector's EMI below the FCC/CE regulatory mask. It may also reduce incoming EMI, but that effect is generally too small to make any difference, and that is not its purpose.

[Qiaozhi]

The reason the choke is added to get the detector's EMI below the FCC/CE regulatory mask. It may also reduce incoming EMI, but that effect is generally too small to make any difference, and that is not its purpose.

Does the ferrite really provide any reduction in EMI if it's clamped around a shielded coil cable?
I've never tested it, but it seems to me that it would have a negligible effect, if any.