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On 1/16/22 12:19 PM, Mike C. wrote:

How about aluminum 'duct' tape for shielding? What are the differences compared to copper tape?

It works ok (skin depth isn't much different), but the real issue is that usually, the adhesive is not conductive.? Folks use this to make toroids for Tesla Coils, but in that application, the HV punches right through the adhesive. And, the fact that aluminum has an insulating surface film makes it tough to make good seams. However, if you do a rolled & crimped seam (hard to draw with text), it can work ok (because that makes the "slit" very long).

I've not had good luck at UHF and up, and haven't tried at lower frequencies.

The real problem is the aluminum oxide film, though.

Mike C.

On 1/16/2022 2:22 PM, N0YWB wrote:

Self-adhesive copper foil may be alternative that offers better shielding. I have used it on many plastic enclosures. I can solder bridge between sheets to cover areas wider than 4 inches.

On 1/16/22 11:22 AM, N0YWB wrote:

Self-adhesive copper foil may be alternative that offers better shielding. I have used it on many plastic enclosures. I can solder bridge between sheets to cover areas wider than 4 inches.

That's about 0.7 mil thick.? You might be able to find it with conductive adhesive - in which case you don't need to solder.? The 3M stuff is, this doesn't say one way or another, so I'd assume not.

How about aluminum 'duct' tape for shielding? What are the differences compared to copper tape?

Mike C.

Here is the one I am using for my H4.



It has some padding, and pockets for cables, etc.

...Bob / AA2FD

Self-adhesive copper foil may be alternative that offers better shielding. I have used it on many plastic enclosures. I can solder bridge between sheets to cover areas wider than 4 inches.

--
N0YWB

I like your solution, but how do you access the controls on the Nanovna? It appears they are all inside the case. What is it that I'm missing?

Thanks in advance.

Jim
KC3DPO

Jim, I've used that tin oxide for shielding of a few large products.
Visibly it's transparent which was a requirement. But I've found it's only
marginally effective, but it's better than nothing.

Dave - W?LEV

--
*Dave - W?LEV*
*Just Let Darwin Work*

On 1/16/22 9:12 AM, W0LEV wrote:

And how are you going to "shield" the touch screen?

in practice, touch screens usually have a transparent conductive layer on the top (indium tin oxide is common).? Or the actual LCD display has an ITO top electrode, and the touch screen is resistive or capacitive over the top of that, and runs at low frequencies which can be filtered (after all, you're probably not touching the screen a million times a second).

And those "thin
traces" to the SMAs? They are likely printed against a ground plane in the
layer beneath the surface layer and likely adjusted in thickness to be
nominally Zo = 50 ohms traces as stripline transmission lines. In the RF
world things are not always what they look like on first inspection.

Yes, but that transmission line still radiates a bit. Not all the field is contained in the dielectric, especially with microstripline. It's going to be a poor radiator/receiver, but that depends on what the need is.

Dave - W?LEV

On Sun, Jan 16, 2022 at 3:06 PM Jeff Green <Jeff.L.Green1970@...>
wrote:

Out and out heresy.
I'm making this a separate post because there have been several threads
covering the emi issues.

I had an interesting conversation with the ee I worked with. She explained
a bit about shielding and filtering for emi/emc.

As a rule of thumb, radiated emissions are a concern at 30MHz and above
and conducted emissions are a concern below 30MHz.

There is some overlap, but, as you go from say 100kHz up to 100MHz, you
will find the emi is caused by conduction at 100kHz and radiation at
100MHz. The transition zone depends on the physical size of the device
under test.

Devices that are physically larger will radiate at lower frequencies.

She used an example. "Say you have an object that is a 1" cube that
produces rf white noise at a constant amplitude. It won't become a problem
until high uhf because the small size simply can't radiate.

As a rule of thumb, significant radiation starts when an object is roughly
1/20 of a wavelength and almost always becomes an issue when an object is
1/10 of a wavelength in size."

The smaller an dut is, the higher the frequency has to be before radiation
becomes a concern.

She suggested I study point sources.

A NanaVNA has a USB cable and two rf cables, this is a near worst case
scenario for radiation because the cables will form the arms of a quasi
dipole.

It is extremely difficult to add enough shielding to control radiation
after a product is designed, and it's "damn near impossible to add enough
filtering adequate to control conducted emissions after a product is
designed."

The best, most effect, way to deal with emi is during the design phase.
Any effort after a product is designed will never be as effective as proper
steps during design and initial testing.

Ferrite inductors can help but, the lower the frequency of the emi you are
trying to attenuate, the more ferrite you will need.

At some point, you can't add enough ferrite to stop the emi.

She added, "Say you make your NanoVNA dead quiet, what about your PC?
Unless you have a laptop or desktop desktop that meets TEMPEST
specifications, your PC will almost certainly produce more emi then your
NanoVNA."

She looked up the NanoVNA and pointed out numerous issues. The main one is
the traces that connect the shells of the SMA connectors. For frequencies
below 30MHz they aren't an issue, as you move up from 30MHz, the narrow
traces will have enough inductance to become an issue for emi.

She is sending me an older edition of
Electromagnetic Compatibility Engineering 1st Edition, by Henry Ott. She
says it's the bible for emi/emc.

She also suggested that we not worry so much about emi because we probably
can't reduce the emi enough to be worth the effort and most likely, well
never be able to see any improvment.

She suggested we all study the manual at:


to see the steps required to really deal with emi. She also thought we'd
probably never see the difference in our test results if we were able to
make a case with perfect shielding because of the small size of the NanoVNA
and the conducted emi from the usb and rf cables.

"Far better to concentrate on a case that is robust enough to protect the
NanoVNA."

She is a smart gal, PHDs in EE and physics. Extra class ham, really smart.

"For the price, the NanoVNA is an amazing value, just don't expect the
same results you'd get with a Agilent 8563EC Spectrum Analyzer, used ones
start at 10K."

And how are you going to "shield" the touch screen? And those "thin
traces" to the SMAs? They are likely printed against a ground plane in the
layer beneath the surface layer and likely adjusted in thickness to be
nominally Zo = 50 ohms traces as stripline transmission lines. In the RF
world things are not always what they look like on first inspection.

Dave - W?LEV

On Sun, Jan 16, 2022 at 3:06 PM Jeff Green <Jeff.L.Green1970@...>
wrote:

Out and out heresy.
I'm making this a separate post because there have been several threads
covering the emi issues.

I had an interesting conversation with the ee I worked with. She explained
a bit about shielding and filtering for emi/emc.

As a rule of thumb, radiated emissions are a concern at 30MHz and above
and conducted emissions are a concern below 30MHz.

There is some overlap, but, as you go from say 100kHz up to 100MHz, you
will find the emi is caused by conduction at 100kHz and radiation at
100MHz. The transition zone depends on the physical size of the device
under test.

Devices that are physically larger will radiate at lower frequencies.

She used an example. "Say you have an object that is a 1" cube that
produces rf white noise at a constant amplitude. It won't become a problem
until high uhf because the small size simply can't radiate.

As a rule of thumb, significant radiation starts when an object is roughly
1/20 of a wavelength and almost always becomes an issue when an object is
1/10 of a wavelength in size."

The smaller an dut is, the higher the frequency has to be before radiation
becomes a concern.

She suggested I study point sources.

A NanaVNA has a USB cable and two rf cables, this is a near worst case
scenario for radiation because the cables will form the arms of a quasi
dipole.

It is extremely difficult to add enough shielding to control radiation
after a product is designed, and it's "damn near impossible to add enough
filtering adequate to control conducted emissions after a product is
designed."

The best, most effect, way to deal with emi is during the design phase.
Any effort after a product is designed will never be as effective as proper
steps during design and initial testing.

Ferrite inductors can help but, the lower the frequency of the emi you are
trying to attenuate, the more ferrite you will need.

At some point, you can't add enough ferrite to stop the emi.

She added, "Say you make your NanoVNA dead quiet, what about your PC?
Unless you have a laptop or desktop desktop that meets TEMPEST
specifications, your PC will almost certainly produce more emi then your
NanoVNA."

She looked up the NanoVNA and pointed out numerous issues. The main one is
the traces that connect the shells of the SMA connectors. For frequencies
below 30MHz they aren't an issue, as you move up from 30MHz, the narrow
traces will have enough inductance to become an issue for emi.

She is sending me an older edition of
Electromagnetic Compatibility Engineering 1st Edition, by Henry Ott. She
says it's the bible for emi/emc.

She also suggested that we not worry so much about emi because we probably
can't reduce the emi enough to be worth the effort and most likely, well
never be able to see any improvment.

She suggested we all study the manual at:


to see the steps required to really deal with emi. She also thought we'd
probably never see the difference in our test results if we were able to
make a case with perfect shielding because of the small size of the NanoVNA
and the conducted emi from the usb and rf cables.

"Far better to concentrate on a case that is robust enough to protect the
NanoVNA."

She is a smart gal, PHDs in EE and physics. Extra class ham, really smart.

"For the price, the NanoVNA is an amazing value, just don't expect the
same results you'd get with a Agilent 8563EC Spectrum Analyzer, used ones
start at 10K."

--
*Dave - W?LEV*
*Just Let Darwin Work*

Here. I look at it this way. 10% in transmission (power) corresponds to a transmitted E field 32% of the incident E field. A surface that reflects 90% of the incident power still allows 30% of the E field through, neglecting loss in the material itself. Whether that's good or bad depends on the specifics of the situation.

I'd call 10dB in power and 20dB in E-field poor shielding and 0.4 dB loss on reflection very good for an antenna. You could take another example, 50%/50%. That's 3 dB each way. We could argue ad infinitum, but In the end, it's whatever works in a given situation. Personally, I would not make the assertion you did, and that was my point. Other's can read this exchange and understand there's a difference of opinion and come to their own conclusion.

On 1/15/22 10:51 PM, Roland Turner via groups.io wrote:

On 15/1/22 23:47, 2sheds wrote:

I like the Al case, but as somebody mentioned, it likely doesn't justify doubling the price.
When will affordable metal 3D printers be available?
I guess there are work-arounds for EMI shielding that accomplish what we need.

The Sep/Oct 2016 issue of QEX contains an article on metalising the surfaces of 3D-printed plastic microwave horn antennas, the problem being working with curved shapes to improve performance over the more conventional (cheaper...) flat-surface designs that could be made with copper or brass sheet. The authors used MG Chemicals 843-340G Super Shield Silver Coated Copper Conductive Coating <> which can be obtained inexpensively from the usual electronics suppliers. The like-for-like results at 10 GHz (i.e. 3D-printing a test design using flat surfaces) were comparable to the use of foil or solid metal.

If it's good enough to be an antenna conductor, it's almost certainly good enough for EMI shielding. Note that one of the problems that the authors had was gaps in the horn and its coupler enough to see light through, which naturally leaked microwave. A complete seal might be the harder problem.

The other problem is at lower frequencies, where the spray on shield is too thin, relative to skin depth.? This is why nickel is often used - it's magnetic so the increased mu makes the skin depth shallower, so a thinner material can be used.

A lot of EMI treatments are for consumer electronics with high clock frequencies, so they're worried about VHF and UHF - hence the popularity of ferrite materials that absorb well up there. And, for 100 MHz, the skin depth is 1/10th that at 1 MHz, for the same material. So the 2.5 mils for copper becomes 0.25 mils, and a 1 mil thick layer starts to be an effective shield.

Using your numbers Lou, I would not call a 20dB reduction in E-field "very poorly as a shield". The most difficult part of using any spray is getting it in to tight corners. I''ve done "touch up" on conductive spray painted parts with a small brush and the same paint sprayed on a piece of plastic as a "pallet". You do need to work fast though.

Harbor Freight sells a small case like that as well...

73, and thanks,
Dave (NK7Z)

ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources

The following is a copy of my post of 30th August 2021 which illustrates my solution to the enclosure/connector issues:

The attached pictures show my solution to the SMA issue.

1) BNCs match all my other test gear removing the need for adapters
when interfacing.Indeed BNCs are the standard connector used for
professional test gear up to a few, GHz. (Perhaps 10GHz - Have to
check that).
2) Any risk of straining the SMA attachment point to the PCB is
eliminated.
3) The additional weight of the enclosure reduces the risk of the
nanoVNA being dragged off the workbench by the attached cables.
4) The aluminium enclosure adds a measure of screening - probably a
marginal. benefit.
5) The number of connection cycles permissible with BNCs while not
infinite, is far, far greater than the the very small number of
connection cycles specified for SMAs (in the hundreds if I remember
correctly).

The enclosure is made from extruded aluminium "U" section, readily available from eBay, with suitable apertures cut. I'm not sure that the reference planes for the BNC calibration pieces are perfect, but empirically, the results are the same as those obtained with the calibration devices supplied with the nanoVNA.

Michael. (GW7BBY/GB2MOP).

On Sat, Jan 15, 2022 at 11:51 PM, Roland Turner wrote:

If it's good enough to be an antenna conductor, it's almost certainly
good enough for EMI shielding.

I disagree with that blanket statement. The requirements and performance measurements are very different. There are a lot of variable, but for example, a surface that reflects 90% and transmits 10% of incident radiation might work very well as an antenna but very poorly as a shield.

I bought a MAX002S IP67 case from Amazon last night and it turned up this morning.
It's absolutely perfect for my use and is waterproof too.

Everything I need fits in, I've put the USB-C to USB-C cable in the back with the SMA-SMA leads and I have the calibration pieces in a little bag
too.

The foam is to cut out as it consists of little squares joined together, I've left one row to the left of the Nanovna as I will fit some SMA-M - SMA-F to save wear on the main SMA sockets and then I will remove a cube of foam by each SMA socket.

The marker data on the left does update correctly. I am unable to see the markers in the chart windows.

Ed

Hello all...
I'm not sure this is the right place to ask this, but did not find any other.
I downloaded the new version (0.3.10) and I no longer have the markers in the chart windows. Version 0.3.9 works fine. Any ideas what I did wrong?
NanoVNA H4
Windows 10 64 bit
Thank you.

Ed

MIL-SPEC is applied to an item that meets or exceeds the Milatary specifications that is effect for that product being made.
The Company I worked for built products for the military. Power supplies for Amram, HV power suppies for several Headsup displays on Milatary Jets and Subs, as well as power converters and magnetics for most every Air plane manufacturer in the Free World.
Retired Electronics Manufactureing Engineer of 35 years at OECO LLC, Milwaukie, Oregon
Clyde Lambert KC7BJE