How to connect antenna base to powder-coated steel?

[Joerg]

[...]

You've got to be kidding. I ran a place
with production for several years

You must have failed at it, since you are not still doing it.

Ever heard that companies can be _profitably_ sold?

Do you live in a cave?

Sounds like a deeper, stupid Mfgr with stupid processes in place to
start with. Boilerplate stupidity begets boilerplate stupidity.

Then obviously another company wouldn't have bought us. Yet they did.

Not enough to know that you do what must be done to get to the finish
line.

Oh, we will get there, we always do. Just not with 4h curing times.

[...]

 

[My Name Is Tzu How Do You Do]

Oh, we will get there, we always do. Just not with 4h curing times.

[...]

You will have them if you ever need to implement the silver filled
epoxy to facilitate a design.

Our BGAN portable radio has a fully hogged out Aluminum chassis. Well,
each of the elements are fully hogged. THEN the get assembled into the
finished box. Despite proper screw spacing and full mil spec level EMI
chassis design elements being used throughout, it still failed Tempest
emissions test miserably. At first, we had to hand fillet all the side
wall and base plate seams with the epoxy. Then, they barely passed.
Tempest emissions specs are VERY strict. Now, we have the metal shop
vendor making them for us place the epoxy beads in the seams at assembly
time, and they bake them before and after the powder coat sequence.

They did not piss and moan over several long bead placements AND an
extra 4 hour cure cycle, yet you want to cry because of your convoluted
semi-educated mindset about manufacturing processes. As a result, the
radios pass muster, because the chassis is finally truly sealed against
releasing any of the internal radiations being grabbed.

4 hours of cure time is NOT 4 man hours of ANYONE's labor, idiot.
Learn how to analyze a process correctly. You'll look more competent.

 

[[email protected]]

Four hours at 80C is "nothing"? You've got to be kidding. I ran a place
with production for several years and turned that division around to
profitability. So I know a thing or two about production, and 4h at 80C
does not fly with large sheet metal items.




That leaves the bare unplated steel. Meaning we'd have to pot that up
later and that is a highly undesirable step in system assembly. Then
we'll rather go the stainless custom bracket route. Less $$$.

I haven't been following this thread, but when we've needed a conductive
metal-to-metal contact (EMI reasons, normally) we masked off the powder coat
and nickel plated the area. It wasn't at all expensive.

 

[Joerg]

Oh, we will get there, we always do. Just not with 4h curing times.

[...]

You will have them if you ever need to implement the silver filled
epoxy to facilitate a design.

Our BGAN portable radio has a fully hogged out Aluminum chassis. Well,
each of the elements are fully hogged. THEN the get assembled into the
finished box. Despite proper screw spacing and full mil spec level EMI
chassis design elements being used throughout, it still failed Tempest
emissions test miserably. At first, we had to hand fillet all the side
wall and base plate seams with the epoxy. Then, they barely passed.
Tempest emissions specs are VERY strict. Now, we have the metal shop
vendor making them for us place the epoxy beads in the seams at assembly
time, and they bake them before and after the powder coat sequence.

They did not piss and moan over several long bead placements AND an
extra 4 hour cure cycle, yet you want to cry because of your convoluted
semi-educated mindset about manufacturing processes. As a result, the
radios pass muster, because the chassis is finally truly sealed against
releasing any of the internal radiations being grabbed.

BGAN is used in the heavy duty and mil world. Very different market. Of
course nobody will moan about a few bucks more. For much of my designs,
very different thing.

4 hours of cure time is NOT 4 man hours of ANYONE's labor, idiot.
Learn how to analyze a process correctly. You'll look more competent.

Has it occurred to you that industrial real estate is not free? That
curing ovens are not free? Do you know what overhead costs are and how
they get charged to departments? It appears you need to brush up a bit
in those areas.

Oh, and I am sure that in your miraculous world there are elves who
bring the panels to and from the curing ovens without any pay
whatsoever. Unless, of course, they are union elves ...

 

[Joerg]

I haven't been following this thread, but when we've needed a conductive
metal-to-metal contact (EMI reasons, normally) we masked off the powder coat
and nickel plated the area. It wasn't at all expensive.

T'is exactly what I suggested and the shop turned that down :-(

 

[Joerg]

I've used epoxy that was hard in something like 5 minutes

Me too, but it is definitely no fun. Even the 15 min stuff I often use
is a pain. You mix it up hurriedly, work, and 5-10 mins into the game
the stuff already begins to gunk up.

Then there is epoxy that is activated, for example by UV. But such
processes are highly undesirable in the usual production environment
unless the shop is already geared to do that. Then the fire marshal
comes along and mandates a fume hood. Then the enviro guys show up and
say you are polluting the air, causing polar ice to melt or whatever.
Lots of bureaucracy and extra cost, BTDT. Best to avoid this stuff

 

[Spehro Pefhany]

Gents,

Ran into a wee snag during a design. The metal enclosure is plain steel
that is powder-coated. The guys at the metal shop said that they cannot
provide a nice connection surface for a bulkhead connector like this:

http://www.l-com.com/item.aspx?id=5295

I was hoping they could provide a masked nickel-plated area but ...
nope. They can only provide a threaded stud like those safety ground
ones. Not so cool at several GHz. Ok, we could make a wide shunt strip
for that but that's yet another custom BOM item. Corrosion is also a
major concern here since this gets deployed in coastal regions. So
straight bolting onto bare steel is out.

Anyone know of a clever way to handle this? If someone knows of a
cheaper bulkhead SMA feedthrough connector that would also be nice. Four
bucks is a bit steep.

Can you get them to spot-weld a standard nickel-plated washer to the
case?


Best regards,
Spehro Pefhany

 

[Joerg]

Joerg ...

2.5 gig is where I cut my engineer baby teeth right out of college and
for the next five years. I hadn't worked above 300 Meg before that.
Paint a better picture of what you are trying to accomplish and I'll
bet I can do the whole thing for less than a Lincoln bill.

Well, I almost have this project wrapped up by now (except for the
layout). Found an extension cable that can be panel-mounted. Looks like
gold-plated brass so we'll just have a strip made that has two holes. A
big hole that goes under this bulkhead connector and a small one that
goes onto the stainless stud right next to it. I just haven't made up my
mind whether to use stainless or brass for the strip, it's very close on
the galvanic table. I guess brass is much easier to machine.

Not ideal but low enough in inductance.

It'll be RP-SMA, then there's a much better selection of antennas.

Is it raining up in your area already? Dry down here but cold, the wood
stove has been going all day.

 

[Joerg]

Can you get them to spot-weld a standard nickel-plated washer to the
case?

Good idea. When I hand the design over to the client tomorrow I'll ask
them to check into that. Although I am not too optimistic after their
metal shop turned down the fairly standard Ni-plating request.
Unfortunately it's all a bit cost-sensitive so changing shops isn't
always in the cards here.

 

[Joerg]

Joerg wrote:

[...]

Is it raining up in your area already? Dry down here but cold, the wood
stove has been going all day.

P.S.: The rain is now here. Yay!

 

[My Name Is Tzu How Do You Do]

BGAN is used in the heavy duty and mil world. Very different market. Of
course nobody will moan about a few bucks more. For much of my designs,
very different thing.

AGAIN, you fucking retard, the metal shop had no problems with the
operational requisites.

You need a few billion more functioning neurons, and about 65 more IQ
points. The second more than the first.

 

[My Name Is Tzu How Do You Do]

Has it occurred to you that industrial real estate is not free? That
curing ovens are not free? Do you know what overhead costs are and how
they get charged to departments? It appears you need to brush up a bit
in those areas.

Like I said, you're too much of a goddamned crybaby to perform
manufacturing processes efficiently or intelligently, much less know how
to. THEN, there is the overt stupidity issue piled on top of that. Sad.

 

[My Name Is Tzu How Do You Do]

Oh, and I am sure that in your miraculous world there are elves who
bring the panels to and from the curing ovens without any pay
whatsoever. Unless, of course, they are union elves ...

Let's see. The oven here is about 20 feet from my cubicle. The
assemblers have no problems getting to them or from them in a matter of
seconds.

Only retarded crybaby bullshit dumbfucks like you inflate costs as a
mechanism to subdue advancement.

A 15 second trip to the oven, and 15 seconds back to the bench is not
even able to be tallied... except by total retards like you.

Then, there is that deal where if you had ANY brains at all, you would
place them in there overnight on an oven with a timer, and retrieve them
in the morning.

It don't get much dumber than a twit like you, nit picking over total
bullshit.

I would have spotted your stupidity from the get-go, and you would
never have gotten those 'years of experience" fixing up an obviously
already fucked up manufacturing floor.

Oh boy! Any movement would have to be positive in a set-up that fucked
up. After all, they were so desperate they put you in the spot.

My dog could have made it run better.

 

[My Name Is Tzu How Do You Do]

I've used epoxy that was hard in something like 5 minutes

-Lasse

Yeah, and your grasp of covalent and cohesive bonding principles, much
lees the materials used is right at NIL, you stupid ****.

ANY 5 minute epoxy will NOT adhere to bare steel, and barely 'stays' on
painted surfaces. It ages and is generally NOT meant for ANY industrial
setting, EVER.

You need industrial grade epoxies at the bare minimum. Like 3M's DP190
or DP460.

Even those are brittle in nature though. The conductive epoxy was
suggested because it does what is needed. Yes, most advanced epoxies
require thermal cure. Most that do not are not that great at performing
under pressure.

 

[My Name Is Tzu How Do You Do]

Can you get them to spot-weld a standard nickel-plated washer to the
case?


Best regards,
Spehro Pefhany

You cannot spot weld onto powder coat, and if you do it bare, it gets
powder coated afterward. Doh!

 

[Spehro Pefhany]

You cannot spot weld onto powder coat, and if you do it bare, it gets
powder coated afterward. Doh!

Of course it would be done before the powder coat.

Masking, such as precut silicone-adhesive polyimide discs would be
applied, and they are rated to easily withstand the typical 200°C
curing temperature for the powder coat.

http://www.maskingproducts.net/Low-static-Polyimide-Masking-Discs.php

Lots of sources for these things.

I actually thought that bit was too obvious to bother mentioning.


Best regards,
Spehro Pefhany

 

[miso]

No, a big custom steel box with a steel lid on top.

But it should be a NEMA box. Or built to such standards.

Ok, but we do not want the metal to be out of the equation. We'd like a
low-inductance connection to this steel lid.

You never really get a low inductance connection at GHz frequencies. You
are far better off shielding the parts of the PCB that need to be shielded.

Pigtail isn't a great ground at GHz frequencies. Feedthrough without
connection will work but results in the coax shield picking up noise
from the electronics inside.

A pigtail IS a feedthrough without a connection. You have coax hanging
from the box with a connector. Personally I don't like that scheme
UNLESS I can open up the box and replace the coax. But it is very common.

Antenna with pigtail:

 

[Joerg]

Let's see. The oven here is about 20 feet from my cubicle. The
assemblers have no problems getting to them or from them in a matter of
seconds.

And your products are what, taxpayer financed? Cost-plus? Well, ours aren't.

[...]

My dog could have made it run better.

I sure hope you are nicer to your dog than to people here.

 

[Joerg]

But it should be a NEMA box. Or built to such standards.

The box has to be full custom because there's also some big gear and
plumbing in there. Unfortunately also controllers in plastic enclosures.
But it's quite weather-proof.

You never really get a low inductance connection at GHz frequencies. You
are far better off shielding the parts of the PCB that need to be shielded.

Can't. It's a retrofit situation where my stuff has to be installed as
an upgrade on thousands of units, and after that new units but they
don't want to redesign the controllers. Those are in plastic cases
inside so there will be some radiation of RF, potentially messing with
our RX function. The noisy stuff will be well shielded.

The inductance does not have to be zero, low enough is good enough

A pigtail IS a feedthrough without a connection. You have coax hanging
from the box with a connector. Personally I don't like that scheme
UNLESS I can open up the box and replace the coax. But it is very common.

Antenna with pigtail:

That's a Yagi, that won't need RF-proof grounding. We only have a rubber
duck antenna, max allowed per FCC is 2dBi, plus no more space. This
needs (somewhat of) a ground plane, else the coax inside would become
part of the antenna and pick up stuff.

 

[Joerg]

Of course it would be done before the powder coat.

Masking, such as precut silicone-adhesive polyimide discs would be
applied, and they are rated to easily withstand the typical 200°C
curing temperature for the powder coat.

http://www.maskingproducts.net/Low-static-Polyimide-Masking-Discs.php

Lots of sources for these things.

I actually thought that bit was too obvious to bother mentioning.

To me it was obvious

Have asked but no response yet. Looks like lots of bulkhead stuff is
(thinly) gold-plated brass these days. Gold is zero on the galvanic
table so I hope it'll be ok. The brass would be. Now a big Ni-Au plated
washer, that would look really cool. But with gold being at $1654 that
probably isn't going to fly.