That's silly. If it's a coupling cap, it doesn't matter. If it's a bypass, it doesn't matter. It might, rarely, matter in something like a filter.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
John Larkin wrote
So it is like some HiFi audio recorder with DCcoupling...
I did that when I started playing with FPGAs, for short waveforms, and video. You can make a nice testcard that way too. Still have a FPGA extention board with an old video DAC.
F35s too? Maybe fiberglass absorbs radar?
But seriously, it is the soldering (not even 60/40) that worries me there, bad joints on parts that receive external forces is a common fault.
So, if the LO leaks a little bit into the RF around your mixer, and the antenna of the receiver is activated by it, your radio is transmitting a bit of that LO so the opposing force can find a target for their artiller y.
It DOES matter, rarely. Once in a lifetime, perhaps. Military commo protocols include not only 'radio silence' meaning no transmission, but also 'listening silence'.
"Outside foil" means a big film cap. You wouldn't use that for RF. Surface-mount ceramics don't have foil, inside or outside.
A stealthy military box had better be seriously shielded. If PCB parts radiate enough to be dangerous, get a better engineer.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
No, but I reckon carbon fibre reinforced plastic would/could.
Ok. I yield. You're right. It doesn't matter with what you are probably doing.
I did have some odd problems with non-polarized capacitors, where the can is usually connected to the negative terminals of the two back to back capacitors inside the package:
I also had a problem with filtering in an open frame switcher with a negative voltage output. The pos terminal was grounded and the can negative was connected to the power supply output. It coupled some switching junk into some nearby high input impedance circuitry. I couldn't find an electrolytic with a postive can so I fixed it with a grounded extra foil shield around the electrolytic.
However, neither of these problems appear to be anything you might run into in your product.
Adding fuel to the fire: Tantalum electrolytic capacitors with solid electrolyte are marked at their positive terminal with a bar or a "+". Tantalum electrolytic capacitors with non-solid electrolyte (axial leaded style) are marked on the negative terminal with a bar or a "-" (minus). The polarity better can be identified on the shaped side of the case, which has the positive terminal. The different marking styles can cause dangerous confusion. A particular cause of confusion is that on surface mount tantalum capacitors the positive terminal is marked with a bar. Whereas on aluminium surface mount capacitors it is the negative terminal that is so marked.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
We buy surface-mount aluminum caps that have a plastic base header that has bevels that define the orientation.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Not every manufacturer uses that style of polarization marking:
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
We usually buy this style of alum or polymer caps:
and tantalums like
I haven't tried tantalum polymers. The regular ones have ESRs that are about right for bypassing regulator outputs.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
The outside electrode ought to be marked, but it needn't be foil (it isn't for an electrolytic in a can, nor for a tubular ceramic) nor need it be big. Some of my HV oil-filled caps, it matters a LOT which end is near ground. MLC ceramics DO have outer plates, but I don't recall seeing indications in the markings (not that robotic assembly could read 'em).
I know engineers who do that kind of work...they shrug and change the subj ect every time the topic is mentioned.
Polymer chip caps are (marked at the '+' end). I've seen aluminums marked at the positive, too, but they're marked with a plus sign.
It's a lot easier to avoid radiation than to keep the radiation inside.
These are marked on the negative end:
Everybody should use + signs.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Not talking about cans pretending to be SMT. I'm talking about the SMT chip style.
Mharharhar... }:->
Best regards, Piotr
Tupperware cars. Luxury!
NT
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.