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#1
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Source for RF "pass-through"?
Could it be a feed through capacitor? This is a short from one side of the
wall to the other, but it has some capacitance to ground. The purpose it to pass DC but shunt high frequencies to ground. Very useful for passing DC power supply voltages through a chassis wall. A picture and price are he http://www.oselectronics.com/ose_p95.htm Al KA5JGV "DaveC" wrote in message al.net... Not sure of the proper name, but I'm looking for a connector that provides connection through a bulkhead, from one PBC to another PCB. Not a "connector" in the traditional sense. Both sides of it look like the back end of a solder-type connector; just someplace to solder a wire. I've searched Digi-Key, Mouser, and a few others, but can't find anything like this. I've seen them in hi-f comm equipment. I need one for 2.4 GHz. Where can I find one? Thanks, -- DaveC This is an invalid return address Please reply in the news group |
#2
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I guess that won't do for my purpose. I'm trying to do just the opposite: preserve the RF while passing it through a hole in the shielding. It only has to span about 3/4 of an inch (17mm?). What's the best device for this purpose? 17 mm of coax. RF doesn't like to go thru little holes. W4ZCB |
#3
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17 mm of coax. RF doesn't like to go thru little holes.
OK, coax it is. Can I use coax without the outer poly jacket? It would make it much easer to solder in that small space if it were not there. It can be used without the outer insulation, as long as you make sure that the braid doesn't accidentally touch anything which isn't supposed to be part of the RF ground. In fact, if you're using coax to create a feed-through into a shielded, grounded subenclosure (e.g. one made out of scrap PCB material soldered to the main board's ground plane) then it would probably be a very good idea to remove the outer insulation, feed the coax through a hole in the enclosure wall which is just _barely_ big enough, solder the ends into place, ground both ends of the braid, and then also solder the braid to the subenclosure wall where it passes through. A more standardized way of creating such RF feedthroughs is to mount an SMA connector on the subenclosure wall - solder minicoax to one side of it (often the inside), and use a flexible or mini-hardline coax with an SMA plug to connect to the other side. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
#4
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By the way... They used to also make feed through thingies that didn't include
capacitance. But a 3/4 inch wall would exceed their capability. Oh, and at 2.4 Gigs, 17 mm of coax will look like a transmission line. Bill, K5BY |
#5
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In article et,
DaveC wrote: A more standardized way of creating such RF feedthroughs is to mount an SMA connector on the subenclosure wall - solder minicoax to one side of it (often the inside), and use a flexible or mini-hardline coax with an SMA plug to connect to the other side. So make a male-female connection? Right. Mount a female SMA jack on/through the wall (solder it, for best shielding and grounding), connect coax to its rear connector inside the subenclosure, and use a male SMA on the cable which connects to it on the outside. I'm trying to preserve as much of the signal as possible. This will lose a few dB, won't it? Great Ghu, I should certainly hope not! Unless you create a really severe impedance mismatch when you connect the coax, almost all of the power will get through without being either reflected or absorbed. You shouldn't lose more than a very small fraction of 1 dB if you do it right. This sort of hookup approach appears widely throughout the excellent "Experimental Methods in RF Design" book by W7ZOI/KK7B/W7PUA, available through the ARRL. In this book it's quite common to see modules such as local oscillators and bandpass filters being constructed inside sealed enclosures, with the power going in via the capacitive feedthroughs someone else mentioned, and signals going in and out on SMA connectors (or BNC if you've got the space and want to save a few bucks). You'll also see this approach used in commercial microwave gear. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
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