[SOLVED] 0.6mm PCB, how flexible? - Page 1
Forum section: electronics / projects

author: CJay
author_rank: Super Contributor
timestamp: January 31, 2021, 01:05:55 pm
content: MOSTLY SOLVED!! I have found an article I saw a good few years ago, contains details of how to make window passthroughs with a strip of aluminium and gives basic information on how to dimension/adjust it for 50R, there's also a method using a laminator pouch to create a 50R stripline which could work too.I want to try and create a 50R impedance flat flex or PCB that's capable of handling ~100W RF to pass between a side hung window and frame.It's not possible to drill holes in the frames, walls etc.How flexible is 0.6mm PCB or do I have to think about a custom flat flex (or off the shelf if you know of one?)?

author: daqq
author_rank: Super Contributor
timestamp: January 31, 2021, 01:40:39 pm
content: A 0.6mm is not flexible enough for this, unless you have REALLY weird windows. What's the worst angle/curve it would have to bend? What's the profile you have to adjust to?There are some very thin coaxes/rigid coaxes out there, not sure about their power handling, but it might be worth checking them out.

author: Yansi
author_rank: Super Contributor
timestamp: January 31, 2021, 01:41:27 pm
content: Sorry, but 0.6 mm is not a flexible PCB. IF you need flexible, order a flexible one. That is a completely different substrate material (typicaly Kapton with about 0.1 mm or less thickness) for the flexible PCBs.

author: Yansi
author_rank: Super Contributor
timestamp: January 31, 2021, 01:42:55 pm
content: And there are also special RF coax pieces designed to be squished in a window. But usually designed as 75 ohm, for a TV/SAT broadcast systems.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 31, 2021, 02:09:33 pm
content: Could you capacitively couple through the glass, or is it double glazed?ISTR this was used for in-car mobile phone antennas when fitted carphones were a thing

author: thinkfat
author_rank: Unknown
timestamp: January 31, 2021, 02:52:15 pm
content: Capacitively coupling 100W through a window, sounds like a great plan.

author: CJay
author_rank: Super Contributor
timestamp: January 31, 2021, 03:38:17 pm
content: Ah well, nowhere near flexible enough then, thanks for the answers.I'll explore other ideas, I've seen this done with thin aluminium sheet that was dimensioned for 50R impedance, I guess I could do the same with thin brass or copper.I've seen capacitively coupled antennas, they aren't awful but I think 100W would be a stretch for a single pane of glass and these windows are double glazed so no chance.Might be worth exploring the idea of a proper flex PCB, after all the commercial versions of this idea are $50

author: Yansi
author_rank: Super Contributor
timestamp: January 31, 2021, 04:29:01 pm
content: If you think you will make a flex PCB cheaper yourself, I have some bad news for you then.Buy something like this and forget about the flex PCB idea.https://www.americanradiosupply.com/comet-ctc-50m-flat-window-door-feed-thru-coaxial-cable-so-239///EDIT: This stuff looks like a bare flex PCB on Kapton. But mind you, it is 75 ohm and for receive levels only, as it more than likely uses a pair of baluns to transform from the coax to the balanced line.https://www.americanradiosupply.com/flat-window-feed-through-flexible-rg-6-coaxial-cable/

author: CJay
author_rank: Super Contributor
timestamp: January 31, 2021, 07:27:06 pm
content: Quote from: Yansi on January 31, 2021, 04:29:01 pmDefinitely wasn't intending to try making flex PCB at home, I have seen articles showing home made window passthroughs made of parallel strips of aluminium dimensioned for 50R, no baluns required.That Comet item is definitely not 75R nor is it RX only, it's specified as 50R,100W PEP and I don't think it uses baluns either.I could also use a short length of RG316 which should be good for more power than I have available