Filters for VHF/UHF - prototyping on glass? - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: May 10, 2020, 02:14:28 pm
content: A nice thing about copper tape is that you can change it easily with a hobby knife. Ive made some antennas with foam core and copper tape and that works well, as long as you put whatever has to be soldered for any time on a piece of PCB. Don't try to solder to copper tape on foam core unless its just a tiny connection and its done instantaneously. I've actually only tried it once.What about glass? Would glass be enough better for making filters that it would be worth doing it? I am thinking about the 2000-6000 MHz range. Am I correct in guessing that its maybe the cheapest low loss material that most people are likely to be able to find without a lot of fuss. teflon is not good because of soldering and fumes. Glass seems ideal for prototyping stuff like filters on. I could buy some wide components and use glass thickness that was appropriate for whatever tape width I was using and .. I dont know. lack of vias would be a PITA, I suppose.. maybe its not such a good idea.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: May 10, 2020, 03:49:13 pm
content: Depending on the permittivity you want, I would argue that sheets of HDPE would arguably be the cheapest option. HDPE is practically identical to PTFE, just an order of magnitude cheaper. (and, if you get very pure forms, according to some sources even lower loss than PTFE). Styrofoam could also work, with an even lower permittivity (I suspect, for all intents and purposes, practically a relative permittivity of 1).I think model shops also stock sheets of solid polystyrene, but I don't know what the loss of that is?Ofcourse, the problem with all of these is that you can't really solder to them.Glass might indeed be a good option. Wonder if you can get something like big microscope slides?Perhaps some kind of ceramic, porcelain or such, would also work?I do wonder if there is some kind of screw-on connector you could use with non-solderable materials. I know we use them for our measurements, but I imagine you can build something like them too?

author: coppercone2
author_rank: Super Contributor
timestamp: May 10, 2020, 10:55:50 pm
content: careful bonding to glass, super glue is no good, if you read 3m literature, it was described as being initially very strong, but later failing for no reason (explained by some technical mumbo jumbo). The loctite glass bonder sold in hardware stores looks like regular super glue, but according to the SDS its abutylbased super glue (most are ethyl or methyl).low energy plastics like PE or TF require primers for stuff to stick. They have primers for tape too.https://www.3m.com/3M/en_US/bonding-and-assembly-us/applications/material-bonding/traditional-materials/

author: profdc9
author_rank: Frequent Contributor
timestamp: May 13, 2020, 10:34:14 am
content: Polyethylene can be "flame treated" so that you can stick to it. Basically, you take a butane torch and you pass the flame over the surface of the polyethylene. Not enough to melt or char it, but you create polar bonds on the surface that the adhesive can stick to. You will notice that if the PE has a glossy surface that the surface is no longer glossy after you flame treat it. I have used this method to stick blocks of PE together with 2-part epoxy and make high voltage bobbins for transformers.You might be able to flame treat the polyethylene and get copper tape to stick to it. Some cutting boards that are made from HDPE and are amenable to this. You can also get sheets of 1/4 inch HDPE from Small Parts or other plastic supply.The only adhesive I know that sticks reliably to glass is silicone. It works very well (it is used to assemble aquarium panels together) so you might be able to take thin sheets of copper foil and glue them onto the glass using silicone adhesive. Do not use the stuff with the vinegar smell, because that will attack copper readily, perhaps the methanol-based silicone is better.