Name of coax ground isolation device?
I looked for a "coax isolator" but that is something else entirely. A "DC block" only blocks the center conductor. If I knew what it is called I am sure I could buy one somewhere.
Thanks
The best way to block low-frequency and DC on the coax sheath (including center conductor) s to use a pair of waveguide-to-coax transitions, and use a thin Teflon foil to separate the waveguides. Foil thickness to be determined by expected DC voltage- a 10 mil foil can hold >100 V. I doubt anyone makes a commercial device, but the transitions are available.
If your system is WiFi, you can send both up and downlink by antennas- at 2.4 GHz WiFi range is typically up to one kilometer, and this way the solution will be much cheaper. Patch antennas may suffice for a short distance like meters...
I would simply use two coax connectors, with a capacitor (100pF or so) in both signal and ground connection.
Are you looking for a "Bias Tee" ? That blocks DC and passes RF signals only?
I was hoping this was a common enough problem I could just buy a weatherproof widget to screw onto the SMA connectors, like they do with video isolation transformers to block ground loop hum bars.
The waveguide solution is elegant but much too expensive. I will probably make something with capacitors.
Not just a Bias Tee as I need to block the shield as well.
He doesn't need to feed any DC, so his "DC block" was fine ... except that it isolates only the center conductor and not both signal and ground.
So we are looking for a DC-block that has capacitors in both signal and ground path. Normal coax devices all have a continuous shield (for good reasons), so it seems we need a homebrew solution. Two coax connectors with series cap in both signal and ground path will work fine.
Some sort of ferrite bead transformer would work at lower frequencies, but I am not so sure at 2.4GHz.
There are ferrite transformers for 2.4GHz, but they usually have a different configuration that doesn't block DC path from input to output http://194.75.38.69/products/Transformers.shtml
And the packaged ones will again have common ground for the coax connectors. It is very unusual in RF to isolate/float the return path.
? ferrite beads? come on. outside dc block!
http://www.pasternack.com/outer-dc-blocks-category.aspx
you could do it with waveguide where the flange had a choke joint, the guide faces were insulated using kapton tape, and held tight with plastic screws, but there WILL be some emi leakage
Yeah, we call this "transformer" and some guys use this to couple AC whilst isolating DC.
Bingo, that seems to be the magic keyword.
Yeah, why use a simple solution (two capacitors) if we can create a complicated one.
Yes, I think using just two capacitors would be the best solution.
Have to be careful how to choose them, to get best DC blocking performances at the working frequency.
ferrite beads are NOT a transformer. how could u think that?
Calm down. The OP asked about "ferrite bead transformer" in post #7 and only you misunderstood that.
Outer-DC-Block seems to be the term I need! Thank you.
Two capacitors would work but I was hoping for a screw-on adapter that was weather tight. I was also hoping it would be under S100.
At UHF frequencies transformers are made from ferrite beads all the time.
not sure where the heck you guys live, but around HERE, this is what you get when you ask for a ferrite bead:
http://www.digikey.com/product-detai...1-1-ND/1639565
or
http://www.digikey.com/product-detai...40-1-ND/806800
purely for making lossy lowpass filters
With something like this:
http://www.digikey.com/product-detai...38-1-ND/806798
you can pull out the heavy wire and wind 2 windings of smaller wire to get a transformer.