I'm Tired of turning Teflon to plasma (connector help)  - Page 1
Forum section: electronics / projects

author: qwaarjet
author_rank: Regular Contributor
timestamp: January 15, 2015, 04:53:03 am
content: Not really, plasma fun, just not in your equipment rackI have been using N type RF connector but have had the air breakdown few times in them now, this usably result in most of the Teflon turning to ash along with lots of scary sounds and smoke. My next set of experiments is going to push them right to the limit on peak voltage so I'm now more concerned with this issue. So Im looking for a 50ohm connector that can handle +3KV peak voltage and 10A DC and be somewhat affordable.

author: Vgkid
author_rank: Super Contributor
timestamp: January 15, 2015, 05:07:33 am
content: The only listed oneshttp://www.alliedelec.com/search/productdetail.aspx?SKU=70088907try these, look expensivehttp://www.fischerconnectors.com/sites/default/files/catalogues/core_series_catalog_chapter_7_en_1.0_mar10.pdfhttp://www.teledynereynolds.com/product/1singlepin/3-R75series/page12.asphttp://literature.hubersuhner.com/Technologies/Radiofrequency/RFConnectorsEN/?page=379

author: qwaarjet
author_rank: Regular Contributor
timestamp: January 15, 2015, 05:15:10 am
content: Thank the SHV/MHV don't have the current handling I need but the other look like they might work. Have to see how many first born I need to get them though.

author: Vgkid
author_rank: Super Contributor
timestamp: January 15, 2015, 05:54:49 am
content: That is the only issue I was running into was the current capacity. What frequency, and does it have to be coaxial.

author: qwaarjet
author_rank: Regular Contributor
timestamp: January 15, 2015, 06:39:23 am
content: The frequency is <50Mhz I would prefer coax to minimize stray RF from the HV pulses. Currently I have a piece of RG8 that is terminated in an N connector and N receptacle that is wired to two HV cable I twisted together and terminated with shrouded banana jacks it works but there is a lot of stray RF and I am at the voltage limits of the N connector. Keeping the coax is a big plus but not a complete show stopper. I really want the banana jacks out of the system and would just install an N connector but the chance of failure is very high at these voltages.

author: dave_k
author_rank: Frequent Contributor
timestamp: January 15, 2015, 07:00:34 am
content: 7-16 DIN connector might do the job...https://www.google.com.au/search?q=7-16+connector&source=lnms&tbm=isch&sa=X&ei=NGW3VKSXEcTQmwWF0oLADg&ved=0CAgQ_AUoAQ&biw=1280&bih=662

author: qwaarjet
author_rank: Regular Contributor
timestamp: January 15, 2015, 07:36:58 am
content: that seems like the way to go

author: LaserSteve
author_rank: Super Contributor
timestamp: January 15, 2015, 02:31:58 pm
content: Big RF based Plasma systems use a broadcast connector known as a "C" connector. Or they did 10 years ago when I maintained one.You can also look at the higher power Coax from Andrew with the matching connectors.Steve

author: Mr Simpleton
author_rank: Unknown
timestamp: January 15, 2015, 02:40:42 pm
content: C is somewhat more rugged than N and beeing bayonet locked. Sadly they are pretty much obsolete now, and even the military have given up on them.Sounds there is something strange going on when you kill the teflon in a N connector but your RG-8 cable survive... sounds like cheap chinese connectors??7/8 is for very high power but then often needs air filled cable too...

author: qwaarjet
author_rank: Regular Contributor
timestamp: January 15, 2015, 04:31:57 pm
content: Haven't had a problem with the cables yet, at least none not associated with the connector but have smoked numerous N and UHF connections. Normally the RF power is <500W but I'm also sending 3KV pulse down the same cable power isn't all that high power but at that voltage the air will break down and once that happens the DC bias (backed by a 2KW supply) on the line just eats the teflon.The connectors have all been purchased from major digikey or Allied so I doubt that quality is the problem.

author: Mr Simpleton
author_rank: Unknown
timestamp: January 15, 2015, 04:42:34 pm
content: Interesting stuff on wikipedia, a lot less ratings than I expected"Typical makers' curves for a new clean connector with a perfect load (VSWR=1.0) give limits of ?5000 W at 20 MHz and ?500 W at 2 GHz. This square root frequency derating law is expected from the skin depth decreasing with frequency. At lower frequencies the same maker recommends an upper bound of ?1000 V RMS. To achieve reliable operation in practice over an extended period, a safety factor of 5 or more is not uncommon, particularly when generic parts may be substituted, or the operating environment is likely to lead to eventual tarnishing of the contacts."