[R-390] DIY $10 Twinax to BNC adaptor

[Tom Norris]

With all the hoo-hah about the assorted adaptors out there such as  
the UG-970 from Fair and other sources, figured I'd mention how easy  
it would be to make your own.

I apologize for the quality of my writing, I've had a headache for  
some time and it won't seem to go away.

To make an adaptor I use a twinax connector and a BNC panel mount  
connector.
http://www.fernblatt.net/A/390_adaptor/   has a list of unorganized  
photos of
my cheapie special.

Twinax connectors are standard stock items in Mouser and many other  
electronic catalogs.
The Amphenol catalog number is 82-5589-RFX for the lowest priced  
version.  If you can't
find them, email me, I'll give you the phone number of my local  
distributor.

First collect all the parts of the twinax connector from the  
package.  Assembly should be fairly intuitive, if not there is an  
assembly diagram in the R-390/390A manuals.

First, one side of the twinax connector.  I do so in a way that  
provides some physical support for the grounded pin.   Locate a piece  
of tinned steel component lead, such as from a rectifier, or find a  
piece of of steel paper clip.  Drill a small hole as far down the  
body of the connector as possible on the same side of the pin to the  
grounded -- see the photos.  Solder wire to pin then route other end  
through hole in connector.  Solder.

Solder short piece of wire, preferably teflon-insulated to remaining  
pin, strip and trim wire slightly longer than body of connector,  
assemble outside screw-on ring of connector and set aside.

Next prepare the BNC connector.  Since I'm lazy, on the past couple  
of these I've ground the threads off the the back off the connector.  
Again, see photo of example.  Solder wire from previous step to  
center pin.  Fill inside of connector with hi-temp epoxy or silicone  
to hold the connector parts together, insert BNC into end of twinax  
connector and set aside until epoxy/silicone cures.  After this has  
cured solder the joint between BNC connector and twinax connector,  
using flux as needed.


This probably isn't the best way of building an adaptor -- I think  
some folks have threaded the inside of the twinax connectors to  
accept the BNC connector.

Other than the setting time for the glue, it only takes a few minutes  
to put together.  It's ugly.  It's cheap.  I've got several and no  
matter how quickly I've put one together they all still work.

Tom NU4G