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Author Topic:   Installing BNC Coax Connectors
prm1177 posted 10-05-2005 03:09 PM ET (US)   Profile for prm1177   Send Email to prm1177  
The installation of my Garmin supplemental antenna (for recieving satellite weather information) will require cutting off the BNC connector and then re-terminating it after pulling the antenna wire through the hard-top stanchion. Garmin "strongly" discourages this as they require a 0-dB loss connection.

Has anyone done this successfully? I can see problems with a crimp-on 50 Ohm BNC connector, but I plan to use a quality solder-on connector and then cover this with shrink tubing.

bsmotril posted 10-05-2005 09:42 PM ET (US)     Profile for bsmotril  Send Email to bsmotril     
I don't think there will be a problem if you can create a good solder joint, and use a connector with the same loss spec at the frequencies used by the weather receiver. The hardest part of the task will be pulling a single wire down through the stanchion, it's tough. I was never able to do it. I pulled the hole bundle down, added the new cable, then pulled the whole bundle back up through again. BillS
Chuck Tribolet posted 10-05-2005 11:51 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Dunno about the weather antenna, but I shortened my GPS
antenna cable, using one of the Shake Center-Pin BNC
connectors. Garmin had said it would work, but would void
the (already expired) warantee.

A good crimp-on BNC should work just as well as a solder-on,
at least until it gets wet.


jimh posted 10-06-2005 08:50 AM ET (US)     Profile for jimh  Send Email to jimh     
What frequency is involved?

As far as I can tell, one BNC connector is as good as another, assuming they are the same impedance. Just get a connector which is properly sized for the coaxial able being used; there are so many different sizes!

I don't think replacing the connector will be a problem. Garmin is probably assuming (and rightly so) that installation of a BNC connector is beyond the skill of most boaters. However, it sounds like you are familiar with these connectors and won't have a problem.

prm1177 posted 10-06-2005 02:37 PM ET (US)     Profile for prm1177  Send Email to prm1177     

I've got a pull line already in place. A little soap/water solution on the cable and I should be able to get the coax through the pack. That's what I did when I replaced the Raymarine GPS with the Garmin.


Not sure what frequency they use, but I suspect since it is an XM satellite service, the data is in the 2.3 GHz S band. That's about a 13 cm wavelength (I think).

BW23 posted 10-10-2005 04:33 PM ET (US)     Profile for BW23  Send Email to BW23     
Here is a link that details how specialized BNC crimpers are.

It's difficult to justify the cost for 1 or 2 crimps.
A local VHF radio repair shop might have something compatible.

Chuck Tribolet posted 10-10-2005 05:26 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Or if you have a buddy who's in IT in a shop that has had
IBM mainframes for a while, the old IBM 3270 display system
used BNC connectors. This was the standard dumb terminal
display system on mainframes from about 1975 to about 1990,
and there are still a fair number around. These IT
organizations probably still have the crimpers (good IT
people are serious packrats).


Riverwhaler posted 10-10-2005 06:58 PM ET (US)     Profile for Riverwhaler  Send Email to Riverwhaler     
Try a pro video shop or Radio Shack lots of video cable is routed with BNC connectors. Not all connectors fit all the cable sizes. You need to get connector for the cable you are using. RG58 is different from RG59. Tell me the cable type and I might be able to loan you a crimper if it is same as video types.
Chuck Tribolet posted 10-11-2005 02:01 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
It just sank in who was doing the original post and where
he works. No mainframes, but 10base2 Ethernet used BNC too,
and the IT folks may well still have a crimper around.

But as everbody keeps say, it's gotta match the cable.

Or, againm use the Shake CenterPin connectors.


prm1177 posted 10-12-2005 08:03 PM ET (US)     Profile for prm1177  Send Email to prm1177     

Whaddaya mean no mainframes? We still have some sgi 2000's linked together with Craylink! But you're right I guess. All we have now is the 2,500 processor server farm...

I'm leaning towards a solder, 50 Ohm connection. Crimping might be good enough, but I've seen crimps on video that can show impedance problems when you do a frequency sweep on them.

Chuck Tribolet posted 10-12-2005 11:34 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Are SGI 2000's water cooled?

No H2O, not mainframe. ;-)

BTW, new job assignment has me running Linux on real


jimh posted 10-13-2005 05:14 AM ET (US)     Profile for jimh  Send Email to jimh     
If the receiver system is operating at 2.3 GHz, it probably has a down-converter in the antenna. At that frequency, you can't get very far on small diameter coax. The system is probably operating around 75-MHz (a popular intermediate-frequency or IF) on the feedline you are installing the connector.

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