Need help finding connectors for RG-331 coax

bbo14

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Jul 29, 2018
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Hobbs, NM
I have about 300 feet of RG-331 coax, (low loss, 100% shielded, direct burial capable) that I got from a SK estate.

I need to find connectors, preferably adapters to SO-239, or N connector.

I have called several cable manufacturers with no results.

Can anyone recommend a source? Or do any of you have any connectors that are compatible?

I have measured the dimensions of the outer jacket, outer conductor, dialectric material and the center conductor in an attempt to find a connector that way with no results either.

I wonder if perhaps I need to be looking at connectors for the LMR series of cables? Perhaps LMR-600 or LMR-900?

Or does anyone have an alternative suggestion so I can use this to run out to my all-band HF vertical 250 feet away from my house?

I'm open to suggestions. Thanks for reading.

73, Bob
 

prcguy

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Connectors are probably out there but they seem to be very elusive. Since its for HF you could make a connector interface that holds a chassis mount SO-239. Maybe a thin sheet of aluminum sheet metal about an inch wide and 2 inches long with an SO-239 mounted on one end, then hose clamp the other end to the outside of the aluminum jacket and use some small tubular braid to solder over the coax center conductor and bridge to the SO-239 center pin. You could make it so the center conductor with braid is only a half inch long and it should be fine through maybe 6m.

Or if you could get fancy and get some thin wall tubing that just slides over the outer aluminum jacket, use some aluminum solder and put an end cap on it then install an SO-239 on the end of that. You would also slit the end opposite the connector so a hose clamp would tighten it onto the coax shield.

You would use a similar tubular braid over the coax center conductor to the SO-239 since they are much different OD and you could leave the SO-239 loose so the contraption with the end cap could slide way up onto the coax exposing the center conductor so you can solder the braid and SO-239 on, then if the holes for the SO-239 flange were tapped you could then slide the end cap thing out to straighten the braid and suck the end cap up against the SO-239 then tighten a hose clamp around the end cap thing to finish of the ground connection.

Might be hard to picture all this but I have a clear color picture in my head and could probably whip one together in an hour or less.


I have about 300 feet of RG-331 coax, (low loss, 100% shielded, direct burial capable) that I got from a SK estate.

I need to find connectors, preferably adapters to SO-239, or N connector.

I have called several cable manufacturers with no results.

Can anyone recommend a source? Or do any of you have any connectors that are compatible?

I have measured the dimensions of the outer jacket, outer conductor, dialectric material and the center conductor in an attempt to find a connector that way with no results either.

I wonder if perhaps I need to be looking at connectors for the LMR series of cables? Perhaps LMR-600 or LMR-900?

Or does anyone have an alternative suggestion so I can use this to run out to my all-band HF vertical 250 feet away from my house?

I'm open to suggestions. Thanks for reading.

73, Bob
 
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K4EET

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bbo14

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Jul 29, 2018
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Hobbs, NM
PRCGuy, thanks for the construction idea. I thought about that, using a 100% shielded box and gradually reducing both conductors down to the size required by the SO-239s since the impedance is determined by the ratio of the diameters of the inner vs. the outer conductor.

K4EET, I tried Allied tech support, but didn't have the MILSPEC equivalent number so now that i do, I'll call back to see what they can tell me. Also, you first said 331, but then said 311. It is 331. Probably the lateness of the hour. It's 11:20 PM here so I certainly understand, HI.

Thanks to both of you. i will call Allied Monday. In the meantime, I may sneak out to the shack tomorrow and try PRCGuy's adapter fabrication technique. I looked inside his head from afar and found out exactly what he was thinking about! (Or am I hallucinating? At this late hour, who knows?). 73 to both of you!
 

bbo14

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Oh, PRCGuy: I forgot to add, there is NO braid in RG-331. The outer conductor is solid aluminum 100% shielded. So it's a matter of making an ever-smaller center conductor and then an ever smaller outer conductor to fit inside the box to try to keep the impedance the same. (Obviously since the box needs to be shielded, it needs to be metal of some kind. 73, Bob
 

prcguy

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Yes, I know the shield is an aluminum tube. I would use a tubular braid from small coax like RG-58 to solder over maybe 1/4" to 3/8" of the center conductor sticking out and use that to bridge to the SO-239 center pin. Quickly tin the copper coating on the center conductor first, then slide the braid over then solder the braid. You will need a really big soldering gun as the center conductor is large and aluminum with copper clad over it.

You can hose clamp things to the outer aluminum tube for grounding. You could even put an SO-239 on a small box, cut a hole in the box to slide it over the aluminum outer shield, attach 3 or 4 small L brackets to the box so they lay against the coax shield tube then use a hose clamp to secure everything. Seems like I recommend a hose clamp for just about everything.

For HF frequencies lead lengths of 1/2" are nothing to worry about. You don't really need a shield box at HF but if you use one and do it right you could make a connection good through VHF or UHF.

Oh, PRCGuy: I forgot to add, there is NO braid in RG-331. The outer conductor is solid aluminum 100% shielded. So it's a matter of making an ever-smaller center conductor and then an ever smaller outer conductor to fit inside the box to try to keep the impedance the same. (Obviously since the box needs to be shielded, it needs to be metal of some kind. 73, Bob
 

bbo14

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Aluminum coax .600 outside diameter solid . AKA 'hard line". Maybe Talley.com
Oh gee, I forgot about Talley. If Allied can't come up with something I will call them. I also found out the dialectric is just a bit too large for insertion into a standard PL-259. However, if I drill out the threads inside the connector, I think it will fit. Then It's just a matter of "necking down" the center conductor and closing the seam between the end of the outer conductor and the end of the PL-259. Thanks to all for the ideas. It tickled the brain cells into activity again.
 

K4RBT

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May 12, 2011
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At the main site on Poor mountain, all of the original cable had the solid aluminum jacket, no outer jacket anb someone told me they got new connectors from Celwave. The connector required special trimming, chamfer on the center conductor and a square cut of the dielectric and aluminum tube. the clamping was done by groves cut one the inside of four fingers, You slid the front part on to the cable, then screwed the back shell on not letting the front rotate. This caused the fingers to bite in the aluminum. Vhf was ok, microwave had loss. All of it was scraped when a new tower was installed. Should have grabbed one for memory's sake. Isn't hindsight great!
 

bbo14

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Jul 29, 2018
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Hobbs, NM
Yeah, mine is 20 20 some days, 20 10 others. I think I have come up with a solution however. But thanks to you and all the others who replied. 73, Bob
 
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