Twinax coax connectors

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delco1946
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316
Jan Thu 01, 1970 12:00 am
Gladstone, Oregon

Twinax coax connectors

Post by delco1946 »

Just bought about 40 feet of twinax cable for a good deal, which was pretty exciting. However, now I need to make connections and not finding a lot of options and I’ve never done this. What tools would I need for crimping the coax shield to a connector? Any recommended suppliers? Thanks!
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stevebyan
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May Wed 18, 2011 1:40 am
Littleton, MA
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Re: Twinax coax connectors

Post by stevebyan »

If I recall correctly, the twin ax connectors I’ve used are similar to the clamp-style N connector or BNC connector. The shield is clamped between a nut and the shell of the connector. No crimping involved.

https://www.mouser.com/datasheet/2/18/1 ... 326025.pdf" -="window.open(this.href);return false;

What style of connector are you contemplating? UG-421 or something else?

Philmore has the UG-421 style:
http://www.philmore-datak.com/mc/Page%2050.pdf" -="window.open(this.href);return false;
delco1946
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Jan Thu 01, 1970 12:00 am
Gladstone, Oregon

Re: Twinax coax connectors

Post by delco1946 »

That’s the type I’m finding tonight, too, which I think would work. I’m planning to use this as feeder wire for a balanced dipole/ doublet antenna. The top end it might be easiest to strip and solder wires directly to the antenna wires unless I can find some homemade connector to do this. The bottom end I’m thinking of having some sort of connector with splitters to various radios and my radio bench.

Those links are quite helpful to see some connector options. I was having a hard time finding examples.
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Barry H Bennett
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Nov Wed 30, 2016 6:35 pm
Sunbury, Ohio 43074
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Re: Twinax coax connectors

Post by Barry H Bennett »

You will have to find a crimp tool that has dies for the exact dimensions of the connectors and cable you are using. While you could, theoretically, use a "generic" hand crimp tool for this, your connections are going to be less than the best they can be unless crimped with the proper die.
Preserving the hist. of electronics, one boat anchor at a time! :)
https://www.bbtvtestequipment.com
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stevebyan
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May Wed 18, 2011 1:40 am
Littleton, MA
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Re: Twinax coax connectors

Post by stevebyan »

You’ll need some kind of strain relief at the top. You could fashion one out of a small plate of 1/4 inch Lexan. Drill some mounting holes through it and zip-tie your cable to the plate.
jim rozen
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Mar Wed 16, 2011 9:44 pm
Peekskill, NY 10566

Re: Twinax coax connectors

Post by jim rozen »

Twinax cable cqn be terminated with TBNC (twin BNC - two center pins offset from each other) o, as best practice, using triax connectors. Trompeter electronics who specialized in this has gone out of business but other conmpanies make similar products.

https://www.pasternack.com/nsearch.aspx ... _type=grid" -="window.open(this.href);return false;
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Chas
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Jan Thu 01, 1970 12:00 am
S. Dartmouth MA USA

Re: Twinax coax connectors

Post by Chas »

The top end it might be easiest to strip and solder wires directly to the antenna wires unless I can find some homemade connector to do this.
Avoid having open stripped ends of the cable exposed to the weather. Even with connectors, outdoors, be sure they are weather protected. Once the cable wicks in moisture it will be ruined.

I, would use a switching method rather than a splitter as there is initial insertion loss and 3 db to each port of an un-amplified device.

If the cable is not matched at the receiver end losses will rise, the cable will become a shunting capacitor. Signal gained at the dipole termination will be attenuated by the cable.

YMMV

Chas

WA1JFD
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KX5JSC
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Dec Sat 28, 2019 3:18 pm
Corinth, TX, USA

Re: Twinax coax connectors

Post by KX5JSC »

Weather shield as best you can. Even then, mount it upside-down using a drip shield.

John
delco1946
Member
316
Jan Thu 01, 1970 12:00 am
Gladstone, Oregon

Re: Twinax coax connectors

Post by delco1946 »

wowsers that pasternick site is pricey! :shock:

Chas - response in bold:
1) Avoid having open stripped ends of the cable exposed to the weather. Even with connectors, outdoors, be sure they are weather protected. Once the cable wicks in moisture it will be ruined. Understood

I, would use a switching method rather than a splitter as there is initial insertion loss and 3 db to each port of an un-amplified device. I think I follow. How do you recommended I switch between twinax lines? Is there some sort of device for this or are you saying to unscrew one connecting twinax line that runs off to one set, for a different twinax running off to another set?

If the cable is not matched at the receiver end losses will rise, the cable will become a shunting capacitor. Signal gained at the dipole termination will be attenuated by the cable. The twinax is 100 ohms which should be close to the 75-100 ohms that vintage sets seem to be design for, correct? I specifically avoided ladder line (450 ohms) which didn't exist in the 30s and 40s and stuck to what i'll call "twisted wire technology" which is what was used during this era (with the thinking that the radios would be inherently designed for impedance expected). I'm building this antenna for old radios that have two antenna wire connections already in place which i have presumed means they are designed for 75-100 ohms impedance antenna wire. Does that rationale check out?

Thanks
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Chas
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Jan Thu 01, 1970 12:00 am
S. Dartmouth MA USA

Re: Twinax coax connectors

Post by Chas »

Is there some sort of device for this or are you saying to unscrew one connecting twinax line that runs off to one set, for a different twin-ax running off to another set?
There probably is, but if connectors as so pricey except the same for a rotary witch.

I have made perfectly adequate rotary RF switches using electricians hexagonal mud work metal boxes and covers. It was for UHF connectors and I bought a number of bulkhead nut fastened connectors from a Florida surplus vendor.

https://www.mpja.com/UHF-Connectors/products/92/" -="window.open(this.href);return false;

The twin-ax impedance is "close enough" for receiving.

FYI As for open wire, early hams (20's & later) made open wire line up to 1800 ohms. Twisted pair was very popular for 75 ohm impedance and power cord was often used for this purpose.

It won't matter to any extent if coax is used for a radio that is expecting a twisted pair. Many radios advised an alternate of ground one side or the other of a balance input if it improved reception.

You can always convert to 75 ohm coax, inside, even if connectors are not used by fabricating running splices, then , conventional UHF (cheap) connectors can be used.

GL

Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
delco1946
Member
316
Jan Thu 01, 1970 12:00 am
Gladstone, Oregon

Re: Twinax coax connectors

Post by delco1946 »

Doesn't look like anything in that link supports twinax. I'll just switch between sets as i described i guess.

I'm using the twinax as it is basically twisted wire - 2 conductors inside a shield so hopefully will avoid the interference pitfalls of (unshielded) twisted wire while also avoiding the unbalanced nature of single conductor coax.

Fingers crossed it works as will as i hope!
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