Co-axial connector, twin axial cable

SamR

Joined Mar 19, 2019
5,064
They used to be a common item for 75Ω twinax to the cable terminal on the back of TV sets. Probably have some hidden away in a junk box, BUT they are 75Ω as is twinax. Just what are you trying to connect at what impedance? Seems that now there is another kind of twinax than what I used to deal with as a HAM.
 

nsaspook

Joined Aug 27, 2009
13,446
They used to be a common item for 75Ω twinax to the cable terminal on the back of TV sets. Probably have some hidden away in a junk box, BUT they are 75Ω as is twinax. Just what are you trying to connect at what impedance? Seems that now there is another kind of twinax than what I used to deal with as a HAM.
We sometimes use twinax for charged particle faraday pickup connections.
1712600546203.png
1712600687910.png
TWBNC
https://www.milestek.com/p-16951-78-ohm-twinaxial-cable-0150-od
1712600603408.png
TWBNC to TRB triax adapter.

https://blog.pasternack.com/coax-co...d-other-coaxial-and-triaxial-connector-terms/
Deciphering TRB, TRT, TRS, TTM, TRC, TRN, TWBNC, TWTNC, Triax, Twinax, and other coaxial and triaxial connector terms

If you need an adapter, look there.
 

SamR

Joined Mar 19, 2019
5,064
@eetech00 I haven't seen that stuff in years but yes, it was basically a 300Ω to 75Ω (RG-59?) transformer. What we called twinax (plastic flat 2-wire antenna "cable") is not what they are now calling twinax for data transmission networks. That old stuff had no ground shield like a true coax. Just a cheap form of the very old Ladder-Wire for antennas.
 

nsaspook

Joined Aug 27, 2009
13,446
@eetech00 I haven't seen that stuff in years but yes, it was basically a 300Ω to 75Ω (RG-59?) transformer. What we called twinax (plastic flat 2-wire antenna "cable") is not what they are now calling twinax for data transmission networks. That old stuff had no ground shield like a true coax. Just a cheap form of the very old Ladder-Wire for antennas.
We never called the 300 ohm RF stuff 'twinax', we only called it 'twin lead' for twin wire lead-in cable.
https://en.wikipedia.org/wiki/Twin-lead

Transmitter cable.
1712613547709.png

Receiver cable
1712613584180.png

Shield pair twinax
1712613641959.png

Only a few antenna systems (fixed frequency VHF emergency radio systems) were still using ladder-lead feed systems when I was in, almost everything was HELIAX pressurized coax cables to antennas like this.

I just noticed that here on the video, they have what we called, the 'Coke Machine', it was TS/SCI rated secure voice switcher.
The RED equipment cabinet in the receiver technical control space.
 
Last edited:

eetech00

Joined Jun 8, 2013
4,017
@eetech00 I haven't seen that stuff in years but yes, it was basically a 300Ω to 75Ω (RG-59?) transformer. What we called twinax (plastic flat 2-wire antenna "cable") is not what they are now calling twinax for data transmission networks. That old stuff had no ground shield like a true coax. Just a cheap form of the very old Ladder-Wire for antennas.
The coupler I remember had a coax connector with a barrel type body containing a transformer. The twin-lead stuck out the other end with each wire terminated with spade terminal.
 

MisterBill2

Joined Jan 23, 2018
19,091
The Twinax cables that I am familiar with were for linking computers MANY LONG YEARS AGO. That stuff had a differential pair inside a single coaxial shield.We had hundreds of pounds of it and never found a decent use for it because of te strange connectors.
 

nsaspook

Joined Aug 27, 2009
13,446
The Twinax cables that I am familiar with were for linking computers MANY LONG YEARS AGO. That stuff had a differential pair inside a single coaxial shield.We had hundreds of pounds of it and never found a decent use for it because of te strange connectors.
We have some odd-ball Twinax connectors that I only see in some older cryogenic pumping networking systems today.
http://www.interfacebus.com/Design_1553_Twinax_Connector.html
1712625356473.png
https://www.belfuse.com/product/pro...rompeterCinchConnectivitySolutionsProductType
 

SamR

Joined Mar 19, 2019
5,064
I found this after a few minutes of rooting through the junk tubs. It's the opposite of what I was looking for. This is one used for TVs with screw terminals instead of a coax port to bring cable TV to screwed connections. Yeah, we also called it twin lead but around here ~45 years ago it was also being called twinax albeit probably improperly so. I looked around and found already terminated twinax cables but not the terminals alone.
1712629801301.png
 

MisterBill2

Joined Jan 23, 2018
19,091
The "Twinaxial" cable was never ever used for Television applications. It was a computer interface .
Twin LEAD is an entirely different animal still used for some varieties of antennas and connections. Totally different in every aspect.
 

Ya’akov

Joined Jan 27, 2019
9,250
The "Twinaxial" cable was never ever used for Television applications. It was a computer interface .
Twin LEAD is an entirely different animal still used for some varieties of antennas and connections. Totally different in every aspect.
Just a nitpick: Twinax has properties that makes it very useful for some applications that have nothing to do with computer networking. Any place high frequency differential signaling is needed twinax (shielded twisted pair) is a candidate. It is also used in connection of sensors, and interconnection of test gear in noisy environments.
 

MisterBill2

Joined Jan 23, 2018
19,091
Just a nitpick: Twinax has properties that makes it very useful for some applications that have nothing to do with computer networking. Any place high frequency differential signaling is needed twinax (shielded twisted pair) is a candidate. It is also used in connection of sensors, and interconnection of test gear in noisy environments.
My comment was primarily because it seemed that some confuse "Twinax cable" with TwinLEAD cable. Certainly very different .
 
Top