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SMBs to relieve torsion on coaxes

I'm building an extender for my scope. A problem I have is that the
coax is very stiff. When I flip the module over, the torsion gets
transmitted along the coax and it eventually snaps the pins right off
the connector.
Are there any connectors designed to allow the coax to turn while
maintaining decent signal integrity?
DC-50MHz, riding on 65VDC.
I'm thinking SMBs. This is a one-of personal thing, it doesn't need to
be great. If it snaps out once in a while, it's not a big deal.
Any clever ideas out there?
 
R

Rich Grise

Jan 1, 1970
0
I'm building an extender for my scope. A problem I have is that the
coax is very stiff. When I flip the module over, the torsion gets
transmitted along the coax and it eventually snaps the pins right off
the connector.
Are there any connectors designed to allow the coax to turn while
maintaining decent signal integrity?
DC-50MHz, riding on 65VDC.
I'm thinking SMBs. This is a one-of personal thing, it doesn't need to
be great. If it snaps out once in a while, it's not a big deal.
Any clever ideas out there?

BNC?

Good Luck!
Rich
 
J

John Larkin

Jan 1, 1970
0
I'm building an extender for my scope. A problem I have is that the
coax is very stiff. When I flip the module over, the torsion gets
transmitted along the coax and it eventually snaps the pins right off
the connector.
Are there any connectors designed to allow the coax to turn while
maintaining decent signal integrity?
DC-50MHz, riding on 65VDC.
I'm thinking SMBs. This is a one-of personal thing, it doesn't need to
be great. If it snaps out once in a while, it's not a big deal.
Any clever ideas out there?


MCX's are even turnier than SMB's, which can have a lot of retention
force. And there is tons of cheap MCX stuff on ebay.

John
 
S

Steve

Jan 1, 1970
0
I use Hirose x.FL connectors (Digikey). These are very small, good to
several GHz, and they latch very well. You can't really make your own
cables. I buy 12 inch cables and cut them in half to solder one end into RF
prototypes. For disconnect or production test, mount the cheap SMD female
recept on the circuit board. Hirose makes several sizes of this style
connector, but adapters might not be available for all of them. The SMA
adapter is the biggest expense, but they seem to last a long time. Hirose
sells a disconnect tool, but a strong fingernail will pop them apart. They
spin nicely, but the 12" cable will be so flexible I doubt it will matter.
Steve
 
J

john jardine

Jan 1, 1970
0
I'm building an extender for my scope. A problem I have is that the
coax is very stiff. When I flip the module over, the torsion gets
transmitted along the coax and it eventually snaps the pins right off
the connector.
Are there any connectors designed to allow the coax to turn while
maintaining decent signal integrity?
DC-50MHz, riding on 65VDC.
I'm thinking SMBs. This is a one-of personal thing, it doesn't need to
be great. If it snaps out once in a while, it's not a big deal.
Any clever ideas out there?

Dunno what the "very stiff" stuff may be but for test leads I use RG174u
coax. It's only 2.8mm and very flexible.
 
Dunno what the "very stiff" stuff may be but for test leads I use RG174u
coax. It's only 2.8mm and very flexible.

Plenum RG-62U that's been on a reel for 15 years. I need 93 ohm coax
so as not to load the tube drivers. Oh man the trouble I went through
to get that coax working. As plenum cable, the center conductor was
silver-plated steel. So I got some 22AWG silver-plated stranded wire.
I managed to strip the Teflon off lengthwise, solder it on the end of
the steel wire, and "fish" it through the 4 feet lengths of coax I
need.
Then I made another jig to score the very stiff outer jacket of the
coax. Every three inches I scored the circumference down to the braid.
Now I have flexible 93 ohm coax that tests very nice in the real
world. But it's still so torsionally stiff it snapped a pin off a
vintage Blue Ribbon connector.

I'm a bit anal because I calibrate the plug-ins outside the scope,
then when it's in the scope I don't want to have to tweak it because
the impedance of my cables was off.

The "real" extender has never shown up on eBay in the four years I've
looked.
 
J

john jardine

Jan 1, 1970
0
Plenum RG-62U that's been on a reel for 15 years. I need 93 ohm coax
so as not to load the tube drivers. Oh man the trouble I went through
to get that coax working. As plenum cable, the center conductor was
silver-plated steel. So I got some 22AWG silver-plated stranded wire.
I managed to strip the Teflon off lengthwise, solder it on the end of
the steel wire, and "fish" it through the 4 feet lengths of coax I
need.
Then I made another jig to score the very stiff outer jacket of the
coax. Every three inches I scored the circumference down to the braid.
Now I have flexible 93 ohm coax that tests very nice in the real
world. But it's still so torsionally stiff it snapped a pin off a
vintage Blue Ribbon connector.

I'm a bit anal because I calibrate the plug-ins outside the scope,
then when it's in the scope I don't want to have to tweak it because
the impedance of my cables was off.

The "real" extender has never shown up on eBay in the four years I've
looked.

You've the patience of 'Jobe' 'Job'? :)
If it's the 547 'scope, at 50MHz (i.e near DC!) would have thought the
cabling would be barely noticeable. But yes, I'm also loathe to let
something be if I know I can do something about it.
 
You've the patience of 'Jobe' 'Job'? :)

I'm crazy. I also need my 1S1 back in service.
If it's the 547 'scope, at 50MHz (i.e near DC!) would have thought the

Good guess, that's what it is. Nice scope in winter. Now that it's
getting warmer, not so much... :)
cabling would be barely noticeable. But yes, I'm also loathe to let
something be if I know I can do something about it.

Yeah it actually wasn't that hard to tweak the cables. I figure since
my braided 22AWG has the same O.D. as the steel, I stay pretty close
to 93 ohms, as long as I don't mush the dielectric too much out of
round.

It's really just a question of having the same results when I take the
extender off and jam the plug-in in the scope. Worked until the pin
snapped off.
 
J

joseph2k

Jan 1, 1970
0
Plenum RG-62U that's been on a reel for 15 years. I need 93 ohm coax
so as not to load the tube drivers. Oh man the trouble I went through
to get that coax working. As plenum cable, the center conductor was
silver-plated steel. So I got some 22AWG silver-plated stranded wire.
I managed to strip the Teflon off lengthwise, solder it on the end of
the steel wire, and "fish" it through the 4 feet lengths of coax I
need.
Then I made another jig to score the very stiff outer jacket of the
coax. Every three inches I scored the circumference down to the braid.
Now I have flexible 93 ohm coax that tests very nice in the real
world. But it's still so torsionally stiff it snapped a pin off a
vintage Blue Ribbon connector.

I'm a bit anal because I calibrate the plug-ins outside the scope,
then when it's in the scope I don't want to have to tweak it because
the impedance of my cables was off.

The "real" extender has never shown up on eBay in the four years I've
looked.
Since plenum conditions do not apply, just get some superflex class coax.
 
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