For the Cable Guys: Coax cable Splitter Q.
 

Coaxial cable 2-way splitter: Should there be continuity between the
two leads (between the center electrode and the outer sheathing with
the threaded connectors)?

I have three of these splitters, two are brand new (Ideal 1GHz 2-Way
Cable TV Splitter; coax connection; one in, two out) and one is used,
unknown brand. Tested with a Triplett 2030-A tester. All 3 show
continuity, at negligibly small resistance, between the two leads.

I've tested the splitters with the cables attached and without cables
attached (only a copper pin to connect to the supposedly shielded
center). In all cases continuity exists between both leads.

I also tested the coaxial cables, with the crimped ends. All test
normal, i.e. - continuity throughout each lead, at both ends, but not
between the leads. This isolates the splitters, but am I interpreting
things correctly?

My natural instinct is that there should be continuity at both ends of
each connection, but _not between_ them. But then, what do I know. So,
for any cable guys, out the do I have three bad splitters, three
good spliters? What am I missing?

I'm 99% sure that these splitters are either bad or you are accidentally
shorting the shielding when making the tests. The outer shield is that, a
shield which should be connected to ground. If there is continuity between
the lead and the shield, you would be shorting out the signal to ground.

Jeff

"Michael Stoic" wrote in message
...
Coaxial cable 2-way splitter: Should there be continuity between the
two leads (between the center electrode and the outer sheathing with
the threaded connectors)?

I have three of these splitters, two are brand new (Ideal 1GHz 2-Way
Cable TV Splitter; coax connection; one in, two out) and one is used,
unknown brand. Tested with a Triplett 2030-A tester. All 3 show
continuity, at negligibly small resistance, between the two leads.

I've tested the splitters with the cables attached and without cables
attached (only a copper pin to connect to the supposedly shielded
center). In all cases continuity exists between both leads.

I also tested the coaxial cables, with the crimped ends. All test
normal, i.e. - continuity throughout each lead, at both ends, but not
between the leads. This isolates the splitters, but am I interpreting
things correctly?

My natural instinct is that there should be continuity at both ends of
each connection, but _not between_ them. But then, what do I know. So,
for any cable guys, out the do I have three bad splitters, three
good spliters? What am I missing?

You are looking at the windings of impedance matching transformers. TYou can't
trust a DC meter, at 100 meghertz they look like 75 ohms, just like the cable.

"Jeff Prevett" wrote:

I'm 99% sure that these splitters are either bad or you are accidentally
shorting the shielding when making the tests. The outer shield is that, a
shield which should be connected to ground. If there is continuity between
the lead and the shield, you would be shorting out the signal to ground.

It's only a short at DC, which is what your meter is measuring. These
devices are essentially transformers, and at RF, the inductance of the
windings provides the proper impedance matching. (Assuming all the
ports are properly terminated.)

In short, the OP's measurements are exactly what would be expected. At
DC, there should be continuity between all four terminals of a two way
splitter. (It, Out2, Out2, shield/case.) It looks something like this:

(------ Out 1
In ---) (
) (---+-- Shield
) |
) (------ Out 2
Shield -+-) ( |
| (---+-- Shield
\--Case-+

(Note, it may not be clear, but the shield side of each winding is
connected to the case, and as such, they are all tied together.)

To the OP: Do you have a specific problem with your equipment, or are
you just measuring for fun?

Michael Stoic wrote:
Coaxial cable 2-way splitter: Should there be continuity between the
two leads (between the center electrode and the outer sheathing with
the threaded connectors)?

I have three of these splitters, two are brand new (Ideal 1GHz 2-Way
Cable TV Splitter; coax connection; one in, two out) and one is used,
unknown brand. Tested with a Triplett 2030-A tester. All 3 show
continuity, at negligibly small resistance, between the two leads.

I've tested the splitters with the cables attached and without cables
attached (only a copper pin to connect to the supposedly shielded
center). In all cases continuity exists between both leads.

I also tested the coaxial cables, with the crimped ends. All test
normal, i.e. - continuity throughout each lead, at both ends, but not
between the leads. This isolates the splitters, but am I interpreting
things correctly?

My natural instinct is that there should be continuity at both ends of
each connection, but _not between_ them. But then, what do I know. So,
for any cable guys, out the do I have three bad splitters, three
good spliters? What am I missing?
Hi,
You are looking at transformer coupled stuff. No continuity with meter.
Toroidal core and windings. RF energy is split/transfered by tiny
tranformer.
Tony

Longtime Lurker wrote:
"Jeff Prevett" wrote:


I'm 99% sure that these splitters are either bad or you are accidentally
shorting the shielding when making the tests. The outer shield is that, a
shield which should be connected to ground. If there is continuity between
the lead and the shield, you would be shorting out the signal to ground.


It's only a short at DC, which is what your meter is measuring. These
devices are essentially transformers, and at RF, the inductance of the
windings provides the proper impedance matching. (Assuming all the
ports are properly terminated.)

In short, the OP's measurements are exactly what would be expected. At
DC, there should be continuity between all four terminals of a two way
splitter. (It, Out2, Out2, shield/case.) It looks something like this:

(------ Out 1
In ---) (
) (---+-- Shield
) |
) (------ Out 2
Shield -+-) ( |
| (---+-- Shield
\--Case-+

(Note, it may not be clear, but the shield side of each winding is
connected to the case, and as such, they are all tied together.)

To the OP: Do you have a specific problem with your equipment, or are
you just measuring for fun?


Yup, that's why coax is called unbalanced line.
Tony

To the OP: Do you have a specific problem with your equipment, or are
you just measuring for fun?

I measured for the sake of double cheching the assembly before it is
inside the wall.

MS







On Mon, 17 Jan 2005 04:33:04 GMT, (Longtime Lurker)
wrote:

"Jeff Prevett" wrote:

I'm 99% sure that these splitters are either bad or you are accidentally
shorting the shielding when making the tests. The outer shield is that, a
shield which should be connected to ground. If there is continuity between
the lead and the shield, you would be shorting out the signal to ground.

It's only a short at DC, which is what your meter is measuring. These
devices are essentially transformers, and at RF, the inductance of the
windings provides the proper impedance matching. (Assuming all the
ports are properly terminated.)

In short, the OP's measurements are exactly what would be expected. At
DC, there should be continuity between all four terminals of a two way
splitter. (It, Out2, Out2, shield/case.) It looks something like this:

(------ Out 1
In ---) (
) (---+-- Shield
) |
) (------ Out 2
Shield -+-) ( |
| (---+-- Shield
\--Case-+

(Note, it may not be clear, but the shield side of each winding is
connected to the case, and as such, they are all tied together.)