Discussion:
Dressing RG6
(too old to reply)
Don Y
2024-05-14 16:51:38 UTC
Permalink
I've several short (a few feet) lengths of RG6 that I
would like to "strongly coerce" into assuming a particular
dressing.

Securing the cables to a stationary surface isn't practical
without significantly lengthening them and distorting
their "natural" routing.

But, ISTM that I should be able to slip each cable into
a comparable diameter copper (?) pipe and then use traditional
tools to bend that pipe into the appropriate configuration.
I'd have to observe constraints like minimum bend radius
but are there other issues that I might "discover" down the
road?
Phil Hobbs
2024-05-14 17:18:49 UTC
Permalink
Post by Don Y
I've several short (a few feet) lengths of RG6 that I
would like to "strongly coerce" into assuming a particular
dressing.
Securing the cables to a stationary surface isn't practical
without significantly lengthening them and distorting
their "natural" routing.
But, ISTM that I should be able to slip each cable into
a comparable diameter copper (?) pipe and then use traditional
tools to bend that pipe into the appropriate configuration.
I'd have to observe constraints like minimum bend radius
but are there other issues that I might "discover" down the
road?
You’re planning to make a random- length shotgun balun.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
Phil Hobbs
2024-05-14 18:27:08 UTC
Permalink
Post by Phil Hobbs
Post by Don Y
I've several short (a few feet) lengths of RG6 that I
would like to "strongly coerce" into assuming a particular
dressing.
Securing the cables to a stationary surface isn't practical
without significantly lengthening them and distorting
their "natural" routing.
But, ISTM that I should be able to slip each cable into
a comparable diameter copper (?) pipe and then use traditional
tools to bend that pipe into the appropriate configuration.
I'd have to observe constraints like minimum bend radius
but are there other issues that I might "discover" down the
road?
You’re planning to make a random- length shotgun balun.
Cheers
Phil Hobbs
Bazooka balun.
--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
Don
2024-05-14 19:22:12 UTC
Permalink
Post by Phil Hobbs
Post by Phil Hobbs
Post by Don Y
I've several short (a few feet) lengths of RG6 that I
would like to "strongly coerce" into assuming a particular
dressing.
Securing the cables to a stationary surface isn't practical
without significantly lengthening them and distorting
their "natural" routing.
But, ISTM that I should be able to slip each cable into
a comparable diameter copper (?) pipe and then use traditional
tools to bend that pipe into the appropriate configuration.
I'd have to observe constraints like minimum bend radius
but are there other issues that I might "discover" down the
road?
You’re planning to make a random- length shotgun balun.
Bazooka balun.
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.

Danke,
--
Don, KB7RPU, https://www.qsl.net/kb7rpu
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.
John Larkin
2024-05-14 20:13:32 UTC
Permalink
Post by Don
Post by Phil Hobbs
Post by Don Y
I've several short (a few feet) lengths of RG6 that I
would like to "strongly coerce" into assuming a particular
dressing.
Securing the cables to a stationary surface isn't practical
without significantly lengthening them and distorting
their "natural" routing.
But, ISTM that I should be able to slip each cable into
a comparable diameter copper (?) pipe and then use traditional
tools to bend that pipe into the appropriate configuration.
I'd have to observe constraints like minimum bend radius
but are there other issues that I might "discover" down the
road?
You’re planning to make a random- length shotgun balun.
Bazooka balun.
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Danke,
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
Phil Hobbs
2024-05-14 21:46:35 UTC
Permalink
Post by John Larkin
Post by Don
Post by Phil Hobbs
Post by Don Y
I've several short (a few feet) lengths of RG6 that I
would like to "strongly coerce" into assuming a particular
dressing.
Securing the cables to a stationary surface isn't practical
without significantly lengthening them and distorting
their "natural" routing.
But, ISTM that I should be able to slip each cable into
a comparable diameter copper (?) pipe and then use traditional
tools to bend that pipe into the appropriate configuration.
I'd have to observe constraints like minimum bend radius
but are there other issues that I might "discover" down the
road?
You’re planning to make a random- length shotgun balun.
Bazooka balun.
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Danke,
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.

Depending on the application, you may or may not care.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
Jeroen Belleman
2024-05-14 22:08:26 UTC
Permalink
Post by Phil Hobbs
Post by John Larkin
Post by Don
Post by Phil Hobbs
Post by Don Y
I've several short (a few feet) lengths of RG6 that I
would like to "strongly coerce" into assuming a particular
dressing.
Securing the cables to a stationary surface isn't practical
without significantly lengthening them and distorting
their "natural" routing.
But, ISTM that I should be able to slip each cable into
a comparable diameter copper (?) pipe and then use traditional
tools to bend that pipe into the appropriate configuration.
I'd have to observe constraints like minimum bend radius
but are there other issues that I might "discover" down the
road?
You’re planning to make a random- length shotgun balun.
Bazooka balun.
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Danke,
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
Cheers
Phil Hobbs
I've been putting coax inside copper tubes or braids to measure
and/or reduce the transfer impedance (leakage). I did that to
measure small signals in a particle accelerator, which typically
has kicker magnets and RF cavities with kA currents and kV
voltages nearby.

A colleague developed a special low transfer impedance coax
cable for this sort of application. It had two screens with
intermediate magnetic shielding. It was unpleasant to work
with, because part of the magnetic shielding was a steel
spiral foil tape that was razor sharp. But it worked really
well.

Jeroen Belleman
Don
2024-05-14 23:33:35 UTC
Permalink
<snip>
Post by Jeroen Belleman
Post by Phil Hobbs
Post by John Larkin
Post by Don
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
I've been putting coax inside copper tubes or braids to measure
and/or reduce the transfer impedance (leakage). I did that to
measure small signals in a particle accelerator, which typically
has kicker magnets and RF cavities with kA currents and kV
voltages nearby.
A colleague developed a special low transfer impedance coax
cable for this sort of application. It had two screens with
intermediate magnetic shielding. It was unpleasant to work
with, because part of the magnetic shielding was a steel
spiral foil tape that was razor sharp. But it worked really
well.
Empirical observation always trumps theory for me. Did you ground [1]
the copper tubes or braids?

Note.

[1] Whitlock cynicism can be ignored:

Q. What does "ground" mean?
A. A fantasy invented by engineers to simplify their work.

_An Overview of Audio System Grounding & Interfacing_
by Bill Whitlock

Danke,
--
Don, KB7RPU, https://www.qsl.net/kb7rpu
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.
John Larkin
2024-05-15 00:31:17 UTC
Permalink
Post by Don
<snip>
Post by Jeroen Belleman
Post by John Larkin
Post by Don
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
I've been putting coax inside copper tubes or braids to measure
and/or reduce the transfer impedance (leakage). I did that to
measure small signals in a particle accelerator, which typically
has kicker magnets and RF cavities with kA currents and kV
voltages nearby.
A colleague developed a special low transfer impedance coax
cable for this sort of application. It had two screens with
intermediate magnetic shielding. It was unpleasant to work
with, because part of the magnetic shielding was a steel
spiral foil tape that was razor sharp. But it worked really
well.
Empirical observation always trumps theory for me. Did you ground [1]
the copper tubes or braids?
Note.
Q. What does "ground" mean?
A. A fantasy invented by engineers to simplify their work.
_An Overview of Audio System Grounding & Interfacing_
by Bill Whitlock
Danke,
I means just what it says. Dirt.
Jeroen Belleman
2024-05-15 09:03:22 UTC
Permalink
Post by Don
<snip>
Post by Jeroen Belleman
Post by Phil Hobbs
Post by John Larkin
Post by Don
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
I've been putting coax inside copper tubes or braids to measure
and/or reduce the transfer impedance (leakage). I did that to
measure small signals in a particle accelerator, which typically
has kicker magnets and RF cavities with kA currents and kV
voltages nearby.
A colleague developed a special low transfer impedance coax
cable for this sort of application. It had two screens with
intermediate magnetic shielding. It was unpleasant to work
with, because part of the magnetic shielding was a steel
spiral foil tape that was razor sharp. But it worked really
well.
Empirical observation always trumps theory for me. Did you ground [1]
the copper tubes or braids?
Both ends were connected to the connector shields. The point of
the exercise was to reduce transfer impedance, which at low
frequency (<1MHz) is simply proportional to screen resistance.

Jeroen Belleman
John Larkin
2024-05-15 14:27:07 UTC
Permalink
On Wed, 15 May 2024 11:03:22 +0200, Jeroen Belleman
Post by Jeroen Belleman
Post by Don
<snip>
Post by Jeroen Belleman
Post by John Larkin
Post by Don
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
I've been putting coax inside copper tubes or braids to measure
and/or reduce the transfer impedance (leakage). I did that to
measure small signals in a particle accelerator, which typically
has kicker magnets and RF cavities with kA currents and kV
voltages nearby.
A colleague developed a special low transfer impedance coax
cable for this sort of application. It had two screens with
intermediate magnetic shielding. It was unpleasant to work
with, because part of the magnetic shielding was a steel
spiral foil tape that was razor sharp. But it worked really
well.
Empirical observation always trumps theory for me. Did you ground [1]
the copper tubes or braids?
Both ends were connected to the connector shields. The point of
the exercise was to reduce transfer impedance, which at low
frequency (<1MHz) is simply proportional to screen resistance.
Jeroen Belleman
Two parallel coaxes can make an attenuator.

What was the coupled frequency response like?
John Larkin
2024-05-15 15:06:03 UTC
Permalink
On Wed, 15 May 2024 07:27:07 -0700, John Larkin
Post by John Larkin
On Wed, 15 May 2024 11:03:22 +0200, Jeroen Belleman
Post by Jeroen Belleman
Post by Don
<snip>
Post by Jeroen Belleman
Post by John Larkin
Post by Don
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
I've been putting coax inside copper tubes or braids to measure
and/or reduce the transfer impedance (leakage). I did that to
measure small signals in a particle accelerator, which typically
has kicker magnets and RF cavities with kA currents and kV
voltages nearby.
A colleague developed a special low transfer impedance coax
cable for this sort of application. It had two screens with
intermediate magnetic shielding. It was unpleasant to work
with, because part of the magnetic shielding was a steel
spiral foil tape that was razor sharp. But it worked really
well.
Empirical observation always trumps theory for me. Did you ground [1]
the copper tubes or braids?
Both ends were connected to the connector shields. The point of
the exercise was to reduce transfer impedance, which at low
frequency (<1MHz) is simply proportional to screen resistance.
Jeroen Belleman
Two parallel coaxes can make an attenuator.
What was the coupled frequency response like?
Just say your data below.
Jeroen Belleman
2024-05-15 21:24:28 UTC
Permalink
Post by John Larkin
On Wed, 15 May 2024 07:27:07 -0700, John Larkin
Post by John Larkin
On Wed, 15 May 2024 11:03:22 +0200, Jeroen Belleman
Post by Jeroen Belleman
Post by Don
<snip>
Post by Jeroen Belleman
Post by Phil Hobbs
Post by John Larkin
Post by Don
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
I've been putting coax inside copper tubes or braids to measure
and/or reduce the transfer impedance (leakage). I did that to
measure small signals in a particle accelerator, which typically
has kicker magnets and RF cavities with kA currents and kV
voltages nearby.
A colleague developed a special low transfer impedance coax
cable for this sort of application. It had two screens with
intermediate magnetic shielding. It was unpleasant to work
with, because part of the magnetic shielding was a steel
spiral foil tape that was razor sharp. But it worked really
well.
Empirical observation always trumps theory for me. Did you ground [1]
the copper tubes or braids?
Both ends were connected to the connector shields. The point of
the exercise was to reduce transfer impedance, which at low
frequency (<1MHz) is simply proportional to screen resistance.
Jeroen Belleman
Two parallel coaxes can make an attenuator.
What was the coupled frequency response like?
Just say your data below.
I didn't?

Jeroen Belleman
Jeroen Belleman
2024-05-15 21:25:21 UTC
Permalink
Post by John Larkin
On Wed, 15 May 2024 11:03:22 +0200, Jeroen Belleman
Post by Jeroen Belleman
Post by Don
<snip>
Post by Jeroen Belleman
Post by Phil Hobbs
Post by John Larkin
Post by Don
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
I've been putting coax inside copper tubes or braids to measure
and/or reduce the transfer impedance (leakage). I did that to
measure small signals in a particle accelerator, which typically
has kicker magnets and RF cavities with kA currents and kV
voltages nearby.
A colleague developed a special low transfer impedance coax
cable for this sort of application. It had two screens with
intermediate magnetic shielding. It was unpleasant to work
with, because part of the magnetic shielding was a steel
spiral foil tape that was razor sharp. But it worked really
well.
Empirical observation always trumps theory for me. Did you ground [1]
the copper tubes or braids?
Both ends were connected to the connector shields. The point of
the exercise was to reduce transfer impedance, which at low
frequency (<1MHz) is simply proportional to screen resistance.
Jeroen Belleman
Two parallel coaxes can make an attenuator.
What was the coupled frequency response like?
Ah sorry, this message didn't seem to get sent...

At low frequency, the transfer ratio was simply the ratio
of screen resistance over characteristic impedance. At medium
frequencies, a few octaves roughly around 1MHz, there was a dip,
and above that a steady rise of about 10dB/decade.

Not all cables behaved the same. RG58 is poorly screened and
doesn't have the dip. UT141 had a very deep dip.

Details at
<https://jeroen.web.cern.ch/jeroen/coaxleakage/leakage.shtml>.

Jeroen Belleman
Phil Hobbs
2024-05-16 15:41:19 UTC
Permalink
Post by Jeroen Belleman
Post by John Larkin
On Wed, 15 May 2024 11:03:22 +0200, Jeroen Belleman
Post by Jeroen Belleman
Post by Don
<snip>
Post by Jeroen Belleman
Post by Phil Hobbs
Post by John Larkin
Post by Don
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
I've been putting coax inside copper tubes or braids to measure
and/or reduce the transfer impedance (leakage). I did that to
measure small signals in a particle accelerator, which typically
has kicker magnets and RF cavities with kA currents and kV
voltages nearby.
A colleague developed a special low transfer impedance coax
cable for this sort of application. It had two screens with
intermediate magnetic shielding. It was unpleasant to work
with, because part of the magnetic shielding was a steel
spiral foil tape that was razor sharp. But it worked really
well.
Empirical observation always trumps theory for me. Did you ground [1]
the copper tubes or braids?
Both ends were connected to the connector shields. The point of
the exercise was to reduce transfer impedance, which at low
frequency (<1MHz) is simply proportional to screen resistance.
Jeroen Belleman
Two parallel coaxes can make an attenuator.
What was the coupled frequency response like?
Ah sorry, this message didn't seem to get sent...
At low frequency, the transfer ratio was simply the ratio
of screen resistance over characteristic impedance. At medium
frequencies, a few octaves roughly around 1MHz, there was a dip,
and above that a steady rise of about 10dB/decade.
Not all cables behaved the same. RG58 is poorly screened and
doesn't have the dip. UT141 had a very deep dip.
Details at
<https://jeroen.web.cern.ch/jeroen/coaxleakage/leakage.shtml>.
Jeroen Belleman
Very interesting results, Jeroen. Thanks for posting them.

Is the MF resonance due to the inductive and capacitive coupling
cancelling each other? (They're 180 degrees out of phase, of course.)

The frequency is way too low to be a transmission line effect in a 1-m
length.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com
Jeroen Belleman
2024-05-18 12:19:49 UTC
Permalink
Post by Jeroen Belleman
Post by John Larkin
On Wed, 15 May 2024 11:03:22 +0200, Jeroen Belleman
Post by Jeroen Belleman
Post by Don
<snip>
Post by Jeroen Belleman
Post by Phil Hobbs
Post by John Larkin
Post by Don
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
I've been putting coax inside copper tubes or braids to measure
and/or reduce the transfer impedance (leakage). I did that to
measure small signals in a particle accelerator, which typically
has kicker magnets and RF cavities with kA currents and kV
voltages nearby.
A colleague developed a special low transfer impedance coax
cable for this sort of application. It had two screens with
intermediate magnetic shielding. It was unpleasant to work
with, because part of the magnetic shielding was a steel
spiral foil tape that was razor sharp. But it worked really
well.
Empirical observation always trumps theory for me. Did you ground [1]
the copper tubes or braids?
Both ends were connected to the connector shields. The point of
the exercise was to reduce transfer impedance, which at low
frequency (<1MHz) is simply proportional to screen resistance.
Jeroen Belleman
Two parallel coaxes can make an attenuator.
What was the coupled frequency response like?
Ah sorry, this message didn't seem to get sent...
At low frequency, the transfer ratio was simply the ratio
of screen resistance over characteristic impedance. At medium
frequencies, a few octaves roughly around 1MHz, there was a dip,
and above that a steady rise of about 10dB/decade.
Not all cables behaved the same. RG58 is poorly screened and
doesn't have the dip. UT141 had a very deep dip.
Details at
<https://jeroen.web.cern.ch/jeroen/coaxleakage/leakage.shtml>.
Jeroen Belleman
Very interesting results, Jeroen.  Thanks for posting them.
Is the MF resonance due to the inductive and capacitive coupling
cancelling each other?  (They're 180 degrees out of phase, of course.)
The frequency is way too low to be a transmission line effect in a 1-m
length.
Cheers
Phil Hobbs
The original data came from an HP3577 and I recorded only the
magnitude. Since this looks like a resonance, that's also what
I'd expect.

I can't easily go back and look again. I did this in 2009, and
I'm now retired. At the time, I was trying to make a choice for
cables connecting beam trajectory pick-ups in the CERN PSB to
their pre-amplifiers.

I suppose -but did not verify- that the dip is a resonance of
the outer inductance with a parasitic capacitance of my setup,
with the screen resistance as the damping element. I can't quite
make it fit that model though. The screen resistance doesn't
differ enough between, for example, UT141 and RG58 to explain a
deep resonance for the former, and its total absence for the
latter.

Jeroen Belleman
Phil Hobbs
2024-05-18 15:17:22 UTC
Permalink
Post by Jeroen Belleman
Post by Jeroen Belleman
Post by John Larkin
On Wed, 15 May 2024 11:03:22 +0200, Jeroen Belleman
Post by Jeroen Belleman
Post by Don
<snip>
Post by Jeroen Belleman
Post by Phil Hobbs
Post by John Larkin
Post by Don
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
I've been putting coax inside copper tubes or braids to measure
and/or reduce the transfer impedance (leakage). I did that to
measure small signals in a particle accelerator, which typically
has kicker magnets and RF cavities with kA currents and kV
voltages nearby.
A colleague developed a special low transfer impedance coax
cable for this sort of application. It had two screens with
intermediate magnetic shielding. It was unpleasant to work
with, because part of the magnetic shielding was a steel
spiral foil tape that was razor sharp. But it worked really
well.
Empirical observation always trumps theory for me. Did you ground [1]
the copper tubes or braids?
Both ends were connected to the connector shields. The point of
the exercise was to reduce transfer impedance, which at low
frequency (<1MHz) is simply proportional to screen resistance.
Jeroen Belleman
Two parallel coaxes can make an attenuator.
What was the coupled frequency response like?
Ah sorry, this message didn't seem to get sent...
At low frequency, the transfer ratio was simply the ratio
of screen resistance over characteristic impedance. At medium
frequencies, a few octaves roughly around 1MHz, there was a dip,
and above that a steady rise of about 10dB/decade.
Not all cables behaved the same. RG58 is poorly screened and
doesn't have the dip. UT141 had a very deep dip.
Details at
<https://jeroen.web.cern.ch/jeroen/coaxleakage/leakage.shtml>.
Jeroen Belleman
Very interesting results, Jeroen.  Thanks for posting them.
Is the MF resonance due to the inductive and capacitive coupling
cancelling each other?  (They're 180 degrees out of phase, of course.)
The frequency is way too low to be a transmission line effect in a 1-m
length.
Cheers
Phil Hobbs
The original data came from an HP3577 and I recorded only the
magnitude. Since this looks like a resonance, that's also what
I'd expect.
I can't easily go back and look again. I did this in 2009, and
I'm now retired. At the time, I was trying to make a choice for
cables connecting beam trajectory pick-ups in the CERN PSB to
their pre-amplifiers.
I suppose -but did not verify- that the dip is a resonance of
the outer inductance with a parasitic capacitance of my setup,
with the screen resistance as the damping element. I can't quite
make it fit that model though. The screen resistance doesn't
differ enough between, for example, UT141 and RG58 to explain a
deep resonance for the former, and its total absence for the
latter.
Jeroen Belleman
Plus you had some pretty frou-frou RG58 there, with foil and two braids.

The normal stuff is one tinned-copper braid with about 80% coverage. You
can probably make a directional coupler with a pair of patch cords and some
heat shrink. (I should try that.)

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
John Larkin
2024-05-18 16:00:09 UTC
Permalink
On Sat, 18 May 2024 15:17:22 -0000 (UTC), Phil Hobbs
Post by Phil Hobbs
Post by Jeroen Belleman
Post by Jeroen Belleman
Post by John Larkin
On Wed, 15 May 2024 11:03:22 +0200, Jeroen Belleman
Post by Jeroen Belleman
Post by Don
<snip>
Post by Jeroen Belleman
Post by John Larkin
Post by Don
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
I've been putting coax inside copper tubes or braids to measure
and/or reduce the transfer impedance (leakage). I did that to
measure small signals in a particle accelerator, which typically
has kicker magnets and RF cavities with kA currents and kV
voltages nearby.
A colleague developed a special low transfer impedance coax
cable for this sort of application. It had two screens with
intermediate magnetic shielding. It was unpleasant to work
with, because part of the magnetic shielding was a steel
spiral foil tape that was razor sharp. But it worked really
well.
Empirical observation always trumps theory for me. Did you ground [1]
the copper tubes or braids?
Both ends were connected to the connector shields. The point of
the exercise was to reduce transfer impedance, which at low
frequency (<1MHz) is simply proportional to screen resistance.
Jeroen Belleman
Two parallel coaxes can make an attenuator.
What was the coupled frequency response like?
Ah sorry, this message didn't seem to get sent...
At low frequency, the transfer ratio was simply the ratio
of screen resistance over characteristic impedance. At medium
frequencies, a few octaves roughly around 1MHz, there was a dip,
and above that a steady rise of about 10dB/decade.
Not all cables behaved the same. RG58 is poorly screened and
doesn't have the dip. UT141 had a very deep dip.
Details at
<https://jeroen.web.cern.ch/jeroen/coaxleakage/leakage.shtml>.
Jeroen Belleman
Very interesting results, Jeroen.  Thanks for posting them.
Is the MF resonance due to the inductive and capacitive coupling
cancelling each other?  (They're 180 degrees out of phase, of course.)
The frequency is way too low to be a transmission line effect in a 1-m
length.
Cheers
Phil Hobbs
The original data came from an HP3577 and I recorded only the
magnitude. Since this looks like a resonance, that's also what
I'd expect.
I can't easily go back and look again. I did this in 2009, and
I'm now retired. At the time, I was trying to make a choice for
cables connecting beam trajectory pick-ups in the CERN PSB to
their pre-amplifiers.
I suppose -but did not verify- that the dip is a resonance of
the outer inductance with a parasitic capacitance of my setup,
with the screen resistance as the damping element. I can't quite
make it fit that model though. The screen resistance doesn't
differ enough between, for example, UT141 and RG58 to explain a
deep resonance for the former, and its total absence for the
latter.
Jeroen Belleman
Plus you had some pretty frou-frou RG58 there, with foil and two braids.
The normal stuff is one tinned-copper braid with about 80% coverage. You
can probably make a directional coupler with a pair of patch cords and some
heat shrink. (I should try that.)
Cheers
Phil Hobbs
A practical question is what might the coupling be between two close,
parallel coaxes.
Phil Hobbs
2024-05-18 18:16:48 UTC
Permalink
Post by John Larkin
On Sat, 18 May 2024 15:17:22 -0000 (UTC), Phil Hobbs
Post by Phil Hobbs
Post by Jeroen Belleman
Post by Jeroen Belleman
Post by John Larkin
On Wed, 15 May 2024 11:03:22 +0200, Jeroen Belleman
Post by Jeroen Belleman
Post by Don
<snip>
Post by Jeroen Belleman
Post by John Larkin
Post by Don
The parasitic capacitance created between coax and its metal
armor can
open a Pandora's box of potential problems.
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky
shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
If the whole system is really coaxial, that’s true. Leaky
shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
I've been putting coax inside copper tubes or braids to measure
and/or reduce the transfer impedance (leakage). I did that to
measure small signals in a particle accelerator, which typically
has kicker magnets and RF cavities with kA currents and kV
voltages nearby.
A colleague developed a special low transfer impedance coax
cable for this sort of application. It had two screens with
intermediate magnetic shielding. It was unpleasant to work
with, because part of the magnetic shielding was a steel
spiral foil tape that was razor sharp. But it worked really
well.
Empirical observation always trumps theory for me. Did you ground [1]
the copper tubes or braids?
Both ends were connected to the connector shields. The point of
the exercise was to reduce transfer impedance, which at low
frequency (<1MHz) is simply proportional to screen resistance.
Jeroen Belleman
Two parallel coaxes can make an attenuator.
What was the coupled frequency response like?
Ah sorry, this message didn't seem to get sent...
At low frequency, the transfer ratio was simply the ratio
of screen resistance over characteristic impedance. At medium
frequencies, a few octaves roughly around 1MHz, there was a dip,
and above that a steady rise of about 10dB/decade.
Not all cables behaved the same. RG58 is poorly screened and
doesn't have the dip. UT141 had a very deep dip.
Details at
<https://jeroen.web.cern.ch/jeroen/coaxleakage/leakage.shtml>.
Jeroen Belleman
Very interesting results, Jeroen.  Thanks for posting them.
Is the MF resonance due to the inductive and capacitive coupling
cancelling each other?  (They're 180 degrees out of phase, of course.)
The frequency is way too low to be a transmission line effect in a 1-m
length.
Cheers
Phil Hobbs
The original data came from an HP3577 and I recorded only the
magnitude. Since this looks like a resonance, that's also what
I'd expect.
I can't easily go back and look again. I did this in 2009, and
I'm now retired. At the time, I was trying to make a choice for
cables connecting beam trajectory pick-ups in the CERN PSB to
their pre-amplifiers.
I suppose -but did not verify- that the dip is a resonance of
the outer inductance with a parasitic capacitance of my setup,
with the screen resistance as the damping element. I can't quite
make it fit that model though. The screen resistance doesn't
differ enough between, for example, UT141 and RG58 to explain a
deep resonance for the former, and its total absence for the
latter.
Jeroen Belleman
Plus you had some pretty frou-frou RG58 there, with foil and two braids.
The normal stuff is one tinned-copper braid with about 80% coverage. You
can probably make a directional coupler with a pair of patch cords and some
heat shrink. (I should try that.)
A practical question is what might the coupling be between two close,
parallel coaxes.
Since I now have a 3-GHz VNA, I might have a try measuring that. The
coupled amplitude goes like a cosine, so it’s easy to calculate how much
interaction length you need for 100% coupling from just one measurement.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
Jeroen Belleman
2024-05-18 20:49:32 UTC
Permalink
Post by Phil Hobbs
Post by Jeroen Belleman
Post by Jeroen Belleman
Post by John Larkin
On Wed, 15 May 2024 11:03:22 +0200, Jeroen Belleman
Post by Jeroen Belleman
Post by Don
<snip>
Post by Jeroen Belleman
Post by Phil Hobbs
Post by John Larkin
Post by Don
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
I've been putting coax inside copper tubes or braids to measure
and/or reduce the transfer impedance (leakage). I did that to
measure small signals in a particle accelerator, which typically
has kicker magnets and RF cavities with kA currents and kV
voltages nearby.
A colleague developed a special low transfer impedance coax
cable for this sort of application. It had two screens with
intermediate magnetic shielding. It was unpleasant to work
with, because part of the magnetic shielding was a steel
spiral foil tape that was razor sharp. But it worked really
well.
Empirical observation always trumps theory for me. Did you ground [1]
the copper tubes or braids?
Both ends were connected to the connector shields. The point of
the exercise was to reduce transfer impedance, which at low
frequency (<1MHz) is simply proportional to screen resistance.
Jeroen Belleman
Two parallel coaxes can make an attenuator.
What was the coupled frequency response like?
Ah sorry, this message didn't seem to get sent...
At low frequency, the transfer ratio was simply the ratio
of screen resistance over characteristic impedance. At medium
frequencies, a few octaves roughly around 1MHz, there was a dip,
and above that a steady rise of about 10dB/decade.
Not all cables behaved the same. RG58 is poorly screened and
doesn't have the dip. UT141 had a very deep dip.
Details at
<https://jeroen.web.cern.ch/jeroen/coaxleakage/leakage.shtml>.
Jeroen Belleman
Very interesting results, Jeroen.  Thanks for posting them.
Is the MF resonance due to the inductive and capacitive coupling
cancelling each other?  (They're 180 degrees out of phase, of course.)
The frequency is way too low to be a transmission line effect in a 1-m
length.
Cheers
Phil Hobbs
The original data came from an HP3577 and I recorded only the
magnitude. Since this looks like a resonance, that's also what
I'd expect.
I can't easily go back and look again. I did this in 2009, and
I'm now retired. At the time, I was trying to make a choice for
cables connecting beam trajectory pick-ups in the CERN PSB to
their pre-amplifiers.
I suppose -but did not verify- that the dip is a resonance of
the outer inductance with a parasitic capacitance of my setup,
with the screen resistance as the damping element. I can't quite
make it fit that model though. The screen resistance doesn't
differ enough between, for example, UT141 and RG58 to explain a
deep resonance for the former, and its total absence for the
latter.
Jeroen Belleman
Plus you had some pretty frou-frou RG58 there, with foil and two braids.
The normal stuff is one tinned-copper braid with about 80% coverage. You
can probably make a directional coupler with a pair of patch cords and some
heat shrink. (I should try that.)
Cheers
Phil Hobbs
This was Draka's version of RG58, I think it was made to CERN's
specs, fire retardant and rad-hard. From an RF standpoint, it
wasn't so fancy and it didn't fit very well in standard RG58-
compatible connectors.

Speaking of directional couplers, I made one with bits of UT85.
It was inspired by a 1979 publication by Udo Barabas in IEEE
Transactions on Microwave Theory and Techniques. It worked
surprisingly well, with a measured transmission bandwidth of
40kHz to 9GHz, although the directivity deteriorated beyond a
GHz or so. It was a rough demo of the concept. I'm sure it's
possible to do much better. It was my suggestion for a GHz
bandwidth beam position signal processing front-end in the
LHC.

I wrote it up in <https://jeroen.web.cern.ch/jeroen/Barabas/>.

Jeroen Belleman

Phil Hobbs
2024-05-14 23:49:45 UTC
Permalink
Post by Jeroen Belleman
Post by Phil Hobbs
Post by John Larkin
Post by Don
Post by Phil Hobbs
Post by Don Y
I've several short (a few feet) lengths of RG6 that I
would like to "strongly coerce" into assuming a particular
dressing.
Securing the cables to a stationary surface isn't practical
without significantly lengthening them and distorting
their "natural" routing.
But, ISTM that I should be able to slip each cable into
a comparable diameter copper (?) pipe and then use traditional
tools to bend that pipe into the appropriate configuration.
I'd have to observe constraints like minimum bend radius
but are there other issues that I might "discover" down the
road?
You’re planning to make a random- length shotgun balun.
Bazooka balun.
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Danke,
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
Cheers
Phil Hobbs
I've been putting coax inside copper tubes or braids to measure
and/or reduce the transfer impedance (leakage). I did that to
measure small signals in a particle accelerator, which typically
has kicker magnets and RF cavities with kA currents and kV
voltages nearby.
A colleague developed a special low transfer impedance coax
cable for this sort of application. It had two screens with
intermediate magnetic shielding. It was unpleasant to work
with, because part of the magnetic shielding was a steel
spiral foil tape that was razor sharp. But it worked really
well.
Jeroen Belleman
Interesting, thanks.

Is that better than real solid copper hardline or (my fave) RG402
semi-hardline?

I’d like to read more about it, if you have a reference handy.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
Jeroen Belleman
2024-05-15 09:07:04 UTC
Permalink
Post by Phil Hobbs
Post by Jeroen Belleman
Post by Phil Hobbs
Post by John Larkin
Post by Don
Post by Phil Hobbs
Post by Don Y
I've several short (a few feet) lengths of RG6 that I
would like to "strongly coerce" into assuming a particular
dressing.
Securing the cables to a stationary surface isn't practical
without significantly lengthening them and distorting
their "natural" routing.
But, ISTM that I should be able to slip each cable into
a comparable diameter copper (?) pipe and then use traditional
tools to bend that pipe into the appropriate configuration.
I'd have to observe constraints like minimum bend radius
but are there other issues that I might "discover" down the
road?
You’re planning to make a random- length shotgun balun.
Bazooka balun.
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Danke,
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
Cheers
Phil Hobbs
I've been putting coax inside copper tubes or braids to measure
and/or reduce the transfer impedance (leakage). I did that to
measure small signals in a particle accelerator, which typically
has kicker magnets and RF cavities with kA currents and kV
voltages nearby.
A colleague developed a special low transfer impedance coax
cable for this sort of application. It had two screens with
intermediate magnetic shielding. It was unpleasant to work
with, because part of the magnetic shielding was a steel
spiral foil tape that was razor sharp. But it worked really
well.
Jeroen Belleman
Interesting, thanks.
Is that better than real solid copper hardline or (my fave) RG402
semi-hardline?
I’d like to read more about it, if you have a reference handy.
I did some comparative tests. The results are here:
<https://jeroen.web.cern.ch/jeroen/coaxleakage/leakage.shtml>.
There are a few references too.

Jeroen Belleman
Don
2024-05-17 03:40:17 UTC
Permalink
Post by Jeroen Belleman
Post by Phil Hobbs
Post by Jeroen Belleman
Post by Phil Hobbs
Post by John Larkin
Post by Don
Post by Phil Hobbs
Post by Don Y
I've several short (a few feet) lengths of RG6 that I
would like to "strongly coerce" into assuming a particular
dressing.
Securing the cables to a stationary surface isn't practical
without significantly lengthening them and distorting
their "natural" routing.
But, ISTM that I should be able to slip each cable into
a comparable diameter copper (?) pipe and then use traditional
tools to bend that pipe into the appropriate configuration.
I'd have to observe constraints like minimum bend radius
but are there other issues that I might "discover" down the
road?
You?re planning to make a random- length shotgun balun.
Bazooka balun.
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
I've been putting coax inside copper tubes or braids to measure
and/or reduce the transfer impedance (leakage). I did that to
measure small signals in a particle accelerator, which typically
has kicker magnets and RF cavities with kA currents and kV
voltages nearby.
A colleague developed a special low transfer impedance coax
cable for this sort of application. It had two screens with
intermediate magnetic shielding. It was unpleasant to work
with, because part of the magnetic shielding was a steel
spiral foil tape that was razor sharp. But it worked really
well.
Interesting, thanks.
Is that better than real solid copper hardline or (my fave) RG402
semi-hardline?
I’d like to read more about it, if you have a reference handy.
<https://jeroen.web.cern.ch/jeroen/coaxleakage/leakage.shtml>.
There are a few references too.
To summarize:

Apparently Jeroen uses CK50 sheathed in copper tubing while his
colleague's cable is CKB50. The transfer impedance of all tested coax
cables converge at about 54 MHz - a cable channel's common lower
frequency range.

Don Y's primary takeaway from this thread may be to solder both ends
of his conformal copper to the coax screen underneath.

Danke,
--
Don, KB7RPU, https://www.qsl.net/kb7rpu
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.
Don Y
2024-05-15 02:51:38 UTC
Permalink
Post by Jeroen Belleman
I've been putting coax inside copper tubes or braids to measure
and/or reduce the transfer impedance (leakage). I did that to
measure small signals in a particle accelerator, which typically
has kicker magnets and RF cavities with kA currents and kV
voltages nearby.
But you likely weren't ALSO relying on the tubing for it's
mechanical characteristics?

I see no real electrical issues -- a copper pipe is just
a third (for RG6U) or fifth (for RG6'q') shield layer.
But, its (desired!) inflexibility adds other complications
to its deployment.

- it inherently eliminates any "service loop" so the
endpoints are fixed, spatially, wrt each other.
So, positioning those points then becomes important
along with its constraints on their disconnection!
(imagine having two or more such connections between
"end devices", potentially orthogonal to each other!)
- it transfers any mechanical stresses encountered
along its length to the supporting endpoints which
likely weren't designed with that sort of "mechanical
load" in mind (you're supposed to have a CABLE connected
there, not some "cantilevered mass"). A passerby
bumping it anywhere along its length poses a risk.
- it makes on-site manufacture (by "semi-trained
installers) more difficult -- e.g., fabricating the
cable *inside* the tubing (few folks are proficient in
handling EMT and *that* has much less constraints;
how much does the inner cable "shrink" with each bend?)

I assume your deployment was "one-off", done by someone
skilled in the practice (or, at least able to evaluate
the quality of their FINISHED work) and likely isolated
from other "traffic"? You likely wouldn't expect some
"jamoke" to be able to install it correctly? (dealing with
the consumer market is a whole different set of challenges)

It's also been suggested that "tubing" may not be rigid
enough for my needs -- any impacts might deform it and
leave lasting stresses on the connections. I will buy some
type K (the thickest wall tubing commonly available, here)
and see how much abuse it can take.

I've been directed to explore plastic solutions as
an alternative. And, technologies that would allow
some of the critical dimensions to be avoided in
their (on-site) manufacture. Sadly, ENT isn't (?)
available in such small diameters... Maybe PVC??

Or, sell "assemblies" which means having to settle on
a small number of configurations and expecting the
market to adapt to them. :<
Post by Jeroen Belleman
A colleague developed a special low transfer impedance coax
cable for this sort of application. It had two screens with
intermediate magnetic shielding. It was unpleasant to work
with, because part of the magnetic shielding was a steel
spiral foil tape that was razor sharp. But it worked really
well.
Bill Sloman
2024-05-18 13:52:40 UTC
Permalink
<snip>
Post by Jeroen Belleman
I've been putting coax inside copper tubes or braids to measure
and/or reduce the transfer impedance (leakage). I did that to
measure small signals in a particle accelerator, which typically
has kicker magnets and RF cavities with kA currents and kV
voltages nearby.
A colleague developed a special low transfer impedance coax
cable for this sort of application. It had two screens with
intermediate magnetic shielding. It was unpleasant to work
with, because part of the magnetic shielding was a steel
spiral foil tape that was razor sharp. But it worked really
well.
RG402 and RG405 semirigid coaxial cable has been around for ages.

https://www.awcwire.com/rg-catalog/rg402-coax-cable

With SMA soldered-on connectors it is good to 22GHz, and a solid copper
tube as as a outer screen is pretty effective. Some people do have a
passion for re-inventing the wheel.
--
Bill Sloman, Sydney
John Larkin
2024-05-15 00:29:47 UTC
Permalink
On Tue, 14 May 2024 21:46:35 -0000 (UTC), Phil Hobbs
Post by John Larkin
Post by Don
Post by Phil Hobbs
Post by Don Y
I've several short (a few feet) lengths of RG6 that I
would like to "strongly coerce" into assuming a particular
dressing.
Securing the cables to a stationary surface isn't practical
without significantly lengthening them and distorting
their "natural" routing.
But, ISTM that I should be able to slip each cable into
a comparable diameter copper (?) pipe and then use traditional
tools to bend that pipe into the appropriate configuration.
I'd have to observe constraints like minimum bend radius
but are there other issues that I might "discover" down the
road?
You?re planning to make a random- length shotgun balun.
Bazooka balun.
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Danke,
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
Cheers
Phil Hobbs
Why can't he just use tie-wraps? Or hot-melt?
Phil Hobbs
2024-05-15 01:52:34 UTC
Permalink
Post by John Larkin
On Tue, 14 May 2024 21:46:35 -0000 (UTC), Phil Hobbs
Post by John Larkin
Post by Don
Post by Phil Hobbs
Post by Don Y
I've several short (a few feet) lengths of RG6 that I
would like to "strongly coerce" into assuming a particular
dressing.
Securing the cables to a stationary surface isn't practical
without significantly lengthening them and distorting
their "natural" routing.
But, ISTM that I should be able to slip each cable into
a comparable diameter copper (?) pipe and then use traditional
tools to bend that pipe into the appropriate configuration.
I'd have to observe constraints like minimum bend radius
but are there other issues that I might "discover" down the
road?
You?re planning to make a random- length shotgun balun.
Bazooka balun.
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Danke,
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that’s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
Why can't he just use tie-wraps? Or hot-melt?
What a simplistic suggestion!

This is the Yuniskis world we’re talking about, where nothing is ever so
simple as it might seem.

You might as well suggest that Baer get a new computer!

(And in my world, RG-58 cables talk to each other all the time.)

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
John Larkin
2024-05-15 03:51:09 UTC
Permalink
On Wed, 15 May 2024 01:52:34 -0000 (UTC), Phil Hobbs
Post by Phil Hobbs
Post by John Larkin
On Tue, 14 May 2024 21:46:35 -0000 (UTC), Phil Hobbs
Post by John Larkin
Post by Don
Post by Phil Hobbs
Post by Don Y
I've several short (a few feet) lengths of RG6 that I
would like to "strongly coerce" into assuming a particular
dressing.
Securing the cables to a stationary surface isn't practical
without significantly lengthening them and distorting
their "natural" routing.
But, ISTM that I should be able to slip each cable into
a comparable diameter copper (?) pipe and then use traditional
tools to bend that pipe into the appropriate configuration.
I'd have to observe constraints like minimum bend radius
but are there other issues that I might "discover" down the
road?
You?re planning to make a random- length shotgun balun.
Bazooka balun.
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Danke,
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
If the whole system is really coaxial, that?s true. Leaky shields, ground
loops, and so on, will modify that.
Depending on the application, you may or may not care.
Why can't he just use tie-wraps? Or hot-melt?
What a simplistic suggestion!
Thank you.

The more one engineers something, the simpler it should get.
Don
2024-05-14 22:20:56 UTC
Permalink
Post by John Larkin
Post by Don
Post by Phil Hobbs
Post by Don Y
I've several short (a few feet) lengths of RG6 that I
would like to "strongly coerce" into assuming a particular
dressing.
Securing the cables to a stationary surface isn't practical
without significantly lengthening them and distorting
their "natural" routing.
But, ISTM that I should be able to slip each cable into
a comparable diameter copper (?) pipe and then use traditional
tools to bend that pipe into the appropriate configuration.
I'd have to observe constraints like minimum bend radius
but are there other issues that I might "discover" down the
road?
You?re planning to make a random- length shotgun balun.
Bazooka balun.
The parasitic capacitance created between coax and its metal armor can
open a Pandora's box of potential problems.
Capacitance between the coax outer and the copper pipe? Proper coax
shouldn't have any external field.
Does a ferrite bead by any other name (eg metal armor) contain parasitic
capacitance?

... A ferrite bead can be modeled as a simplified circuit
consisting of resistors, an inductor, and a capacitor ...

<https://www.analog.com/en/resources/analog-dialogue/articles/ferrite-beads-demystified.html>

Danke,
--
Don, KB7RPU, https://www.qsl.net/kb7rpu
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.
Clive Arthur
2024-05-15 15:05:00 UTC
Permalink
Post by Don Y
I've several short (a few feet) lengths of RG6 that I
would like to "strongly coerce" into assuming a particular
dressing.
Securing the cables to a stationary surface isn't practical
without significantly lengthening them and distorting
their "natural" routing.
But, ISTM that I should be able to slip each cable into
a comparable diameter copper (?) pipe and then use traditional
tools to bend that pipe into the appropriate configuration.
I'd have to observe constraints like minimum bend radius
but are there other issues that I might "discover" down the
road?
How about semi-rigid adhesive lined heat shrink tubing?

https://www.farnell.com/datasheets/3758112.pdf
--
Cheers
Clive
Don Y
2024-05-15 16:22:47 UTC
Permalink
Post by Clive Arthur
Post by Don Y
I've several short (a few feet) lengths of RG6 that I
would like to "strongly coerce" into assuming a particular
dressing.
Securing the cables to a stationary surface isn't practical
without significantly lengthening them and distorting
their "natural" routing.
How about semi-rigid adhesive lined heat shrink tubing?
https://www.farnell.com/datasheets/3758112.pdf
I'd have to look at it but can't imagine it would be any
stiffer than RG6 itself.

Part of the problem IS that stiffness; you can't impose a
particular shape on the cable that it will keep without
some other "enforcement". E.g., if you were to directly mate
to a wall-mounted F-connector, you'd want to quickly bring
the cable back towards the wall (to keep it from interfering
with the other items using that "space"). You will, eventually,
get back to the wall about 6 inches from that connection
point (2" minimum bend radius; do the geometry).

Now, you can connect to a splitter -- which can be fastened
to that same wall (or, a coplanar surface). A few inches later,
each output from the splitter will now have to find its way to
its respective destination, avoiding any other devices that
it encounters on that route and assuming an economical path
to that destination.

Then, the *second* wall-mounted F-connector can similarly
snake around the cabling and devices for the first to
find *its* devices. Noting, of course, that each such
device somehow has to get its power and make its network
connection (i.e., more boxes and cables in the way).

Canvassing friends and neighbors, it seems that cable TV,
satellite TV and OTA broadcasts are delivered to the home
this way. In various combinations depending on the occupant's
preferences and usage patterns.

E.g., one of my neighbors has "cable" for his internet connection,
OTA (roof-mounted antenna) for local TV (and radio!) and satellite
for his "foreign" TV. Another neighbor has satellite and cable
for his "domestic" TV (sports junkies) and internet.

In a two-person household, it seems like 3 tuners are a minimum.
This assumes two people watching (different programs) and one
being recorded.

[Here, SWMBO often ties up two tuners recording concurrent
programs while I opt to watch a third "live"]

In a four-person household (i.e., kids), add another 2 or 3
tuners. Recall that, even if the same program is being watched
by two occupants ON DIFFERENT TVs, each will want to be able
to channel-surf without interfering with the other's viewing.

Five (or more) tuners (cable or OTA) currently require at least
two physical devices. And, don't forget the cable modem! (I
assume satellite receivers can be similarly configured).

A TV tuner (cable or OTA) won't give you any "radio" capabilities
so add devices for that.

So, figure 7 (2+2 different types of TV, 2 radio, 1 modem) physical
devices have to be wired to some number of F-connectors protruding
from the wall. (and powered and accessed electronically)

And, you want to put this pile of kit someplace out of the way,
yet accessible. Professional in appearance. And, maintainable
(not a hodge-podge of /ad hoc/ wiring). Instead of having an STB
at *each* TV, a separate HiFi "somewhere", a modem sitting in your
living room BEHIND that TV, etc.

So, someplace like a closet, pantry, basement, attic, garage, etc.
None of which were likely intended to house those bits of kit. Many
basements are "unfinished", have sparse power distribution, etc.
All (?) closets are devoid of power -- often true of pantries
and cupboards, as well. Garages are often not "living spaces"
(so, are subject to temperature extremes). I.e., houses aren't
designed with "equipment rooms" in mind (industrial and commercial
deployments are a piece of cake, by comparison!). So, you are
intruding on OTHER uses for that space.

Empirically, it seems like you need a bit less than a square foot
of "surface" for each device and it's cabling -- IF you can dress
all of the cabling nice and tight. (and, assuming you are a
conscientious "installer"!)

[Remember, YOU don't manufacture any of these devices so have
to adapt to the mechanical configurations of THEIR manufacturers!]

And, this is just the run-of-the-mill devices that you're already
using...
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