Coaxial Cable Coil Induction

[ion]

You may be referring to RG400 E.

Yes, that is pretty much looking like the stuff I have.

https://www.youtube.com/watch?time_continue=26&v=CGZDqDOEtM0

BTW everyone seems to have skipped over partzman's  post with nary a comment. Is COP 1.65 not interesting anymore?

[Verpies]

BTW everyone seems to have skipped over partzman's  post with nary a comment. Is COP 1.65 not interesting anymore?

He did not pursue it and implied, that his measurements at this frequency are not trustworthy.

[Verpies]

So what are your "expectations" ?  I would like to learn.

My expectations were in line with F6FLT and Smudge's
...however experiments show that induction IS happening.

What would you suggest to eliminate errors caused by capacitive coupling and coaxial cable imperfections ?

My idea for the latter is to insert a normal coax into a bendable but solid copper tubing, in order to make a very low-loss coax ( double shielded )  ...and retest.

...but how to quantify and control the capacitive coupling?

[poynt99]

My expectations were in line with F6FLT and Smudge
...however experiments show that induction IS happening.

What would you suggest to eliminate errors caused by capacitive coupling and coaxial cable imperfections ?

My idea for the latter is to insert a normal coax into a bendable but solid copper tubing, in order to make a very low-loss coax ( double shielded )  ...and retest.

...but how to quantify and control the capacitive coupling?

What frequency are you using?, and please clarify "cable imperfections".

[Verpies]

What frequency are you using?

~45MHz and pulses.

...and please clarify "cable imperfections".

Mainly, imperfect shielding.

[poynt99]

Mainly, imperfect shielding.

Leading to what effect?

[Verpies]

Leading to what effect?

EM radiation leaking outside of the coax

[gyula]

My expectations were in line with F6FLT and Smudge's
...however experiments show that induction IS happening.

What would you suggest to eliminate errors caused by capacitive coupling and coaxial cable imperfections ?

My idea for the latter is to insert a normal coax into a bendable but solid copper tubing, in order to make a very low-loss coax ( double shielded )  ...and retest.

...but how to quantify and control the capacitive coupling?

There is surely a measurable, some pF capacitance between the shield of the coax and any one end of the secondary coil wire.  I would suggest to form a parallel resonant circuit for 45.5 MHz with this capacitance by connecting two small RF toroidal coils as I indicate in your earlier drawing. 

The two coils should have resultant inductance appropiate for resonance with the capacitance at 45.5 MHz.

If the created galvanic connection between the coax and the secondary is not wanted, then a some hundred pF (or higher value) capacitor could be connected in series with each coil to eliminate galvanic connection.

Regarding the copper tubing, it is ok to shield the coax further on,  alternatively a cheaper solution would be to wind a Alu foil bandage around the coax cable in a few layers.  Self adhesive Alu tapes may also make fixing wire connections to such bandage a bit easier.

Gyula

[partzman]

He did not pursue it and implied, that his measurements at this frequency are not trustworthy.

I really didn't wish to derail your thread so I said little about the device.  However, I am very confident in my measurements as shown but simply was trying to say that it is Ok if nobody believes them.

Regards,
Pm

[gyula]

I really didn't wish to derail your thread so I said little about the device.  However, I am very confident in my measurements as shown but simply was trying to say that it is Ok if nobody believes them.

Regards,
Pm

Hi PM,

If your delay line device is off topic here, then would you consider some discussion on it at your own bench thread?

Thanks,
Gyula

[poynt99]

EM radiation leaking outside of the coax

If you are trying to minimize capacitive coupling, the easiest solution is to significantly lower your frequency. Why would 1kHz (or lower) not be suitable?

[partzman]

Hi PM,

If your delay line device is off topic here, then would you consider some discussion on it at your own bench thread?

Thanks,
Gyula

Gyula,

Sure, that would be fine.  I'll open a new thread on my bench tomorrow.

Regards,
Pm

[Apecore]

Guys,

What do you expect to be induced in the inner solid helical coil when the outer helical coil is wound with an ideal coaxial cable, which is driven symmetrically from an isolated secondary of an RF transformer from one end, and terminated with a resistance R on the other end ?
Both helical windings are coaxial with respect to each other.

1) When R=0
2) When R= the characteristic impedance of the coaxial cable
3) When R=∞

A) When the coaxial cable is driven by a CW signal having a period equal to an integer multiple of halfwavelengths of this piece of cable.
B) When the coaxial cable is driven by a CW signal having a period equal to the quarter wavelength of this piece of cable.
C) When the coax is pulsed with a very short pulse (e.g. 1/100 of its wavelength).

The 50cent coin starts to fall.
I have not the slidest idea but I feel something is brewing