开云体育

/g/NanoVNAV2/message/1147
On Tue, 9 Feb 2021 at 17:59, Max via groups.io <kg4pid@...>
wrote:

Sorry for the confusion on my part. I had forgotten about your
measurements being for the bifilar wound CMC, not a coax choke one.
G3TXQ said the RG-58 could be replaced with RG-400 with little change in
performance. That's what I use. I can't remember its power rating but it's
likely more than I'll ever need.
One thing I don't understand is how to tell if the CMC choke is resistive
at the frequency of interest.
Max KG4PID
On Monday, February 8, 2021, 03:29:04 PM CST, David Eckhardt <
davearea51a@...> wrote:

RG-58 is not appropriate for US amateur legal power. I don't use it.
This is one of the main reasons I have chosen bifilar wound CMCs.

I have enough RG-142 (Teflon silver coated and double shielded 50-ohm coax
that will take power) to try one good choke wound in the manner of your
referenced presentation. I can try that and present the results.

Dave - W?LEV

On Mon, Feb 8, 2021 at 7:33 PM Max via groups.io <kg4pid=
[email protected]>
wrote:

Your finding don't compare well with the data found here.

Look at the 12 and 17 turn on RG58.
Max KG4PID


On Sunday, February 7, 2021, 01:16:30 PM CST, Mel Farrer via

groups.io

<farrerfolks@...> wrote:

Hi, Dan,
My experience with the 240-31 core with 14 T RG 303 gives me ~7K at 160,

13K on 80/40, slowly rolling off to >4 K at 28 MHz Still >5 K on 12 .

Mel, K6KBE
On Sunday, February 7, 2021, 10:53:04 AM PST, Dan Schaefer W3BU <
clancy.987@...> wrote:

Don
Still curious about the 5k across 10 to 160?
Been reading the mail and has been fun but it isn’t obvious to me you get
5k across the whole band? When you get time it might be fun to discuss
your definitions for the 5k.
Have been enjoying the discussion threads but currently a bit time

limited

to engage.
Enjoy.
Dan. W3BU

On Jan 17, 2021, at 9:49 AM, Don - KM4UDX <dontAy155@...> wrote:

groups.io/g/nanovna-users/wiki
-=-=-

--
*Dave - W?LEV*
*Just Let Darwin Work*

On Feb 9, 2021, at 12:47 PM, David Eckhardt <davearea51a@...> wrote:

?If you just want to monitor what your antenna is radiating, a 24" clip lead
formed in a loop works fine for RF pickup into an o'scope.? Connect one end
of the clip lead to the BNC backshell and the other to the center of the
BNC.? While it is not a quantitative sampler, it will capture plenty of
energy to assess the quality of your radiated RF energy.? Otherwise, the
Collins Radio solution looks pretty spiff and easy to build.

Dave - W?LEV

On Tue, Feb 9, 2021 at 3:07 PM Max via groups.io <kg4pid@...>
wrote:

I need an RF sampler of some sort for monitoring my RF signal. This might
be used with a scope or TinySA or ...
Is something like this what I need? If so I'd prefer to build by own if I
can get some info on the core type and number of turns and such. If this
isn't what I need, what would this be used for exactly?



Thanks Max

--
*Dave - W?LEV*
*Just Let Darwin Work*

On Feb 9, 2021, at 12:47 PM, David Eckhardt <davearea51a@...> wrote:

?If you just want to monitor what your antenna is radiating, a 24" clip lead
formed in a loop works fine for RF pickup into an o'scope. Connect one end
of the clip lead to the BNC backshell and the other to the center of the
BNC. While it is not a quantitative sampler, it will capture plenty of
energy to assess the quality of your radiated RF energy. Otherwise, the
Collins Radio solution looks pretty spiff and easy to build.

Dave - W?LEV

On Tue, Feb 9, 2021 at 3:07 PM Max via groups.io <kg4pid@...>
wrote:

I need an RF sampler of some sort for monitoring my RF signal. This might
be used with a scope or TinySA or ...
Is something like this what I need? If so I'd prefer to build by own if I
can get some info on the core type and number of turns and such. If this
isn't what I need, what would this be used for exactly?



Thanks Max

--
*Dave - W?LEV*
*Just Let Darwin Work*

? Your finding don't compare well with the data found here.



Look at the 12 and 17 turn on RG58.
Max KG4PID


? ? On Sunday, February 7, 2021, 01:16:30 PM CST, Mel Farrer via groups.io
<farrerfolks@...> wrote:

? Hi,? Dan,
My experience with the 240-31 core with 14 T RG 303 gives me ~7K at 160,

13K on 80/40, slowly rolling off to >4 K at 28 MHz Still >5 K on 12 .

Mel, K6KBE
? ? On Sunday, February 7, 2021, 10:53:04 AM PST, Dan Schaefer W3BU <
clancy.987@...> wrote:

? Don
Still curious about the 5k across 10 to 160?
Been reading the mail and has been fun but it isn’t obvious to me you get
5k across the whole band?? When you get time it might be fun to discuss
your definitions for the 5k.
Have been enjoying the discussion threads but currently a bit time limited
to engage.
Enjoy.
Dan.? W3BU

On Jan 17, 2021, at 9:49 AM, Don - KM4UDX <dontAy155@...> wrote:

groups.io/g/nanovna-users/wiki
-=-=-

Don, I absolutely love your tongue-in-cheek (well, I do understand)
response! I really do!!!
Some of us had to suffer through learning calculus and then applying it to
electromagnetic theory and antennas and transmission lines. My references
now are graduate level. Yes, we suffered, but at this end of life, I'm
glad I *once* (stress: ONCE) did.
You are to be commended in your response which reflects the audience to
which I attempted to target. If I can't pass along some of the knowledge I
gained in formal education followed by decades of seat-of-the-pants
learning during my career applying what I learned while suffering, I'm
ready for the pine box.
Thank you for your reply!!!!!! You should take up satirical writing.
Dave - W?LEV
On Mon, Feb 8, 2021 at 11:53 PM Don - KM4UDX <dontay155@...> wrote:

As a non-engineer (of any type) like other nano-users, the simple mission
was to wind some coax or wire around a ferrite donut installed on our OCFD
and stop the nasty, dreaded, feared, sneaky and often discussed common mode
current from creating shack mayhem.

The intended process? Copy the designs of others and validate with our
nanos.

The actual process: sink into a putrid pit of RF theory, irreconcilable
contradictions, arcania, mystery with misery, and a odd desire to plunge an
ice pick in our eye because it would feel better than trying to understand
how to (a) build a CMC and (b) measure our newly minted CM choke
effectiveness over the lowly average ham bands (say 80-10m) with our
beloved nanos.

I, and others, read and study Dave's (W0LEV)'s work like Orthodox study
the Talmud - every letter, every grouping of words, even the space between
words, has intense meaning to the lost, abandoned and hopeless neophytes.

All this is to say thank you Dave, and others. Your work is light to
sheep lost in inky blackness.

My favorite professor would say at the end of every lecture to a class
clearly dazed, befuddled and confused: ..."okay, clear as mud?" Followed by
"Good, see you next week!"

Don
Km4udx

As a non-engineer (of any type) like other nano-users, the simple mission
was to wind some coax or wire around a ferrite donut installed on our OCFD
and stop the nasty, dreaded, feared, sneaky and often discussed common mode
current from creating shack mayhem.

The intended process? Copy the designs of others and validate with our
nanos.

The actual process: sink into a putrid pit of RF theory, irreconcilable
contradictions, arcania, mystery with misery, and a odd desire to plunge an
ice pick in our eye because it would feel better than trying to understand
how to (a) build a CMC and (b) measure our newly minted CM choke
effectiveness over the lowly average ham bands (say 80-10m) with our
beloved nanos.

I, and others, read and study Dave's (W0LEV)'s work like Orthodox study
the Talmud - every letter, every grouping of words, even the space between
words, has intense meaning to the lost, abandoned and hopeless neophytes.

All this is to say thank you Dave, and others. Your work is light to
sheep lost in inky blackness.

My favorite professor would say at the end of every lecture to a class
clearly dazed, befuddled and confused: ..."okay, clear as mud?" Followed by
"Good, see you next week!"

Don
Km4udx

In the mid-January, my old 80m dipole broke due to icing and heavy snow.
It had a direct connection with a coax for too many years .... and I
decided to be with a Choke when the Weater improve.I started tests with
several noname ferrite toroids and nanoVNA-H v.3.3. After some
measurements (according to Fair Rite ) the toroides turned out to be MgZn,
40x25x11mm with Initial ?i 2000 or a bit more.
Stacked two with 14 turns 1.12 mm enameled wire in thermo shrink tubing
(max diameter 2mm - the toroids are small). Normal winding .... tested and
Reisert style... the same result.To avoad fixture capacitance I connected
the Choke
direct to calibrated plane of nanoVNA CH0 - CH1.
Used nanoVNA alone, after with NanoVNA Saver, and OneofEleven application.
Full House with Data ...I've made a try to burn the choke with my PA and
250W
noninductive dummy load (with some pauses).KEY Down on CW and 175 volts
p/p on Tektronix osci.
That is 612 watts on the peaks....The core and windings were cold as
before the test ...I know the real test is up on the feedpoint of the
antenna....
Seems the Choke can be used on 3.5Mhz- never have had 1.8 Mhz.Only
3.5-432Mhz.
The screenshots are attached.
Will be good some Expert to say something about this Choke....till I
waiting for FT240-31 toroids.

Best Regards !

There is a limited listing of εr for a few common dielectrics in any ARRL
Handbook. For a more extensive listing I'd refer you to the CRC Handbook
of Chemistry and Physics published by the CRC Press. About any edition
will do. There are also good online sources.
Dave - W?LEV
On Mon, Feb 8, 2021 at 10:45 PM Dave Cole <dave@...> wrote:

Hi,

Thanks for the detail!!! If you find that study on various dialectic
values for various materials, I would love a copy... I am making some
VLF and HF ferrite bar antenna, and using CPVC to protect the ferrite,
and as a coil form.

73, and thanks,
Dave (NK7Z)

ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources

On 2/8/21 11:12 AM, Jim Lux wrote:

On 2/8/21 10:56 AM, Dave Cole wrote:

Hi,
Thanks for the clarification, do you think this is due to the PVC
itself absorbing water, or just moisture in the air?

A little of both - moisture adsorbing into the surface will increase
surface leakage for HV, but after wiping it down with alcohol, the
leakage resistance was still higher, so I think there's some bulk
absorption into the plastic. Another indication is that blowing warm
dry air on it takes a while to get the leakage back down. This is in
low current HV applications (Electrostatic machines like Van de Graaff
generators or Kelvin water droppers), where 1 microamp is a lot of
current, so driving leakages low is important.


I'll have to go look, but someone did a study measuring the Q of tesla
coil secondaries on various form materials as the weather varied.
Cardboard (sonotube) varies a lot, but I can't remember how PVC pipe
worked.


My "take home" from this was "choose a different kind of plastic for
those applications"

For the "plastic pipe in a microwave" I think it's more bulk absorption
into the porosity - plastic pipe is not pure PVC, after all. It's PVC +
fillers + dye, and with no attention to bulk dielectric properties.

In most RF applications (e.g. antennas) using PVC pipe is probably fine
- there's a lot of other things that will dominate over any small
dielectric losses, and whether the leakage is microamps or 10s of
microamps is probably not worth worrying about. I've not worried about
it much. I don't think I'd use it as a substrate for a conformal patch
antenna, though. It's too easy and cheap to get something you know will
work better.

73, and thanks,
Dave (NK7Z)

ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources

On 2/8/21 10:34 AM, Jim Lux wrote:

The leakage resistance changes noticeably with humidity.

Hi,

Thanks for the detail!!! If you find that study on various dialectic
values for various materials, I would love a copy... I am making some
VLF and HF ferrite bar antenna, and using CPVC to protect the ferrite,
and as a coil form.

73, and thanks,
Dave (NK7Z)

ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources

On 2/8/21 11:12 AM, Jim Lux wrote:

On 2/8/21 10:56 AM, Dave Cole wrote:

Hi,
Thanks for the clarification, do you think this is due to the PVC
itself absorbing water, or just moisture in the air?

A little of both - moisture adsorbing into the surface will increase
surface leakage for HV, but after wiping it down with alcohol, the
leakage resistance was still higher, so I think there's some bulk
absorption into the plastic. Another indication is that blowing warm
dry air on it takes a while to get the leakage back down. This is in
low current HV applications (Electrostatic machines like Van de Graaff
generators or Kelvin water droppers), where 1 microamp is a lot of
current, so driving leakages low is important.


I'll have to go look, but someone did a study measuring the Q of tesla
coil secondaries on various form materials as the weather varied.
Cardboard (sonotube) varies a lot, but I can't remember how PVC pipe
worked.


My "take home" from this was "choose a different kind of plastic for
those applications"

For the "plastic pipe in a microwave" I think it's more bulk absorption
into the porosity - plastic pipe is not pure PVC, after all. It's PVC +
fillers + dye, and with no attention to bulk dielectric properties.

In most RF applications (e.g. antennas) using PVC pipe is probably fine
- there's a lot of other things that will dominate over any small
dielectric losses, and whether the leakage is microamps or 10s of
microamps is probably not worth worrying about. I've not worried about
it much. I don't think I'd use it as a substrate for a conformal patch
antenna, though. It's too easy and cheap to get something you know will
work better.

73, and thanks,
Dave (NK7Z)

ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources

On 2/8/21 10:34 AM, Jim Lux wrote:

The leakage resistance changes noticeably with humidity.