开云体育

Halloooo.... miro - Your answers are nagging. Only bla, bla, bla.
Every very, а very little smart student will understand what I talking for ! Only for Peaks ! See the attachment now- to learn what is Peak for AC voltage.
And No, my till 3 Ghz dummy load is 5000 Ohms ! Special chip resistor on solid
5000 Ohm radiator too. Ha, ha , ha...you never will get such
The Power was enough to burn balls of brass monkey like you.Use Internet calculator to calculate how much peak power 175 volts on peak gives.

I built this one but cannot get linear. As in output was way too low at 80m to be usable 10 m was the same. Ok on 20/17/15

Adrian VK4KL

Two home-made couplers are shown in the attached photos; that will give some ideas on construction.

Construction details are shown on one photo. #43 ferrite will give very similar results.

Performance is also shown; they are good to about 120 MHz.

These are 30dB couplers and, unlike the ebay one, are not terminated at the Cpl port; they are used with a 50-ohm power meter or other 50-ohm instrument which provides the necessary termination.

Never operate this kind of coupler un-terminated, ie with the Cpl port open; very high voltages will be generated.

A through power of 100W (+50dBm) will produce 50 - 30 = +20dBm at the Cpl port; if this is excessive, attenuators can be used.

On Sat, Feb 6, 2021 at 04:00 PM, David Eckhardt wrote:

It was requested by a number of responders that I convert to PDF. The
attachments are in .PDF format which should be able to be read by
everyone.

There was also a request to place them in the files section of these
NANOVNA sites. I am a member and will attempt that. However, if the
moderators don't see them there, please place them there.

Dave - W?LEV

Dave,

Thank you for the great summary and information about measure CMC CM attenuation. I have a couple of follow up questions for you and/or the group, if I may. I notice the process is for bifilar chokes. And, it looks like you only connect one wire of the bifilar turns to the VNA. You also said you can connect both wires if you short both ends. I am still trying to make sense of shorting both wires and why their wouldn't be a difference in CM impedance compared to only connecting one wire. To me, it would seem that connecting both ends together would create a parallel path and would not be a true measurement of impedance (i.e. due to wires in parallel, similar to two resistors in parallel). But, I know we are dealing RF and ferrite toroids ... my intuition can't make that jump, yet.

Second question, what is the procedure for coax chokes? I *think* what I have seen and understand is that you connect the *braid* only on CH0 and CH1 (Port 1 and Port 2). This is the path that the CM would take. Is this correct for coax chokes?

I have the NanoVNA and love it. Building and measuring CMCs is my next adventure. Thanks to you and the group for a wonderful resource.

73,
Adam - N0KTB

Coaxially wound CMC are not true common mode chokes.

I differ on that point. I claim that they are true CMCs, just like
bifiliarly wound ones. They do suppress common mode current on a coax cable
just as well as on a bifiliar one. Thus they tend to force the currents on
both conductors to be of the same amplitude and opposite phase, regardless
of whether the two conductors are arranged side-by-side or
one-around-the-other.

Yes, they do suppress CM current as does a bifilarly wound
choke. However, a coasially wound choke has absolutely no influence on the
currents and fields inside the coaxial cable. A
coaxial cable is in reality a 3-conductor topology (providing
conductors are of good quality and thick enough to negate skin effect):
1) Outside of the outer conductor, 2) Inside of the
outer conductor, and 3) outside surface of the inner
conductor. The coaxially wound CMC has no effect in currents or fields
internal to the coaxial cable. So, yes, currents on the
appropriate surfaces on the inside of the coax cable have the
correct amplitude and phase relationship, but are not influenced by
anything on the outside of the inner cylindrical
volume.

reflective function (inductive) for the RF energy on the outer surface of
the coaxial cable: a large +jX.

I would like to simply do away with the distinction between currents on the
outside or the inside of the outer conductor, because it's irrelevant. We
cannot separate them at the ends.

This is precisely the reason a choke is required to prevent outer
currents from coupling into the antenna structure.

And anyway, whenever the operating frequency is low enough, and the outer
conductor is thin enough so that it's thinner than the skin depth, there
physically isn't any separate current, but just ONE SINGLE current in the
outer conductor. And a CMC wound with coax cable can work both below and
above the limit frequency above which separate currents can exist on the
outside and inside of the outer conductor.

Only Radio Shack marketed coax that was so leaky with only 40%
braid coverage that it conformed to your hypothetical 'low frequency'
limit. I can not disagree with your arguement,
but hopefully amateurs do not use such bad coax cable. BTW:
"ported coax" (commercial product of leaky coax) is marketed and used for
comms in mine tunnels and as a perimeter
sensor for fissile material storage on KAFB in Albuquerque (it
turned out to be rather unreliable due to varying moisture conditions of
the soil).

Furthermore the distinction is irrelevant for this reason: At high
frequencies and with thick outer conductors, the current on the inside of
the outer conductor automatically is equal and opposite to the current on
the inner conductor, regardless of whether or not there is a CMC.

True

The CMC will then suppress current on the outside. And at low frequencies
in a coax cable having a thin outer conductor, there is just one current in
the outer conductor, which can be different from the current on the inner
conductor, but a CMC will force them to be the same. So, the end effect is
that regardless of whether those separate currents can exist or not, the
CMC works the same. We just don't need to care about where exactly the
outer conductor's current flows.

If there is current on the outer surface of the outer braid,
without a choke, that energy seen a high impedance (depending on conductor
lengths) and will couple into the antenna
structure. It will also participate in radiation of the energy
in transmit which should be only the function of the antenna alone, not
antenna plus coax.

The low-frequency or fat conductor arguments, I can not disagree
with. However, neither apply to amateur applications, unless one has left
over coax from Radio Shack. The typical
amateur simply does not knowingly use such 'bad' coax.

As such, they function as a current
'balun' reflecting the energy with a bit of absorption as well. A true

CMC

accepts CM energy (coaxial cable, for example) at one port and 'outputs'

DM

energy (equal amplitude with opposite phases) at the opposite port.

I can't agree with that logic. I can't see how a CMC, by itself, can turn
CM energy into DM energy.

The functoon of a balun or CMC regardless of its construction is
to do away with the currents and energy on the outside of the coaxial
braid. For the intended energy (received or
transmitted - bidirectionality), the Zo from either end is 50
non-reactive ohms in a coaxially fed system. This does not apply to those
of us who use a single set of wires fed with open
wire for all HF bands. In that case, the load end in transmit is
all over the Smith Chart. At any rate, with a coaxially fed system, both
ends are at 50±j0 ohms. We agree there is
current and energy being transported along the outside of the
outer braid. When this energy bounces between the source and load, it
likely is anything bot 50±j0 ohms. Depending on
coaxial lengths and lwngth of the 'antenna' conductor directly
connected to the coaxial braid, that external energy may be high or low
impedance or something in between and likely
quite reactive. Place a very high Z between the outer fields and
the antenna which is at (assumed) 50±j0 ohms and very little of the energy
will couple to the antenna structure. that is
what the CMC choke or current balun accomplishes. From a circuit
standpoint:

Low-Z -----> High Z ------> Low-Z Where the high-Z
is the CMC or choke balun, it functions as a reflective element. Energy
sourced from the left low-Z can't "get through" the
high-Z to the right low-Z. It is a large +jX in most cases. It
could be a true resistor which would be an absorptive element, but that
would require a dissipation of sizable for a full legal
source.

Anyway energy involves voltage and time in addition to current. Letting the
time aside, which means disregarding the confusion between energy and
power, to talk about CM energy we need some external conductor (usually
earth) to complete the circuit. As soon as such an external conductor is
involved, we can no longer talk about the CMC doing anything, because it's
the whole circuit that's doing it.

Power is defined as energy delivered over time. 1 Watt = 1 Joule
(of energy) delivered over a span of 1-second (BTW, irregardless of
impedance). The three variables can not be
separated.

So, does the space station require a 'ground*'* connection to
transmet bidirectionally between orbit and earth stations? Does Cassiopia
require a 'ground' connection to fill deep space
with RF energy? Do all the deep space hydrogen clouds require a
'ground' connection to fill deep space with copious amounts of 1.42 GHz
energy (I'm receiving just that as I write.)?
The misconception is that antennas require a 'ground' connection
to properly radiate or receive RF energy and currents require a return, but
no 'ground' connection is required. Nor do
I require a 'ground' connection to receive the 1.42 GHz hydrogen
emission from deep space. Nor does a dipole require a 'ground' to radiate
and receive RF energy.

Dave - W?LEV

On Tue, Feb 9, 2021 at 8:48 PM Manfred Mornhinweg <manfred@...> wrote:

Dave,

I can't resist replying again, and challenging some of your points.

Coaxially wound CMC are not true common mode chokes.

I differ on that point. I claim that they are true CMCs, just like
bifiliarly wound ones. They do suppress common mode current on a coax cable
just as well as on a bifiliar one. Thus they tend to force the currents on
both conductors to be of the same amplitude and opposite phase, regardless
of whether the two conductors are arranged side-by-side or
one-around-the-other.

They offer a
reflective function (inductive) for the RF energy on the outer surface of
the coaxial cable: a large +jX.

I would like to simply do away with the distinction between currents on
the outside or the inside of the outer conductor, because it's irrelevant.
We cannot separate them at the ends. And anyway, whenever the operating
frequency is low enough, and the outer conductor is thin enough so that
it's thinner than the skin depth, there physically isn't any separate
current, but just ONE SINGLE current in the outer conductor. And a CMC
wound with coax cable can work both below and above the limit frequency
above which separate currents can exist on the outside and inside of the
outer conductor.

Furthermore the distinction is irrelevant for this reason: At high
frequencies and with thick outer conductors, the current on the inside of
the outer conductor automatically is equal and opposite to the current on
the inner conductor, regardless of whether or not there is a CMC. The CMC
will then suppress current on the outside. And at low frequencies in a coax
cable having a thin outer conductor, there is just one current in the outer
conductor, which can be different from the current on the inner conductor,
but a CMC will force them to be the same. So, the end effect is that
regardless of whether those separate currents can exist or not, the CMC
works the same. We just don't need to care about where exactly the outer
conductor's current flows.

As such, they function as a current
'balun' reflecting the energy with a bit of absorption as well. A true

CMC

accepts CM energy (coaxial cable, for example) at one port and 'outputs'

DM

energy (equal amplitude with opposite phases) at the opposite port.

I can't agree with that logic. I can't see how a CMC, by itself, can turn
CM energy into DM energy. Anyway energy involves voltage and time in
addition to current. Letting the time aside, which means disregarding the
confusion between energy and power, to talk about CM energy we need some
external conductor (usually earth) to complete the circuit. As soon as such
an external conductor is involved, we can no longer talk about the CMC
doing anything, because it's the whole circuit that's doing it.

It is a bilateral device.

Yes. Any CMC is.

A bifilar wound CMC accomplishes the function of a
coaxially wound choke PLUS ensuring the DM required balance in amplitude
and phase at the DM side of the choke. This is accomplished by a
'feedback' mechanism between the transmission line on the toroid and the
induced magnetic currents within the core.

I absolutely disagree on that. There is nothing in a CMC wound with
bifiliar line that would force such balance. At least not in a "clean" CMC
that works reasonably free from parasitic effects. If you connect one port
of a balanced-wound CMC to a ground-referenced signal source, and the other
end to two different load resistors to ground, then the ground-referenced
voltages on those two resistors will NOT be equal.Just the currents will be
the same.

And if you do the same exercise with a coax-wound CMC, you will get the
same results. Except if you have such strong parasitics (such as stray
capacitance) that they dominate over the desired effects. But in that case
you have a badly designed CMC.

This 'feedback' mechanism which
functions in both directions ideally cancels core magnetic currents

induced

by each conductor of the bifilar windings. A coaxial 'balun' or current
balun such as coaxial cable wound on the core does not offer this
additional benefit of a bifilar wound CMC.

I disagree! The truth is that DM current causes no flux in the core,
while CM current does cause flux, and that this happens regardless of
whether the two conductors are side-by-side or coaxially arranged. For that
reason the winding impedance of a CMC opposes the flow of CM current, while
having no effect on the DM current. Again without any distinction between
coax and parallel line.

The true CMC works on the same principle as parallel wire transmission
line, but without any added and lumped magnetic material. The

interaction

between the two conductors of the oscillating RF field consisting of both
electric and magnetic fields on the line cancel eachother, resulting in

no

radiation from the transmission line but only transmission of the RF

energy

along the line. That's the physics (without the math) of the workings

of

a true CMC. The presence of the magnetic material - the toroid -
'concentrates' the magnetic field produced by the bifilar windings much
like a dielectric 'concentrates' the electric field (in the case of a
capacitor), both of which allow for application of a lumped circuit
function instead of a distributed circuit function.

I believe that what you are trying to point out here is that with parallel
wire the core does have some effect on the transmission effects along the
line, while with coax cable it doesn't, given that parallel line has much
of its field outside around the conductors, while coax line has it all
confined inside. That's true. But the effect of this is mainly that the
core will affect the impedance of the parallel line, if it's wound with the
conductors very close to the core, while a coax cable is immune to this. It
doesn't cause any effect on the fundamental action as a CMC.

CMC using parallel line should be wound with a reasonable spacing between
the conductors and the core, to avoid increasing the transmission loss, and
changing the line's impedance. Coax cable instead can be tight-wound around
the core without a loss penalty nor a change in impedance. Of course only
as long as its bending radius doesn't end up too small, but that's yet
another effect that has nothing to do with what we are discussing here...

So I maintain that a winding of coax cable on a magnetic core makes a
fully valid CMC, that even has some advantages over a CMC wound with
parallel line. I don't accept that using parallel line to wind a CMC
fundamentally produces any additional balancing effect.

Manfred

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

On Tue, Feb 9, 2021 at 02:10 AM, Peter Ivanooff wrote:

PA - Tube with 1900 volts on Anode/ 0.5 A plate current (DC) when the PI
filter
is set to max output power on 3.65 Mhz..
LOAD - 250 watts non-inductive load up to 3 Ghz on a solid radiator (I had to
pause so as not to blow it) is heated to 80 degrees Celsius for 30 seconds
Nonstop test.The Choke NO - it remained relatively cold.

Just to get us "more scientific" and enable others to use and rely on your experience, would be great if you can provide "set up and measurements" in SI units instead of in descriptive statements :)

1) Power dissipation of the PA (tube) can be irelevantan - it only tells how much heat will dissipate inside the amplifier. Without knowing how much power was "send" by the power supply, or even better how efficient is the amp, we can't conculde how much power was sent to your dummy load

2) I suppose that your dummy load is 50 ohm

3) Stated power of the load (250W) does not tell much. It's usually "power rating for given duty cycle" (for example: 100W @1hr, 250W @1min, 1000W @2sec)

The most helpful will be if you can connect your oscilloscope to the dummy load (mind the max voltage prorated for frequency) and measure either "peak to peak" or "max" voltage.

Keep in mind that "p-p" (between + and - maximum) is double of "max" (zero to maximum).

From that, it will be easy to calculate the power your balun is handling as P = (Vmax/1.4)^2 / 50.

If you expect that that you have 250W delivered to your load, you should see Vpp = 2*1.4*sqrt(250*50) = 313V

OK, guys and gals..... I wound 13 turns of RG-142 on two stacked 240-43
cores. That's all I could somewhat gracefully wind on the cores. I've got
roughly 3' of unwound RG142 out one side as I didn't want to cut my length
of that cable. RG-142 is a tad larger in outer diameter, is silver plated,
double shielded, and uses Teflon dielectric. Measured values are as
follows:

Frequency (MHz) DM Loss (dB) CM Loss (dB)

1.9 All ≤0.15 -26
3.75 -34
7.15 -44
10.1 -42
14.2 -38
18.1 -34
21.3 -30
28.4 -23

Dave - W?LEV

Dave,

I can't resist replying again, and challenging some of your points.

Coaxially wound CMC are not true common mode chokes.

I differ on that point. I claim that they are true CMCs, just like bifiliarly wound ones. They do suppress common mode current on a coax cable just as well as on a bifiliar one. Thus they tend to force the currents on both conductors to be of the same amplitude and opposite phase, regardless of whether the two conductors are arranged side-by-side or one-around-the-other.

They offer a
reflective function (inductive) for the RF energy on the outer surface of
the coaxial cable: a large +jX.

I would like to simply do away with the distinction between currents on the outside or the inside of the outer conductor, because it's irrelevant. We cannot separate them at the ends. And anyway, whenever the operating frequency is low enough, and the outer conductor is thin enough so that it's thinner than the skin depth, there physically isn't any separate current, but just ONE SINGLE current in the outer conductor. And a CMC wound with coax cable can work both below and above the limit frequency above which separate currents can exist on the outside and inside of the outer conductor.

Furthermore the distinction is irrelevant for this reason: At high frequencies and with thick outer conductors, the current on the inside of the outer conductor automatically is equal and opposite to the current on the inner conductor, regardless of whether or not there is a CMC. The CMC will then suppress current on the outside. And at low frequencies in a coax cable having a thin outer conductor, there is just one current in the outer conductor, which can be different from the current on the inner conductor, but a CMC will force them to be the same. So, the end effect is that regardless of whether those separate currents can exist or not, the CMC works the same. We just don't need to care about where exactly the outer conductor's current flows.

As such, they function as a current
'balun' reflecting the energy with a bit of absorption as well. A true CMC
accepts CM energy (coaxial cable, for example) at one port and 'outputs' DM
energy (equal amplitude with opposite phases) at the opposite port.

I can't agree with that logic. I can't see how a CMC, by itself, can turn CM energy into DM energy. Anyway energy involves voltage and time in addition to current. Letting the time aside, which means disregarding the confusion between energy and power, to talk about CM energy we need some external conductor (usually earth) to complete the circuit. As soon as such an external conductor is involved, we can no longer talk about the CMC doing anything, because it's the whole circuit that's doing it.

It is a bilateral device.

Yes. Any CMC is.

A bifilar wound CMC accomplishes the function of a
coaxially wound choke PLUS ensuring the DM required balance in amplitude
and phase at the DM side of the choke. This is accomplished by a
'feedback' mechanism between the transmission line on the toroid and the
induced magnetic currents within the core.

I absolutely disagree on that. There is nothing in a CMC wound with bifiliar line that would force such balance. At least not in a "clean" CMC that works reasonably free from parasitic effects. If you connect one port of a balanced-wound CMC to a ground-referenced signal source, and the other end to two different load resistors to ground, then the ground-referenced voltages on those two resistors will NOT be equal.Just the currents will be the same.

And if you do the same exercise with a coax-wound CMC, you will get the same results. Except if you have such strong parasitics (such as stray capacitance) that they dominate over the desired effects. But in that case you have a badly designed CMC.

This 'feedback' mechanism which
functions in both directions ideally cancels core magnetic currents induced
by each conductor of the bifilar windings. A coaxial 'balun' or current
balun such as coaxial cable wound on the core does not offer this
additional benefit of a bifilar wound CMC.

I disagree! The truth is that DM current causes no flux in the core, while CM current does cause flux, and that this happens regardless of whether the two conductors are side-by-side or coaxially arranged. For that reason the winding impedance of a CMC opposes the flow of CM current, while having no effect on the DM current. Again without any distinction between coax and parallel line.

The true CMC works on the same principle as parallel wire transmission
line, but without any added and lumped magnetic material. The interaction
between the two conductors of the oscillating RF field consisting of both
electric and magnetic fields on the line cancel eachother, resulting in no
radiation from the transmission line but only transmission of the RF energy
along the line. That's the physics (without the math) of the workings of
a true CMC. The presence of the magnetic material - the toroid -
'concentrates' the magnetic field produced by the bifilar windings much
like a dielectric 'concentrates' the electric field (in the case of a
capacitor), both of which allow for application of a lumped circuit
function instead of a distributed circuit function.

I believe that what you are trying to point out here is that with parallel wire the core does have some effect on the transmission effects along the line, while with coax cable it doesn't, given that parallel line has much of its field outside around the conductors, while coax line has it all confined inside. That's true. But the effect of this is mainly that the core will affect the impedance of the parallel line, if it's wound with the conductors very close to the core, while a coax cable is immune to this. It doesn't cause any effect on the fundamental action as a CMC.

CMC using parallel line should be wound with a reasonable spacing between the conductors and the core, to avoid increasing the transmission loss, and changing the line's impedance. Coax cable instead can be tight-wound around the core without a loss penalty nor a change in impedance. Of course only as long as its bending radius doesn't end up too small, but that's yet another effect that has nothing to do with what we are discussing here...

So I maintain that a winding of coax cable on a magnetic core makes a fully valid CMC, that even has some advantages over a CMC wound with parallel line. I don't accept that using parallel line to wind a CMC fundamentally produces any additional balancing effect.

Manfred

Frank,
The eBay vendor does not look like he kept the shield on the coax for the faraday shield part.
Gary
W9TD

Gary,

I built this one. Not difficult to wind the coil. Testing is a good thing after completion. Looks like the eBay vendor is using this same design. It might come down to the difference between source pricing all new parts vs the eBay price, shipped.

73,

Frank
K4FMH

Does anyone know if G3TXQs numbers are the same for 8x as for 58? I.E. can I sub 8x for 58?

73, and thanks,
Dave (NK7Z)

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

On Tue, Feb 9, 2021 at 10:01 AM, Wa4kfz wrote:

This is an example of an RF tap used for sampling a signal.

Mark, thanks for posting this (you beat me!). Looking at the drawing in your first link, it's possible that my copper foil connects to the RF line rather than ground as I had described it.

Unfortunately, that tap is back at my house in Silicon Valley, so I can't verify. Here, at my "portable 6" QTH, my tap has no foil because a flat response isn't important to me for signal monitoring.

- Jeff, k6jca

I made a poor man's sampler.? I just put a loop around the coax and connect it to the scope.? There is plenty of rf even when operating barefoot.?

Bob K6DDX

Max, how much power are you driving?

I hate winding toroids, so for my transmitters in the 100 watts range, I just make a simple voltage divider (e.g. 10K & 50 ohms). 1 watt for the 10K should be fine for 100 watts continuous (brick on key) xmit power (the 10K's dissipation will be 0.5 watts if your transmit power is 100 watts into a matched load ), and the attenuation is 52 dB, assuming the 50 ohm lower-leg of the divider connects via coax to a 50-ohm terminated device (e.g. o'scope), which gives plenty of signal for my oscilloscope.

There will be some tilting of the sampled-signal's frequency response. If you need a flat response, I flatten mine over the HF range by placing a bit of grounded foil near the body of the 10K resistor (I use a piece copper-foil tape (with Kapton tape over the foil as an insulator), but you could try experimenting with a piece of insulated wire). Use your NanoVNA in S21 mode to adjust the foil's (or wire's) placement for a flat response.

I build mine into Pomona boxes.

- Jeff, k6jca

This is an example of an RF tap used for sampling a signal.





73,
Mark WA4KFZ

Try randl.com

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*

/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*

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

An article on this type of sampler is available here:

Gary
W9TD