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RF Power Splitter Using Two Ferrite Toroids
Ken Moorman
I believe that someone on this group sent an email to the group several days ago with an attachment which showed the schematic of and a photo of an rf power splitter using a couple of small ferrite toroids. I have managed to misplace that message and wonder if the original sender (or anyone who might have saved it) would send it to me or provide me with the link to find it on the groups.io site. My email address is nu4i AT cox.net. Thanks.
Ken, NU4I |
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RF Sampler
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 |
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Re: MY CMC MEASUREMENT
#measurement
On Mon, Feb 8, 2021 at 03:02 PM, David Eckhardt wrote:
David, Thanks for: "our measurements look much like mine." Followed Yours and K6JCA, W2DU, G3TXQ and other Experts recommendations... only with my nanoVNA " Miro, OK for "MnZn" it was my tipomistake Please read my post again.I only and only talked / wrote about the voltage and power of the peaks.At the peaks,the toroid and the coils are loaded with this voltage and power. The dog is buried there. This is the maximum and real stress that the choke experiences at the peaks.The arcing between wires is always on the peaks. 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. KEY DOWN ON CW is very good test....Nothing less, nothing more.. I can't say Best Regards ! Thanks for the Comments ! |
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Re: CMC MEASUREMENTS - PDF'ed & SIZE REDUCED
OMG!!
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No topic drift, no politics, no name calling, just chat about our favorite topics! There _are_ some reasonable people left alive!! I have found my nirvana on groups.io... What a wonderful group to have found, thank you all! 73, and thanks, Dave (NK7Z) ARRL Volunteer Examiner ARRL Technical Specialist, RFI ARRL Asst. Director, NW Division, Technical Resources On 2/8/21 4:02 PM, David Eckhardt wrote:
Don, I absolutely love your tongue-in-cheek (well, I do understand) |
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Re: CMC MEASUREMENTS - PDF'ed & SIZE REDUCED
Don, I absolutely love your tongue-in-cheek (well, I do understand)
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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 --
*Dave - W?LEV* *Just Let Darwin Work* |
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Re: CMC MEASUREMENTS - PDF'ed & SIZE REDUCED
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 |
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Re: MY CMC MEASUREMENT
#measurement
Your measurements look much like mine.
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However, as has been previously pointed out, your power calculation is in error. 77-watts is the correct value. Dave - W?LEV On Sun, Feb 7, 2021 at 3:21 PM Peter Ivanooff <gp2zl2gpg@...> wrote:
In the mid-January, my old 80m dipole broke due to icing and heavy snow. --
*Dave - W?LEV* *Just Let Darwin Work* |
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Re: CMC MEASUREMENTS - PDF'ed & SIZE REDUCED
Thanks sir!!!
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73, and thanks, Dave (NK7Z) ARRL Volunteer Examiner ARRL Technical Specialist, RFI ARRL Asst. Director, NW Division, Technical Resources On 2/8/21 2:55 PM, David Eckhardt wrote:
There is a limited listing of ¦År for a few common dielectrics in any ARRL |
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Re: CMC MEASUREMENTS - PDF'ed & SIZE REDUCED
There is a limited listing of ¦År for a few common dielectrics in any ARRL
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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, --
*Dave - W?LEV* *Just Let Darwin Work* |
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Re: CMC MEASUREMENTS - PDF'ed & SIZE REDUCED
Hi,
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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,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. |
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Re: CMC MEASUREMENTS - PDF'ed & SIZE REDUCED
Gary,
I ask because I made a few measurements with a thermal probe on the side of aStrange. Flux density, and thus heat production, happens in the bulk of the ferrite, not just its surface. They are strongest where the magnetic path is shortest, and that's along the inside surface of a toroid, while along its outside surface flux density and heat production are minimal. In between there is close-to-linear distribution through the bulk of the core. Do you happen to know how much end-to-end voltage you had on that choke, when it got warm? According to my measurements and calculations, with 8 turns on that core, at 28MHz, it takes 194V end-to-end to cause a volumetric loss of 300mW/cm?, which equates to 8W total loss in that core, enough to heat it up reasonably fast. So that could be seen as a not-to-exceed value for ICAS service. In a 50? system where antenna balance is such that half of the signal voltage appears end-to-end, that's enough to handle legal limit power. But if the choke is used in a high impedance system, its power limit will be much lower. Jim, Skin depth is a thing, too. And since it's proportional to 1/sqrt(mu), higher mu makes the skin depth smaller. Fortunately it's proportional to sqrt(resistivity),Let's not forget that skin effect is a phenomenom that affects conductors. There is no such thing as skin effect in ferrites, which are essentially insulators. The reduction of skin effect with ? happens when the electric conductor is also a magnetic material, such as steel wire. I hope nobody here is using steel wire to wind CMCs! But copper-clad steel wire is OK, as long as the copper layer is plenty thick enough to accomodate the skin depth at the frequency of operation. About the dielectric loss in plastics: There are two families of plastics: Polar and non-polar ones. In polar plastics each molecule is electrically asymmetric, making it react strongly to electric fields and thus absorbing a lot of energy at RF, turning it into heath. In non-polar plastics each molecule is electrically balanced, drastically reducing the absorption of energy from RF electric fields. PVC and nylon are polar plastics, polyethylene and teflon are non-polar ones. Water is a polar molecule, and that's why water absorption in plastics increases their dielectric loss. But polar plastics have such high dielectric loss anyway that water absorption in them is probably of pretty low importance on their total dielectric loss. |
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Re: MORE CMC SINGLE CORE DATA
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@...> wrote: Your finding don't compare well with the data found here.-- *Dave - W?LEV* *Just Let Darwin Work* |
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Re: MORE CMC SINGLE CORE DATA
The CMCs I have constructed and measured are NOT coaxial cable wound on the
toroids which are presented in your reference. That presentation simply winds and measures (for the most part) RG-58 wound on the toroids. That's why I included the picture at the end to illustrate specifically what I was dealing with. That's the green PVC-insulated wire that heated badly with 400-watts. I have wound and measured and posted bifilar-wound chokes, NOT coax. These are NOT the same. Coaxially wound CMC are not true common mode chokes. They offer a reflective function (inductive) for the RF energy on the outer surface of the coaxial cable: a large +jX. 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. It is a bilateral device. 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. 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. 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. Dave - W?LEV On Mon, Feb 8, 2021 at 7:33 PM Max via groups.io <kg4pid@...> wrote: Your finding don't compare well with the data found here.-- *Dave - W?LEV* *Just Let Darwin Work* |
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Re: MORE CMC SINGLE CORE DATA
Your finding don't compare well with the data found here.
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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: |
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Re: Wireless remote control of nanoVNA-H
ALL the modules are 3.3 volt devices but many have low output regulators in front.
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Get the schematic for the one you have and bypass the regulator to run it directly from 3.3v On Monday, February 8, 2021, 2:20:28 p.m. EST, <rcrosbypa@...> wrote:
I can not find a low voltage HC-05 module such as the 3.3v. Where did you purchase your module? Everyone I've found on line are of the 3.6-6v modules. -Thanks |
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Re: CMC MEASUREMENTS - PDF'ed & SIZE REDUCED
On 2/8/21 10:56 AM, Dave Cole wrote:
Hi, 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, |
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Re: MY CMC MEASUREMENT
#measurement
On Sun, Feb 7, 2021 at 09:21 AM, Peter Ivanooff wrote:
Chances are that I'm not interpreting your setup correctly, but based on the picture with choke and nanoVNS, you were only testing the DM mode - impact of your choke on power sent from one side to the other side of your choke. You need to test the CM (common mode) suppression, and that get's done differently - for example, you short both sides Would be great if you can clarify your test setup and then mention what attached screens shots are for :) |
Gary W9TD
Don - KM4UDX
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