Discussion in 'Antennas, Feedlines, Towers & Rotors' started by SP3L, Jun 14, 2021.
Excel 2003...nothing like using 18 year old software. Are you running a Pentium Pro CPU too?
What a team !!
Jacek and Dan, many thanks for the joint to produce this fine tool.
73, Maximo - EA1DDO
shall we invite you too next time?
thank you very much for the measurement data. I will analyze it during the weekend.
If you do not mind, I will reply to you by email as this subject is too technical to bother all the readers of this thread.
Sure, we can communicate via e-mails. I sent my e-mail to yours, as per your QRZ.com page.
I thought of a way to set-up a "mildly" multi-turn measurement.
First and foremost I need to find a plastic former matching the dimensions of a two core assembly onto which 3 turns will be wound.
This could have been easy to 3D print if I had such a capability, but I don't have.
Three turns seem reasonable for keeping the impedance lower to 1kΩ where the RigExpert has a decent accuracy.
As inductance is proportional to the square of the number of turns, 4 of them on two cores will exceed 1kΩ.
Three measurement samples should be prepared: a) On the dummy former for OSL calibration b) On two same material cores and c) On two different material cores.
Three equal length wires shall be space-wound over the 2/3 of the core's circumference.
But, I will wait to hear from you first as this long week-end I will be away from home.
I think it is worth posting it also here.
There was a question on the other forum why we limited the number of cores to three. And here is my answer.
Using N cores does not increase the inductor impedance. Actually, it even slightly reduces it. Try calculating and displaying the following inductors:
1x #43: 2.4/0.5" 14T
2x #43: 2.4/0.5" 9T
3x #43: 2.4/0.5" 7T
If you increase the number of cores, you need fewer turns to achieve the same frequency coverage and your core has greater volume so it can dissipate more power. And that's it.
But if you take the same 3 cores, wind them individually and connect them in series - that's quite another story. Your total choke impedance will increase 3 times (3x|Z| and 3xR). That reduces both the common-mode current and the power that needs to be dissipated in the choke. And you again have three cores to dissipate heat but much less heat than before.
One more thing. Suppose that you calculated that every individual choke should have, say, 14 turns. You may decide to make three chokes having 13, 14 and 15 turns and connect them in series. In this way, your final choke will tolerate the spread of core permeability parameters to a higher degree. Such approach is especially recommended for the 50 and 60 materials which produce high Q inductors.
That's why I do not see much benefit in increasing the number of cores in the calculator.
Using cores made of different materials in one choke can be something else. I do not know yet but having Nikos measurement results I should be able understand how such configuration works.
Jacek, I appreciated the invitation, but you know, I am a beginner, learning everyday.
Thank you Jacek.
Your example is accurate Jacek, but your text on top of it is not.
"Using N cores does not increase the inductor impedance. Actually, it even slightly reduces it. Try calculating and displaying the following inductors"
When there are 2 or 3 cores (for the same inductance) each core undertakes 1/2 or 1/3 of the total. Also, the impedance is proportional to the square of the number of turns.
Consequently, SQR(1/2) = 0.707 and SQR(1/3) =0.577. Multiplying these two numbers by the original number of turns i.e. 14 we get the equivalencies of 9.89t for N=2 and 8.09t for N=3.
In your example these equivalences are compared with integral number of turns, there can't be any fractional turn, but lesser in numbers (9 vs 9.89 and 7 vs 8.09). Naturally less inductance results.
The core separation and cascading has other merits, like better cooling and less capacitive coupling between input and output that shunts the inductance.
The only drawback is more wire used which is actually a TL further changing the characteristics of the combo antenna + choke.
Owen Duffy commented on this question with an informative blog post.
Just a heads up to all on how to download the most recent version of calculator. Jacek is using Google Drive to host the download zip file. When an update is made, which was done yesterday to correct some very minor and non-critical errors in both the Help and the Calculator, the link to get the zip file will change.
So the link that was quoted by W4KJG in post #9 and by myself in post #37 is now obsolete but still active. And I won't specify a direct link to get the "v1.2.zip" since that too will become obsolete but still active at some point in the future.
As near as I can tell the only way to know you are downloading the "most recent" zip file is to use the link at the bottom of Jacek's TFCI Calculator web page. Perhaps Jacek can verify that and also perhaps move (or duplicate) the "Click here to download the calculator and its help file. Current version:" line to near the top of that web page.