After looking at both Steve Hunt and Jim Browns material in depth, I have a general question. In regard to the many various 1:1 choke baluns on both their sites, has anybody actually measured the uh
Jim, Yes - I've measured the inductance using a low frequency meter "just for fun"; but that's what it was - "just for fun" - it tells you little about the high frequency CM impedance of a choke, for
choke. I was just interested to know how much uh you folks are seeing on these bigger CM chokes, where 5-15 turns of coax are used on 4-8 cores, that type of scenario. The only torroid CM choke I ha
With 7 turns of RG58 on four stacked FT240-31 cores I measure 298uH. That's broadly consistent with Fair-Rite's published figure for the Initial Permeability (1500). Steve G3TXQ CM Z of a choke. I wa
On 10/30/2014 3:22 AM, Jim Thomson wrote: I realize the uh, measured at low freqs tells me little about the CM Z of a choke. I was just interested to know how much uh you folks are seeing on these bi
I have a spreadsheet which does pretty much what Jim just described. One thing that interested me when I started looking at the "best fit" equivalent-circuit values was that the value of C varied dep
Variables include the turn spacing, the diameter of the choke, diectric constant of the cable outer insulator, the dielectric constant of the core material, and the portion of the winding influenced
Jim, If I wind exactly the same number of turns of the same cable with identical spacing on the same-size toroids, but use two different core materials, I get very different values of equivalent C. T
Author: TexasRF--- via TowerTalk <towertalk@contesting.com>
Date: Fri, 31 Oct 2014 12:30:33 -0400
Steve, is equivalent C something you measure or is it calculated? If measured, how do you do that? If calculated, how do you do that? Thanks, Gerald K5GW In a message dated 10/31/2014 9:10:52 A.M. Pa
Gerald, I measured the choke resonant frequency using a 2-port VNA S21 measurement. I then calculated what the choke series-equivalent resistance and inductance would be at that resonant frequency us
I have yet to find a swept antenna analyzer or VNA that will measure chokes correctly above about 10 MHz, and I've tried that the the DG8SAQ VNWA. I don't have access to the good (and very expensive)
I agree that simple S11 impedance measurements tend to produce false (low) resonant frequencies. And the higher the Q of the choke the bigger the error. But I can wind a high-Q air-cored choke, measu
Just to develop this a little further .... I referred earlier to a spreadsheet I had produced that allows me to specify the number of turns, the number of stacked cores and the stray C of a choke usi
Steve and Jim, Both of you gentlemen are recognized as very knowledgeable on the subject of chokes. So for those of us looking for testing guidance in brief, what is a good way to determine the resul
Hi Ray, Here's a sketch of the test set-up I use with my VNA2180: http://www.karinya.net/g3txq/temp/s21/vna.png The choke under test fits between terminals A and B. If you compare it with Fig 40a (Pa
I was just asked by PM what Rt is in my sketch here: http://www.karinya.net/g3txq/temp/s21/vna.png For others who may be wondering it is part of the representation of the choke. In other words the im
I mentioned earlier the importance of the phase information provided by the VNA - it not only allows the choke R and X to be identified, but it also eliminates a measurement error in |Z| inherent at
A number of folk have expressed interest via PMs in the spreadsheet I use to perform the calculation of choke R and X from the VNA data. In case there is wider interest it's available here: http://ww