Seems like he publishes the measured common-mode impedance for some of the models; that's something I've not seen on other balun manufacturers' web sites: http://www.balundesigns.com/servlet/the-98/i
Jim, Can you say something more about what you see as the failings of the AIM. I was impressed by how my AIM handled high impedances. If I calibrate it carefully, and then measure a 10k resistor, the
Jim, Instruments like the AIM attempt to "calibrate out" the fixture. You show the instrument a short-circuit, an open-circuit, and a known load, right at the measurement plane. It can then remove th
I tried a few more measurements this morning. I wound a choke on a FT240-61 core and measured its SRF using various methods. * I used the test set-up shown in Fig 40 of Jim's paper, but included a 10
Jim, Agreed - that's why I deliberately chose a choke wound on #61 material to do the measurements - the higher Q resulted in more pronounced shifts of SRF with stray C. Given the importance of havin
Joe, Have you actually seen the AIM produce SWR values less than 1:1, or are you critical of it simply because the scale has values below 1? If the latter, you'll be pleased to know that values below
Joe, * The user can't configure the bottom end of that scale, so that let's him off the hook. * You've never seen an AIM display values in that region and nor have I, so I don't think there's any rea
Jim, Thanks for that. Your explanation encouraged me to go and re-read your paper. As always it was a "good read". Did I see some significant changes from previous versions: 1) Earlier versions of th
Jim, Thanks for the clarification. As you say: "He who never made a mistake never made anything". I remain puzzled by what you just said about the flux in the cores of N:1 Current Baluns. Any analysi
Jim, Sorry, but I'm still going to disagree ;) Tom (W8JI) and Owen (VK1OD) have both shown that you can't create a 4:1 current balun by combining the two 1:1's on a common magnetic circuit. Two of th
Kevin, I'll risk further criticism of AIM measurements and point you to some charts on my web site which might make things clearer: http://www.karinya.net/g3txq/chokes/ Notice how narrow-band the res
Jim, This sketch may help: http://www.karinya.net/g3txq/temp/4%20to%201%20current%20balun%202.png I've re-drawn the usual 4:1 current balun schematic (Fig 1) into a different, but exact equivalent, s
Jim, Please see my last posting. The differential-mode input voltage is not just _between_ the windings of one balun, it is _across_ the windings. If there were no differential-mode transformer actio
I find some of the comments about commercial suppliers a bit odd. I'm not here to promote Balun Designs products - I have no connection with them - but if you take a look at the performance shown her
We shouldn't assume that just because an antenna is horizontal it produces only horizontally-polarized radiation. Take a look at a horizontal half-wave dipole with a modelling programme and you'll fi
Al, Main EZNEC window, click on Desc Options at the bottom. Select the "Vert, Horiz, Total" option in the "Fields" Tab. Then try some FF Plots. It's an eye opener! 73, Steve G3TXQ ___________________
No - it IS the polarization of the far field signal resolved as separate horizontal and vertical components. Take a look at the two components for a hexbeam as predicted by EZNEC: http://www.karinya.
I don't think you told us the element diameter. From EZNEC I see about 272ohms /500kHz for #20 wire, and 186ohms/500kHz with 1" diameter. Steve G3TXQ _______________________________________________ _
Where are you measuring the 26+j0 ? Unless it's right at the feedpoint with the antenna in its final position, that might explain your problem. 73, Steve G3TXQ _______________________________________
37 @ -45 degrees is the polar notation alternative form of 25-j25. Actually it's closer to 35@-45 degrees, but who's splitting hairs? 73, Steve G3TXQ _______________________________________________ _