Twin coax is _not_ always a good, or even a fair, substitute for open-wire line. Here's an illustration of how bad it could be. The driving-point impedance of my quasi-G5RV doublet for f = 10.1 MHz i
What I did when I installed this antenna was to run 15 meters of open-wire line to the end of my house nearest the antenna, then go through the wall up near the peak of the roof with a pair of big St
Yes, but I bet your model did not (properly) include the _feedline_. Unless this feedline is _seriously_ loaded with common-mode chokes, it carries substantial common-mode current, which not only rad
I remember this, too; and it remains true today; doesn't it? I don't remember hearing about an open-air coil outside the house; and, anyway, an open-air coil outside seems to me a bad idea. It'd be u
You were within the "near field" region, where the antenna's radiation field is dominated by its quasi-static field. Here, the amplitude of the (oscillating) electric field is approximately that of a
What are the wall thicknesses of the tubing in the elements of a Force 12 C-4XL, for * the standard, 80-mph, model; * the "D," 100-mph, model; * the "H," 120-mph, model; and/or * the "HH," 140-mph, m
What is "the standard wall"? For zero clearance, it'd be 1/16th inch, or 0.0625". So, is 0.058, which would leave 0.0045", the standard? (I guess.) -C.
Yes. As SWR changes, the ratio of reverse (reflected) power to forward power changes. So does the ratio of the _net_ forward power (i.e., the forward power minus the reverse power), to the forward po
It depends on the "impedance" (i.e., the ratio of the voltage to the current) of the common-mode wave at the point on the common-mode transmission line where you insert the choke. (I put "impedance"
I never said that it did. However, when you insert a choke at one point along the line, the common-mode-wave reflection from this choke causes a current minimum to appear there, so a current maximum
Every week I check into a vintage military radio net in which most stations are transmitting about 10 W. In the last session of this net, propagation was very poor, QRN from thunderstorms was high, a
Actually, I have three RF current probes that I've used for this purpose. All are broadband; one uses a snap-around ferrite toroidal core; one uses a continuous ferrite toroidal core [so you must thr
"Last year a bought and measured the Radio Works Line Isolator in my in line (isolation on the outer shield) balun test setup using an HP Network Analyzer. It measured about 220 Ohm at 1.8 MHz and 50
How about _impedance_?! It can't be much, with a single "turn" through so little ferrite. For what band(s) are they advertising this product? HF? VHF? -Chuck, W1HIS
The Force 12 baluns and the 50 small beads _are_ common-mode chokes. I don't know how much choking impedance they provide; but, in conjunction with the capacitance to ground of your 125 feet of burie
For those of us who haven't saved our magazines from 1978, can you please give us the vital stat's of your broad band toroid balun design? What material? What size toroid(s)? How many turns of what?
An appendix of the RSGB book on EMC teaches this style of winding. Excellent choice. I've used Fair-Rite type 61 in my baluns and un-uns, too. It has very low loss so it won't get hot at high power a
...to which I replied, "I'll measure one and report back." I just wound a "W1JR Balun" as specified, using an FT-240-61 toroid and RG-303; then I measured its common-mode impedance (between the ends
If I had separate feedlines for high and low bands, I would indeed use differently-designed common-mode chokes. I'd probably use FT-240-61 toroids in both; and, to determine the numbers of turns to u