Magic is simply a lack of understanding of what's really going on.VK2XTC wrote:It seems that making antennas is more "magic" than science.
Antenna design is a science, it's just not one you can conquer in a day of learning. Likewise, baluns. Types of balun (voltage vs current balun), ferrite choice, etc. It's a complex area. This is a technical hobby. You can't dominate it overnight but that's what makes it interesting.
As for 468/f vs 300/f. The wavelength of light in feet is 984/f, half wavelength being 492/f. In metres it's 300/f. Those two values are equivalent. 468 is about 5% too short, but there are reasons for that.
Antennas are affected by all sorts of things, like whether the wire is insulated or bare copper (insulated has a slightly lower velocity factor, and your antenna can be a few percent shorter) and how you have supported it at the ends (it's possible to add a bit of capacitance here and affect the overall tuning).
You would be better off with a 4:1 current mode balun. However, if you keep your existing voltage balun then adding a choke right where the coax goes into the balun will help.Lastly, Common Mode Currents. Seems I need an RF Choke for this antenna.
Now, you also mentioned you're using stainless steel. Stainless steel has significantly lower conductivity than copper and sometimes has some ferromagnetic qualities too, which both affect how RF travels in it. So if you follow an antenna design that was done using copper and use exactly the same dimensions in stainless steel, it may not work. Stainless steel has a higher effective impedance at RF and this can throw off your antenna design significantly. Particularly for low-impedance antennas like centre fed dipoles it can ruin your day. An OCF is fed typically at the 300 ohm point (not the 72 ohm point as with a centre-fed dipole) and so the higher impedance of steel may not matter as much.
Here's a report on Steel vs Copper in antenna wires.
It's a self-learning hobby. One would hope that by playing with bits of wire you eventually end up with a competent understanding about how RF 'works'. Do you know how your smart phone works? Or your computer? I mean really understand how it works. How does the BIOS work? How does the disk controller get the data off a spinning disc of metal? Or how does WiFi manage to get data transferred without the bits and bytes from your neighbours smashing into each other in the sky? Having technology available is nice, but if you don't understand it in intricate detail then you can't fix it if it breaks. You are dependent on someone else who does understand it. If you just sit around and play Facebook on your smart phone then you are a slave to it. With AR, it's simple enough that you do have a hope of figuring out how to squirt RF into the sky. And hopefully you manage to do it safely too.VK4WDM wrote:I find it fascinating that even with all the complex technology available to us, many hams still have great fun messing around with pieces of wire.
