Can this be used as client? Jeff? Anyone?

Here's what was actually built:

Note that the W9CF Yagi java applet modelling program does not design or optimize the antenna. It just calculates what is possible.

Note the calculated gain is 15.53dBi for a 15 element yagi. This is best case as reality is usually somewhat less. Incidentally, I don't see a VSWR vs frequency plot on this design. There's more to making an antenna work than just gain.

That's normal for a yagi that tries to get a 50 or 75 ohm match from a folded dipole driven element without an additional matching xfomer. The first director usually ends up fairly close to the driven element. The 2nd and 3rd are also closely spaced. After those, the element spacing is almost equally spaced. No waviness anywhere that I can see.

If you look the the examples, there's the NBS 15 element 2 meter (144 mhz) Yagi, which has "almost" equally spaced directors.

Reply to
Jeff Liebermann
Loading thread data ...

Thanks Jeff.

Looks like it's just sloppy construction as you suggested.

With that cheap yagi you bought, is there any way you could easily convert it to folded dipole?

Reply to
Dr Who

Yes, I was thinking of the same thing. One way would be to buy the version of the Yagi with the folded dipole driven element, but that's too easy. It might be possible to build a folded dipole using flat copper wire exactly like the MFJ-1800 driven element.

There's a catch. The resultant antenna ended up with a 200 ohm drive impedance, instead of 50 ohms. However, a 2:1 balun is easy enough to build. I usually use semi-rigid coax cable for the balun. See balun details at:

One potentially expensive problem is that you're going to need some test equipment to determine if it's correctly tuned and positioned. Besides the usual "tune for maximum" gain adjustments, there's also minimizing the VSWR.

I use a reflection coefficient bridge, RF sweep generator, and oscilloscope.

Reply to
Jeff Liebermann

When you start delving into this subject is show how much there is to it.

Plenty to learn.

And some pretty smart people out there.

Interesting links.



Reply to
Dr Who Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.