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[W5DXP]

Thanks for info Cecil. I read an article last night of a Bobtail beam made with a reflector duplicate antenna spaced behind the driven antenna bout .25 wavelength and with verticals cut 6% longer.

Note that a "duplicate antenna" is never 1/4WL long. A "duplicate antenna" reflector for a half-square is one wavelength long which IS resonant.

[W9IQ]

If we are drawing a fine line under this point, neither a director nor reflector are typically resonant. The reflector is physically longer than the driven element and any directors. The directors are physically shorter than the driven element and the reflector. Clearly two of the three, at a minimum, are not resonant.

- Glenn W9IQ

[K4SAV]

Cebik wrote about the two element and 3 element half squares which I printed out and save some years back. He designed for two meters. The two element had a gain of 13 dBI with front to back of 18 dB.

You can get a front to back of 18 dB (and even more) out of a 20 meter two element half square, and you can get a gain of 13 dBi out of it over salt water.  If you put it over average ground the gain will drop to about 6.7 dBi (with the top wire at 30 ft), which is about 1 dB less than a half wave dipole at 50 ft.  By increasing the height by another 20 or 30 feet you might get another dB out of it.

Jerry, K4SAV

[W5DXP]

If we are drawing a fine line under this point, neither a director nor reflector are typically resonant.

True, but my point is that properly functioning directors and reflectors are close to resonance and experience resonance effects, i.e. high current and voltage.

[W1VT]

A drone with a field strength meter and GPS/altimeter would be very useful in adjusting that reflector and director.  Just tweak the parasitic elements for the best pattern and call it done!

Zack W1VT

[W9IQ]

Cecil,

True, but my point is that properly functioning directors and reflectors are close to resonance and experience resonance effects

I am not doubting you, I am just sensitive to the ham community regularily abusing the term "resonant".

- Glenn W9IQ

[K4RVN]

Zack, I will be using a field strength meter but no drone. My plan is to use the FS meter before I put the reflector and director up.
I will record the field strengths broadside. Then after putting the reflector and director up, I will take the readings again to see if there is a change. In my view, the antenna should be throwing less power off the back beyond the reflector and more in the director direction if the parasitics are working. That is a great idea you suggested but I cannot fly a drone and have no friends who do that.
BTW, I am 300 miles from salt water so plan to put a few radials down since I have no idea of the soil conductivity. It is written that this antenna does not have to have a great ground but I have the space and wire to install some radials plus a ground rod. I have a roll of galvanized fence wire left over from my beverage antenna project for 40 meters. It should be Ok for a few years buried about 2 inches so I can bush hog over it.

Frank

[WB6BYU]

BTW, I am 300 miles from salt water so plan to put a few radials down since I have no idea of the soil conductivity. It is written that this antenna does not have to have a great ground but I have the space and wire to install some radials plus a ground rod...

The improvement from adding radials under the antenna, and the effect of ground conductivity on signal strengths
at low angles, are actually different mechanisms.

Radials reduce the ground loss in the immediate vicinity of the antenna.  Because the feedpoint impedance is
high, this won't make as big of a difference as it can with a quarter wave vertical.  20 ohms of ground loss makes
a much larger difference with a 30 ohm antenna than with a 2000 ohm antenna.

The effect on radiation is due to the phase of the ground reflection out to 50 or 100 wavelengths from the antenna,
much further than most hams will run radials.  With good conductivity you get better low angle radiation, while with
poor soil you may find that a vertical is no better than a half wave horizontal dipole hung from the same supports.

[W5DXP]

I am just sensitive to the ham community regularily abusing the term "resonant".

Please allow me to amend my earlier statement. Passive reflectors and directors must experience resonance effects for them to function properly even though they exhibit a small amount of reactance and are therefore, strictly speaking, not resonant. How's that? 

[W9IQ]

Ahem. I think 'nearly resonant' or 'slightly off resonance' would be close enough...

- Glenn W9IQ

[WB6BYU]

And it gets even more confusing than that:  the reflector in a yagi may be self-resonant at the
operating frequency when the other elements are removed, and the driven element may be resonant
at a higher frequency that is out of band.  So you have to be very careful in your definition of
"resonant" and under what conditions you measure it.

[W9IQ]

I think the term "in situ" would apply here.

- Glenn W9IQ

[KM1H]

I think it would be better to drop the nitpicking BS and actually "try" to help the OP.......

[WZ7U]

I think it would be better to drop the nitpicking BS and actually "try" to help the OP.......

And ^this^ does that how? 

[K4RVN]

I have built my tuning network for the Bobtail curtain so that I can voltage feed the center vertical. Quite a learning task to wind a coil, assemble the surplus variable capacitor and bench tune the unit. I followed the instructions in an article by Greg, VE3NXB  and wired a 4k ohm resistor across the coil for a dummy load to match the feedpoint impedance of about 4000 ohms. Using the article I was able to make sure the unit works as intended so far. I am waiting for a little cooler weather and the ticks and chiggers to die off before installing the antenna. Like some have said this antenna is very narrow banded, and may not work out but I have kept the brain circuits energized. It will be fun to see if a single vertical of 1/2 wave length added in front and behind the center antenna 1/4
wave vertical will act as a director and reflector as stated in the MFJ article on the internet. I bought an inductance meter off the net
for the project for about 30 bucks. It will be useful later perhaps so I don't mind adding it to my instruments.

Frank