After hams put up antennas, locate their shack, and run wires, the last thing they think about is lightning protection.  It should have been the first thing they thought about.  After you do all that, many have situations where adequate lightning protection cannot be installed without starting over and reconfiguring their station.  You could say that is expensive.   

If you plan the ground system before you install antennas and runs wires, usually the cost is not very expensive at all.  It used to be really cheap before the cost of copper went crazy.  Eight years ago, I think I spent about $270 on my grounding system with 11 ground rods, 200 ft #4 wire, and 15 single shots (before copper went crazy).  Most people don't need that much stuff, although individual items will be more expensive today.  A few ground rods and some ground wire is what you need, but most of the protection comes from the way you connect things together.  Yep, you can dream up a system where things can't be connected properly.  Don't do that.  And you can erect antennas that can't handle lightning strikes.  Don't do that, or don't put them next to your house (assuming you really want lightning protection).

Yes you can still get damage even if you have a good grounding system.  Lightning could miss your antenna and hit directly on your house.  If you live in an area of high probability of that, I suggest that you need lightning rods on your house.  Most people will just consider that to be a low risk item and ignore it.  A lightning protection system should be designed to protect the most valuable items, like your rig, antennas, and things inside the house.  It isn't worth the effort to try and protect small stuff, like a piece of coax, loading coil, Beverage antenna, or misc stuff like that since most of that has a low probability of getting damaged anyway and even if it does, the cost to replace it is low.

So lightning protection is not expensive, unless you didn't plan for it and end up with an antenna system that is impossible to protect.  The key to doing this correctly is knowing what to do, although I must admit that is sometimes difficult given the large amount of misinformation available on this subject.

Jerry, K4SAV

That's actually a true statement, but only because the "typical" ham antenna system isn't designed to handle a direct strike.  The "typical" ham antenna has very poor grounding, many with no grounding at all, many depending on a coax to be the major lightning current carrier, and a multitude of other problems that cause the system to fail.  Hams with good grounding systems are certainly in the minority, and are not typical.

See, you knew the answer already.  It might be the other way around.  Equipment that is disconnected close to the equipment is less likely to sustain damage.  It's easy to misinterpret what people say on this subject because many never state things clearly.  Like this thread for example, where people are talking about disconnecting equipment.  Many never say WHERE the disconnection is that they are talking about, and that makes a huge difference.

There are those, you notice, that think you will have damage from every lightning strike regardless of what you do and you can't prevent that.  That of course is totally false.  That may be due to their own personal experience of having a poor grounding system and not recognizing it.  There are many examples of surviving lightning strikes with no damage, including my own system, 2 to 3 direct strikes per year average for 8 years with no damage so far.  You can never get to zero probability of having damage but you can get to a low probability with a good grounding system.  For someone to say everyone will have damage with every strike is easily disproved.

Jerry, K4SAV

Disconnecting your equipment is not a substitute for good grounding.  If you don't have proper grounding you will probably have damage whether your rig is disconnected or not.  It might not be your rig that gets damaged but most everything else in your house.  Never disconnect coax or ground wires outside the house.  That just makes your grounding system not work properly.  If you want to disconnect your equipment inside the house, go for it.  If you don't have proper grounding, unhooking the cables outside the house isn't going to do much for protecting you.  That just allows lightning to choose whatever path it likes.

Jerry, K4SAV

Yep, it sure is.  That means you can't even put up a quarter wave vertical for any band under 12 meters.  Dipoles at 10 ft height will have lots of ground loss.  Considering the sag of a dipole, you can't even get it high enough to be out of reach for anyone walking under it.  UHF and VHF will be very difficult because you will have to shoot the signal thru every tree and building in the path and that's usually a lot of attenuation.  Your home station will work about the same as being mobile on VHF and UHF.  Obviously they don't care what PRB-1 says.

Jerry, K4SAV

It's going to be tricky.  There are several limits in EZNEC which can easily be exceeded with the model for this antenna.

1.  Always run the average gain test to see if the model is making errors.  There are a few reasons this can happen.

2.  You can't make lines intersect in the middle of a wire (usually).  Use separate wires.  Model the boom too if you use the gamma match and no transmission lines.

3.  The matching sections can be separated into 2 parts, the bar section near the elements and the center section connecting the bars on the two elements.  By using a transmission line to connect these two sections, instead of actual wires, that may make it easier to avoid some of the NEC errors. 

4.  Where there are two wires parallel to each other and close together (like the phasing lines) make the segments in the adjacent wires the same (same number of segments and adjacent segments have the same length).  Usually many segments are required for these wires.

5.  You will have problems with different diameter wires where they intersect, especially with short wires intersecting larger diameter wires that have many segments.  NEC doesn't handle intersection of different diameter wires very well.  You may not be able to get the error low enough with the actual diameter wires used in the antenna, and may have to resort to making the diameters closer to the same value.

You might be interested in reading this:
http://w4rnl.net46.net/hb.html

Jerry, K4SAV

There is nothing wrong with disconnecting your equipment during a storm but that is not a replacement for good grounding, which should all be outside your house.  If you don't have proper grounding outside the house and think that disconnecting the equipment will prevent damage you are in for a big surprise when the first strike occurs.

Jerry, K4SAV

Providing a good grounding system is actually much easier with a tower than with wire antennas.  The tower serves as the lightning path and with several ground rods, most of the current goes into the dirt at the base of the tower.  Some of it goes toward the house on the ground wire and coax lines.  A good common point ground connecting the ground from the tower and the AC ground at the house does the rest of the job, assuming all your antenna cables are also grounded to that point and you have no cables entering the house at other places.

With wire antennas there is a problem.  A coax line or ladderline will not handle a lightning strike.  They will disintegrate.  When that happens, there is no controlled path for the lightning and it will jump to any place that seems like a good ground.  That is usually multiple places on your house.  I have seen this and the results are nasty.

With a tower you can add inverted vee antennas on the tower and it's most likely (not guaranteed) that lightning will hit the higher tower and not the wires.   If the tower is not next to the house and neither are the wires, that offers a little lower probability of having damage if the wires do get hit.

Jerry, K4SAV

Beware of recommendations stating little or no grounding is required, then that person stating they have done that for years and never had a problem.  Invariably the reason they have never had a problem is because their antenna has never been hit by lightning.  If that person posts a lot, you can usually find other posts by that person and find them saying they have never had a lightning strike, but they won't tell you that when recommending their grounding approach.

Grounding for lightning protection should all be done OUTSIDE the house.  If you do that properly, you don't have to worry about grounding your rig.  It will have a ground connection by the coax and the AC plug anyway.  Run a ground wire to your rig if it makes you feel better but it isn't really necessary. 

The last thing you want to do is plan a system where the lightning current runs thru your house to the rig.  If you don't have lightning current running thru your rig, then there is no need for a big grounding cable run from the outside ground to the rig, and there is no need for an elaborate grounding panel behind the rig.  HOWEVER if you do that grounding outside incorrectly, the lightning current WILL go thru your house regardless of what the grounding is behind the rig, and you will probably have major damage.

Notice that with proper grounding outside, there is no requirement that the station be located anywhere in particular inside the house.  Second floor is fine.  My station is on the second floor and I have a 45 ft run inside the house to the entrance panel which is located on a wall next to the AC power entrance panel.  My tower gets hit 2 to 3 times per year average and no damage so far (since putting the tower up 8 years ago), but I also have a good grounding system outside the house.

Jerry, K4SAV

Here are the recommendations from the ARRL Handbook

Spacing 
inches ___ V_peak 
0.015 ___ 1000
0.02 ____ 1200
0.03 ____ 1500
0.05 ____ 2000
0.07 ____ 3000
0.08 ____ 3500
0.125 ___ 4500
0.15 ____ 6000
0.175 ___ 7000
0.25 ____ 9000
0.35 ___ 11000
0.5 ____ 13000

Glad to hear the vertical is working well for you.  As you are finding out, you learn a lot more when you build your own antennas. 

As for performance, it varies with location, and when compared to a dipole it varies with dipole height, direction, and arrival angle of the signal.  Many people have lots of noise on verticals because they receive the low angle noise signals from a city.  My experience, as yours, is that the vertical usually has a better signal to noise ratio for DX compared to as low dipole, but I don't have city noise. 

The arrival angle of the signal make a big difference.  Most of the vertical's signal is concentrated at low angles while most of the signal from a low dipole are at high angles.  So the dipole may be better for close signals and the vertical better for DX.  If the dipole is very high, then you may find that it is better than the vertical for DX.  Also the direction of signal arrival makes a big difference.  The dipole has lobes and nulls, the vertical doesn't, so the results will depend on which direction the signal comes from. 

These are some of the reasons people say you can never have too many antennas.  You may also find that transmitting on one antenna and listening on the other may provide some advantages.

Jerry, K4SAV

How directional the antenna is depends on the elevation angle.  If you only look at 90 degrees elevation, NO antenna is directional.  A 102 ft dipole at 25 ft height and at 15 degrees elevation should have a MAXIMUM ratio of lobes to nulls of about the following:

80 - 3.5 dB
75 - 4.5 dB
40 - 12.5 dB
20 - 18 dB
15 - 27 dB
10 - 37 dB

As PA1ZP said, other things effect the nulls.  Surrounding objects, drooping wires, antenna asymmetry, common mode currents. etc all tend to fill in the nulls.  If you account for those things in the model, then the model will show the results.  In the real world it is highly unlikely that you will ever see that 37 dB ratio on 10 meters or the 27 dB on 15 meters, but what you will see will be a large difference.

 Jerry, K4SAV

I looked back thru my old EZNEC files, and yes it is there, several versions, including his original file. 

The short summary is: stay away from the off-center fed version.  In that version, the feedline does most of the radiating, so the gain will depend on the feedline length and how it is routed.  A feedline near the ground will work like a dipole on the ground. 

The center fed version isn't too bad (if your reference is a typical radial-less vertical), except on 80 meters.  The SWR on 80 is huge and even open wire line will have a lot of loss.  Over average ground the gain on 3.5 MHz using 100 ft of Wireman 551 ladderline is about -11.7 dBi.  On 40M the gain increases to about -2.7 dBi.  On 20M, it's about -2.7 dBi.  On 15M, gain is about 0 dBi.  On 10M, gain is about 1.7 dBi.  All those numbers are with 100 ft of Wireman 551 ladderline.  You should be able to do a little better if you build your own low loss open wire line.

Jerry, K4SAV

A half square acts a two phased verticals.  For the antenna to act like a half square, the current in the vertical elements needs to be in phase.  Since the feedpoint of the antenna is unbalanced, to keep the currents going to the elements at the right phase, and not down the coax shield, a good choke is required.  The position of the feedline has to be carefully routed to keep from interacting with the antenna.

When you try to feed it with ladder line you have the same requirements.  I haven't tried this, but I guess you could use a 4 to 1 current mode balun located at the antenna feedpoint with the 50 ohm side connected to the antenna.

250 ft is not a long distance for a feedline on 40 meters.  RG213 with a matched load should have less than a half dB loss.  If you are planning to use this antenna on multiple bands, it will only look like a half square on one band.  It will perform poorly on bands other than 40 meters.

The half square can also be fed at the bottom of a vertical element.  It will be a high impedance at that point, and you will need some radials.  You will need a matching network and maybe a choke on the feedline.

Jerry, K4SAV

edit:
I read the attenuation of RG213 incorrectly.  It's about 1.2 dB per 250 ft with a matched load.

I remember seeing pictures of that antenna used by one of the DXpeditions.  I thought that was a great idea for a DXpedition.  It's essentially three phased verticals, each vertical element has two radials, and the whole thing is mounted on a boom so that it can be rotated.   Put that over salt water at low heights and you have a killer antenna.  Put it over dirt at low heights and it can be easily be beaten by a dipole.

Jerry, K4SAV