My 4 Square Summary!

Attention: nobody is perfect, there might be mistakes. Thanks for an email with corrections,This page was created to note important facts concerning 4 squares. I read a lot, but I also forget a lot.
So I started to write down "all about 4 sqaures" to remember me from time to time. Please read ON4UNs book and other sources to lear all about 4 squares.
I try to add links to other great 4 square articles on the web.

1. A (classical) 4 square consists of 4 quarterwave long verticals, spaced a quarter wave in a four corner arrangement.
300.000/3650khz = 82,2m wavelength / 4 = 20,60m = quarterwave
diagonal/Across = a^2+b^2=c^2 -> sqrt(a^2+b^2) = 29m across or 14,5m radius

2. All elements are fed at the same time, (with different phase angles)

3. it fires a) through the corners ( 1 leading element + 1 lagging element + 2 emlement combined as "a fat element" in the middle or b) "broadside ( 2x2 arrangement, 2 pairs of phased verticals)

4."classical" phase angles are -90 degrees (lagging), zero degrees (the two elementin the middle) and +90 degrees (leading). Hybrid - this is was Comtek offers.

5. for better/best performance you may build your own phasing network to adjust phasing angles to a maximum forward gain or front to back or a combination. att: you may need a more complex switching unit
because the beamwidth is now narrower than 90 degrees Remember, that more components can cause more faillures. One who has an excellent setup with great success is Paul. Look at PA0GMWs 4 square, which is in my opinion the best developed one in EU (individual phase angles, plus terriffic QTH (salt march land, good ground, flat terrain)

6. The network/hybrid is located in the center of the square

7. The feedlines to the verticals

You can use 50 Ohm or 75 Ohm cables for the feedlines. As far as I understand, it is better to use 75 Ohm cables, but 50 Ohm cables will also work. At another site was said, use 50 Ohm when ground radials, use 75Ohm when elevated radials are used. You need a current balun to prevent the coax from radiating when you are using elevated feed points!!!

There are 4 feedlines to the 4 verticals. (all fed array) with a length of 90 degrees / quarterwave.
ATTENTION you need this in ELECTRICAL length, not mechanical! So do not forget the VELOCITY FACTOR of the Coax. 300.000 / 3650khz = 82,2m / 4 = 20,60m * VF(velocity factor) = ?
RG213, RG58 and RG59 mostly have 0.66 VF. so the cables are 20,60m * 0,66 = 13,60m long. oooops, that is TOO short. you will not reach the verticals (see fig. 1 where the radius is 14,50m!)

You need another coax e.g.: Aircell7, compare:

OR

Ich you have no chance to get Aircell7 or want to use the very cheap RG59 or RG58, you may use
3*quarterwave lambda cables which is 300.000/3650=82,2/4=20,60*3= 61,80m * 0,66velocity factor = 40,8m long cables (you need 4 of them, one for each vertical)

The best choice (quality) would be Aircell7 rather than using a very long coax (3 wavelength RG58/RG59/RG213). If you want the last fraction of a db, go for a cable with 0,8x velocity factor.
For some reasons you might want to use "longer" cable. In my case, I can hide the cable better and my garden ( which belongs to my hotel) looks a little nicer.

For cutting the right length, please calculate the cable length PLUS about 2m more and then measure properly.
However, when I calculated and then measured the cable I always came very close to the calculated length.

YOU NEED FERRITE CORES on the feedlines at the 4 verticals to let the radial and vertical resonate and NOT the feedline! (current balun)

8. The Verticals

there are many different types of antennas forms you can use. Classical and best is a fullsize vertical which is 20,60m tall (for 80m). It can be a freestanding or guyed aluminium pole or a wire attached to a tree. you may use sloping verticals hung from a tower (the more vertical the wires are, the better the performance). you can use loaded verticals, the must not be fullsize! It depends on the loading form how effective the system will work. Try to avoid base coil loading! That has the most losses. Try to use top loading, like an inverted L. Use centerloading with coils with a Q of 200,300 or even better. I use center coil loading at my 80m 4 square. If the Q is good enough, there is not too much disadvantage towards Inverted L loading. If you want the last fraction of a db and can not use fullsize elements, use Inverted L elements or even better T elements because then the high angle radiation of the horizontal wire will be cancelled out.
"Fat" aluminium poles are better (broadbander) than thinner copper wire verticals. But they are more expensive and takes longer to construct.
You can NOT use grounded towers with omega or gamma match. This will not work! (or at least you will get mad before you get the phase angles right,)
When you build your vertical, try to build them all the same dimensions! Same length, same loading, same coils etc! Later you can fine tune the resonance frequency with the length of the radials. Also CW/SSB band part switching is done by inserting a biece of wire or coil IN the radial.

9. The Radials
Maximum performance: use 120 quarterwave long radials, under EACH vertical. This is what is tested and calculated the "best" ground. Use broad bus wires to connect radials, where they cross each other.
A 4 square will work also with less (ground) radials. Remember: the better the ground the fewer radials are neccessary to get maximum performance.
for temporary use or where ground radials are not possible, one may try with elevated radials. The simplest way is 1 radial per vertical installed "outwards" from the array. Raised 2-6m (80m array). ON4UN has installed his 4 square ABOVE the radial field of his 160m vertical. When you live near the sea or can install your 4 sqaure right at the beach you will not need more than just a single elevated radial.

Elevated radials must be resonant. Ground radials must NOT be resonant.
You may even use loaded/shortened elevated radials! Use let's say 4 short radials ( some say, up to two-thirds is no big difference to fullsize) per vertical and use ONE coil (with high Q) per vertical to get them to resonate at 3650MHz.
I have the problem, that I can not install radials on ground and not elevated radials that run outwards the array. The big problem in my case is: How do I build my radials:

They shall not interact with other radials --- symmetrically, so they cancel the high radiation out
They must be loaded the most effective way if not fullsize --- good coil, or endloading (like a laying L or T)
They must be "symetrical" ---- the only way to get this is to use the space INSIDE the array

haveing enough space, it is not a big deal to build a 4 square nowadays.....you may order everything plug&play from www.dxengineering.com (Comtekboxes) if you are satisfied with -90-0+90 angles and "standard" gain...
.if you want a killer 4 square like PA0GMW and others, you will have to build your own phase network with 8 directions and: you need excellent ground and terrain and no neighbours.

important Links with 4 square topics