The Infernal Tower

Make sure that any loose paint and rust is wire brushed off your tower and that any rusty area is painted. I recommend a metal rust paint such as Tremclad. I used 3 litres – 2 white and 1 grey (mix to your own preference) and had some left over. All the rivets must be secure or replaced with a tight fitting machine screw and lock washer.

When I first tackled this job, my ham scrounging showed through and I figured that I might use regular 1/2" bolts, washers and nuts and channel steel for legs – and I probably could have… but … common sense prevailed and I bought the right stuff. Be sure to obtain the proper tower bolts for your tower. In the case of my Delhi 48 – these are a very solid looking tapered shoulder bolt with an inside star washer for the hex nut side. Similarly, don't scrimp, buy the correct galvanized steel tower legs for your tower. The prices are unreasonable, but in the long run worth it.

For your information and frustration, the Delhi tower people, located near Delhi, Ontario, just east of London, recently sold their tower manufacturing plant to Taco Antenna and their phone number is 1 800 463-1607, but they only sell to dealers. You can phone them and get the dealer nearest you.

Inspect your tower carefully – you want it to stay up there for at least 12 years! If any bolt holes are elongated, you must attach backing plates to reinforce your tower attachment at this point. In my situation, my section 7 to 6 joint (my sections number from the bottom starting at #8) was elongated slightly. I bought a piece of 1/8" steel strapping, 1" wide and 4 feet long and made 3 plates (one for each leg) and drilled them on a drill press carefully, with 4 holes. 2 aligned with the original holes, and 2 new holes above and below the joint. (Don't cut the pieces off until all holes are drilled - safer and easier on the drill press) I did not use a tapered shoulder bolt in these extra holes but I did use a straight shoulder bolt and lock washer.

Be sure that your mast bearing and rotator will mount with the proper size bolts. Everything must work smoothly by finger, because when you are at the top of the tower, you don't want to mess around with rough running threads. I mounted my bearing ahead of time and made sure that it was exactly in the centre.

I went to a local scrap dealer and bought a thick-walled, 2" aluminum 12' pipe for $2 per pound. It weighed about 10 pounds. What a bargain! It's slightly less than 2" diameter but close enough for the weight that I'm putting on it. The mast should extend down into the tower through a well-greased mast bearing, which can be adjusted to centre the pipe. The further down into the tower the mast goes, the less stress on the rotator, etc. I'm not sure what the ideal arrangement is, but mine is a 12' mast 6' above the tower and 6 feet down into the tower. It might be nice to have a mast all the way down to the base of the tower, but there are complications doing this, including consideration for the weight of the pipe downward onto the rotator, and also the need for intermediate mast bearings. This might also result in some backlash when rotating the antenna. Anyway, my mast extends 6' into the tower.

I have a Delhi MMB bearing which was kindly provided with my tower. Gord (VE3KKL) explained to me how to remove the little plug in the side of the bearing. I ground off the metal burrs holding the plug, then carefully drilled a small hole in the middle of the plug. I screwed a tiny self-tap screw into that hole, and was able to use that as a handle to remove the plug. If you try this, be carefull not to lose any of the ball bearings. They are very loosely packed in there. I applied a grease nipple, mounted in a stainless clamp, over the ball bearing access hole, and lightly tightened this assembly into place. I charged my old grease gun with heavy duty grease and pumped as much grease as I could get into the bearing, while I kept rotating it a bit at a time. After I was sure that it was well-greased, I removed the clamp and grease nipple and put the original plug back over the hole. I kept this in place with a piece of black vinyl tape, held in place by a stainless steel hose clamp.

There are plenty of reasonably priced rotators available used on the swap shops. Mine was a Yaesu G400R with a very attractive display, and I only paid $75 for it. But when I bought it, I knew that I had to find a new mast clamp bracket for it. A new Yaesu bracket kit cost me $45, so for about $125 I ended up with a good reconditioned rotator with new bolts as well. Remember to find some rotator cable. This should be vinyl jacketed, and have enough conductors to work with your rotator. Be sure to use stranded wire of a gauge suitable for the distance from your shack to the rotator.

We spent a good deal of time choosing the site. Things like distance from the shack, surrounding obstacles, soil and terrain are all important factors. If the tower is going to be close to the house, remember to allow for your roof over hang, unless you want to do some messy and expensive home renovations later. Also, keep in mind, if you are putting the tower near the house and have a block foundation wall, don't get too close to the wall, or you will have to use forms, or risk about 10,000 pounds of wet concrete in your basement.

The recommended minimum size of the hole for a Delhi 48 foot heavy duty tower is about 4' x 4' x 4'. The hole must extend down below the frost line. If the tower will be close to the house, this is not usually a problem because enough heat escapes from the foundation to keep the frost level not too deep. Be sure to wheel the soil away, or it will be in the way while you are working or when the base is being poured.

We marked the hole with pegs and with a string – this may seem unnecessary but it helps you keep things square. We dug the hole by hand. In my case the hole was located about 2 feet from my house's poured-wall foundation. There was a good reason for this. The home is located on very rocky terrain. I knew that there was sand for the first 4 to 8 feet around the house, going down to the footings. As we dug the hole, we hit rock on the side of the hole farthest from the house. Unfortunately we hit the rock at about the 2 foot mark and it was very tough digging from there. Once you are down in the hole, you cannot use a long handled shovel, so the soil has to be tossed pretty high with a short handled shovel, to hit a wheel barrow standing somewhere above the hole. My strong 15 year old son, was wishing that he was a foot taller. We broke and loosened the rock with a long, heavy, pointed steel bar. Then we took very small quantities of soil and rock at each throw. Also, a lot of the earth and rock was lifted out via pail – all in all a tough job that took about 5 hours of hard labour. If not for the rock, we would have been done in about 2 hours.

Decide whether you want the tower base to be below the grade and covered with sod, at grade, or above the grade. Keep in mind that this could become a selling issue for your house later, if the potential owners don't happen to want a large concrete mass sticking out of the lawn. My concrete base ended up about 5 inches below grade – which will hopefully allow sod to survive over it.

This may seem obvious to some of you, but you must place the tower with the legs firmly bolted onto it, into the hole, prior to pouring. Be sure to put bolts or threaded rods through the holes at the bottom of the tower legs. This helps anchor the legs permanently in the concrete.

This took a while to figure out. What I eventually did was build a sort of wooden cradle from 2" x 4" x 8'. I threaded this through the tower's steel cross bracing (see photos). I elevated the cradle and tower, using 2" x 2" x 3' wooden stakes and combinations of boards and wedges to make fine adjustments. Remember that things will move while the concrete is being poured. It is not easy to totally imobilize your tower against the weight of pouring concrete. Just make sure that you arrange things so that you can quickly and easily bring the tower back on course. I used all sorts of pencil marks, etc. and I am proud to say that my tower is perfectly straight but I must have checked it a hundred times. I used an extra long spirit level to keep the tower square. My tower does not have a continuous taper, like the new Delhi's, so it was quite easy. If you have one of the new continuous taper towers, find a trick that works for your tower. One idea that I heard was to use a particular diameter drill bit as a spacer to keep your level out the correct distance. I suggest that you fasten this in place somehow, so that there will be a minimum of fiddling while you are working with the concrete. Don't be afraid to put a few pencil marks and notes on your tower. Measure everything several times and watch out for Murphy.

There is a lot to know about concrete. I asked a lot of people a lot of questions and concluded that I knew nothing about this area of things. I was told that I should get between a 3500 pound and 5000 pound concrete.

A visitor to this site, John Florian, advises that the concrete numbers 3500 and 5000 refer to the concrete compressive strength in pounds per square inch. 5000 psi has a higher compressive strength and is therefore more resistant to freeze-thaw cycles than 3000 psi. The metric equivalent to 5000 psi is 32.5MPa (Mega-kilonewtons per square metre). Ask also for 6% air entrainment (adds about $10/cu m to the mix cost) to improve freeze-thaw resistance.

I got 5000 pound concrete because the concrete supplier did not charge extra for this, but did charge travel, so what the heck, go for the heavy stuff. If its cool when you are pouring, with a risk of freezing, you may need calcium in the concrete, but use with caution as it accelerates corrosion of the metal legs (according to the concrete man). If it is cold at night, be sure to cover the concrete with straw, and a tarp to keep the rain off for the first night or two. Make sure that your tower does not move for at least 48 hours, and continue being careful, for at least 1 week. When your tower base is poured, try to arrange to have a crown in the middle of the concrete, or at least a small trough in the concrete to drain away the water that settles on the top. If you forget this, phone the concrete contractor to come and cut a couple of ½" deep slits from the centre to the outside to allow drainage. This probably isn't necessary but I noticed that water was puddling in the middle of the base and I reasoned that this may be a problem later – not sure. Capillary action of the sod on top of this area probably is just as good. It was a cool day when my concrete was poured, about 15 degrees C, and it was soft enough to scratch our initials in it after 4 hours, probably longer.

If your concrete base is below grade, you will need to place some sort of protector around the tower legs to keep the soil away from the metal. The soil would otherwise hold the moisture in contact with the metal legs and promote corrosion. I thought about using 3 inch ABS pipe, slit in half then taped around each tower leg. I should have taped 8 inch cuffs of ABS up high on the leg prior to the pour but I didn't. I could have unbolted the tower to place the cuffs, but I didn't do that either. I suspect my thick layer of vinyl friction tape is good enough.

We considered all sorts of methods of getting concrete into the hole:

Mixing by Hand

There are several possibilities here ranging from ordering gravel, sand, and bags of dry cement and using a gas or electric mixer, to buying bags of concrete mix.

The problems with this include:

• hard work to mix a couple of cubic yards of concrete.
• Hard to get an even mix
• Hard to pour all the concrete in a reasonable time to get even curing

Delivery by Cement Truck

There are multiple choices here. You can have a truck of ready mix arrive, or you can order the type of truck that mixes exactly what you need at your site. Prices vary a bit but about $100 per cubic yard is typical and you can expect to pay extra for delivery and for waiting.

The problems with this include

• could not bring cement down our driveway and across lawn due to weight (many thousand pounds).
• wheeling by wheelbarrow from roadway was possible but would have required several helpers and an extra waiting time by cement truck.
• wheeling by wheelbarrow from road was about 200 feet. Lots of opportunity for accidental spills. And a lot of slugging. Concrete weighs between 110 pounds and 156 pounds per cubic foot. That's a lot!

Delivery by Tow Cart

This method has a lot of appeal in some locations and installations. The open-topped cart holds 1 cubic yard or less. That's thousands of pounds. The cart has only 2 wheels not 4 and does not have electric brakes. The cart has a dump hole at the rear with a lever operated steel trap door. The cart takes a 1 7/8" or 2" ball hitch and can be towed by a gutsy truck. The wire connection is a flat four connector.

Problems with this approach include:

• Cart too heavy for lawn
• Difficult to tow cart across lawn and back
• Dangerous to tow cart with anything less than a robust large pickup truck
• This is a very workable solution if you are near the supplier and have access to a heavy truck
• See Sources of Stuff for where you can get this. These folks are not particularly helpful or friendly.

Contracting Out - This was my preferred solution

I found a guy who was a part time concrete contractor. He co-ordinated the entire job, and just let me know the time. Great! He arrived with a gasoline powered, 4 wheel, cement wheelbarrow with a special pouring spout. He had a helper with him. They both knew what they were doing. There was zero waste, zero mess, zero damage. They are not cheap – he cost me $350 not including the concrete. He was on site for less than an hour. Easily worth the price in my situation. You have to maintain square of the tower yourself, between pours. His idea of perfectly square and mine differed somewhat, but that was fine, I kept trimming things up and made sure that the tower stayed centred in the hole – this is important. The contractor and his helper were very co-operative and helpful and let me do my squaring thing while they did theirs. They even brought a bale of straw to cover the concrete at night.

Grounding is important! The object of the exercise is to provide a drain, away from the concrete base for the lightning, if your tower is struck. We wouldn't want to split that nice big mass of concrete. Nor do we want to make it easy for any lightning to enter the shack. My solid copper alloy ground rods started as 10' long. They are quite expensive and very heavy. Be sure to buy the proper heavy duty bronze clamps for this job. It simplifies the job and gives a good connection. The more ground rods the better and I suggest not less than 3 full length ground rods properly fed and bonded.. I placed a ground rod on each side of the tower, about 6 feet away, and not close to the foundation. I used a very heavy gauge of copper ground wire. Its stiff and a bit heavy and little tough to work with. I buried the wire at shovel depth, from the ground rod to the tower leg, by prying open the ground then forcing the wire down into the crack and then stomping it down. I purchased copper ground lugs which take a ¼" bolt, from Canadian Tire automotive section. These copper lugs are labeled as Gauge #1 and come 2 to a box. I crimped these on to the tower end of my ground wire then soldered them with a small plumbing torch and radio-type resin core solder. First I attached the ground wire to each tower leg, using a tie-wrap. Then I cut the wire to the right length and attached the connector. Then I drilled a ¼" hole in the tower leg, and used a grinding disk to remove the paint from the tower leg at that point. I then used ¼" bolts with lock washers, to attach the lugs to the tower.

I live in the country so I have a good (domestic) grounding system off my 2 wells (the well casing goes down 20 feet). There are two ground rods used by the power system. The wells are connected to the house electrical system by a large diameter multi-strand copper cable about 6 feet below ground level. The house ground is a long way from the shack so I ran a separate ground into my shack through a separate entry point, not alongside the antenna cables. I have attached the shack ground to the house ground and the tower ground.

NOTE: For more info on grounding, please see the link at the bottom of this web page.

I looked at a lot of cable before ordering mine. I ended up buying a 500 foot reel of 9914. This is a low loss, multi-sheathed, foam dielectric cable, with a solid centre conductor. It is classified as an RG-8 type cable. The only disadvantage is that it cannot continuously flex around the rotator. If I had it to do again, I would probably try to buy the necessary number of runs of the stranded-centre equivalent, rather than make up the antenna coaxial stubs or jumper cables from the antenna to the feed line, just below the rotator. On the other hand, I think that this is fine for dipoles, etc. because the connection point can be secured and the flexing is not localized as it would be with a rotator. Shop carefully, the prices of cable by the reel vary and may be negotiable in bulk. The price is not always logical so do your homework. Electrosonic were kind enough to fax me their current catalogue pages on the appropriate cables and I used that to help find the right stuff. Be sure to connectorize the antenna end of the cables ahead of the time that you put up the tower and antennas.

The first thing to consider is the size of the hole. I did a little test and discovered that 10 pieces of RG-8/U can easily fit through a 2" hole.

Going through the concrete poured wall (alternative #1)

I am not talking about a concrete block wall (which is probably the easiest to go through). I mean a poured solid concrete wall. This is not a trivial exercise. To cut a 2.5" hole through 10" of old concrete which has a lot of stone in it will require drilling with a carbide or diamond core bit and a big heavy duty vibrating power drill. This is a big thing that looks like a small jack-hammer. It can take between 15 minutes and an hour of hard, noisy, work. The equipment can be rented for under $50. If you go this route, you must also decide if your cables will be below or above grade. Below grade is neater looking but has several additional issues including water proofing.

Going through the exposed framed wall (alternative #2)

This is not referring to an exterior brick wall. I mean a wall with some sort of siding and wood framing inside. My exterior wall is rather a complex structure. It has a 3/4" thick cedar siding, a layer of Tyvek wrap, a 3/4" thick plywood sheeting, and a layer of insulation. In my case 10" of glass wool type insulation was encountered. I chose to go through the outside framing joist and a another floor joist (I'm sure there is a name for this but it escapes me), because the alternative was to knock a hole through the wall from the inside and then bore down through the floor into the basement. By drilling through the floor joist, I ended up in the basement with no bends, etc. You have to measure very carefully to end up in the right spot. If possible drill a test hole. I was not able to drill a test hole, but was just lucky I guess. I used a 2.5" hole saw and was prepared to use a bit extension but didn't have to because I drilled from both the outside and then the inside. Using an extension bit would be very tricky because a large hole saw tends to bind quite easily with just its regular short bit. An extension bit might be a real challenge. Once I drilled throught the wall and the first joist, I pushed the conduit through the fibre glass, and was able to look up, when in the basement and see a bit of the conduit. I then was able to line up the inside hole with the pipe. Be careful, its difficult to repair mistakes.

Conduit

If you want to do a good quality job, seriously consider putting your cables through a pipe or conduit, similar to the grey PVC sometimes used for street power entrance to new homes. This will keep your cables neat and manageable, and allow you to better seal the connection into your house. A 2" i.d. translates to 2.5" outside diameter PVC. Your conduit should extend into the tower area. My conduit was above grade at about 18", and I put a 90 degree elbow in mine, pointing down. This will keep the water out and force you to bring the cables down and then up into the conduit. This automatically creates a drip loop on all your cables to keep water from running in. I had some old plastic eavestrough which was taken down last year and was lying behind the shed. I cleaned this up and used it as conduit inside the basement. It keeps everything much neater.

Just a footnote: I thought that 2.5" hole would give me lots of room for cables. For a modest installation, I' d now recommend 2 of these side by side - trust me, you will fill the first one quickly. Why 2 and not a 3" hole? Well you can consider a 3" hole but drilling a large hole like that through an outer framing member of your house may create some mechanical problems. I feel that two 2.5" holes present far less weakening of the framing.