The AM Forum

We're looking for any and all helpful info on building a 160 vertical.

Searching this website and the internet hasn't yielded much so far.  Don's pics were great though.

We live 0.8 miles from a local airport and just received FAA permission for our 104 ft LUSO tower purchased at the Dayton Hamvention.  We do have to light the tower.

Now we're going to apply for a full-size 160 vertical.  That way we only have to light one tower.

We have the Rohn 25g and a 2" mast for a tuning stub.  We plan to use an inverted top section to insulate the base and Phillystran for guys.

Any advice, websites, books, or hints would be greatly appreciated.  We're also looking for a suitable base insulator.  We don't want to buy the Rohn base insulators.  We heard machined piece of Delrin may do the job, but an old broadcast insulator would be great.

Thanks in advance,

Ken, KM8AM and Karen, KM8Q
Urbana, OH

Well I had a reply for this and Safari crashed  ???  

take 2:  Hi Ken and Karen,

welcome to amfone.net.  disclaimer:  I have never owned a tower.  Be that as it may, I think it is inadvisable to use a top section to serve as a bottom with a stack of R25 on it for a 160 m. 1/4 w. vertical.  It is not designed to handle that much downward force--at least, I would not chance it.  You need to get the actual Rohn tapered bottom section, the one built for that service.   for one thing, such bottoms are usually built to be used to jack the tower up when the insulator has to be replaced.  You can't do that with a top section.  If you have to lamp the tower and you are going to directly excite it with RF, you are going to have to have a way to decouple the AC service from the tower--in broadcasting this is done with for example, an Austin ring transformer:
http://www.amgroundsystems.com/WMBG_026.jpg (http://www.amgroundsystems.com/WMBG_026.jpg)  but you might get by with some less expensive way of doing it.

In that regard, I'd probably try a skirt of wires standing off from the tower and insulated from it, and feeding them with RF.
 three wires 120 degrees apart and bonded with a ring at the bottom should be okay.  BTW, that also gets you around needing a base insulator. 

If you want a tapered bottom and a single point insulator then I do not recommend machined delrin--you are better off with a genuine ceramic base insulator designed for this purpose.   Some hams use leg insulators and they may be okay for shorter towers (1/4 w. 75 m.) but when you start getting up over 100 feet I would not trust them for the long haul, i.e. decades of use.

I hope you don't have to paint the tower as well.   Make sure the bottom insulator is up on a concrete pier elevated a few feet above ground.  If there is some height below which you don't need to use warning lights on the tower, say 60 feet, I'd put that up and go with an inverted L on 160.  Much less hassle and with a full ground system, almost as good.  Complying with FAA requirements can be very costly and a hassle to manage.  For example, you may have to have a tower monitoring system designed to activate an alarm when there is a lamp failure, then you have to immediately notify the FAA....in my opinion this is all stuff you want to avoid for ham radio.


73

Rob

Rob,

Thanks for the info.  This is just what we're looking for....how to avoid the potholes in the road to success.

We had a option to paint the tower and add a red light, or not paint and use a medium intensity, dual white and red LED system.  We chose the dual LED.

FB on the correct tapered section.  We'll start looking for ceramic insulators.

Interested if anyone out there is using the skirt system?  Would simplify the install, but interested in the performance trade-off.

Thanks

Ken

New insulators and tapered base sections are ridiculously expensive.  I paid less than $100 for my Rohn 25TG base section in 1980, while a regular 10' 25G section cost about $38.  Today, a regular 10' section goes for about $100 (last I heard) but someone told me that the tapered base section is selling for about $800. In 1980 they wanted $510 for a base insulator.  I hear that now they go for about $2K.  I picked up a spare insulator at a hamfest for $25, but I don't want to  get  rid of it, since I like having a back-up just in case something happens to mine.

You might be able to find a used one, maybe from a small AM station that has gone dark, or changed their directional pattern.

Speaking of stupidity, a station in a small town about 60 mi. from here went dark.  They had a 4-tower directional array using Rohn 25 towers.  The owner told the local ham club they could have the towers in exchange for taking them down and removing them from the property.  Some of the members who knew how to do tower work dismantled the towers, and club members divided up the sections...  Typical Hammy Hambone fashion, a couple of the tapered base sections ended up buried in concrete to serve as the bottom section of a run-of-the-mill Hammy Hambone tower.  They could have purchased a pier pin, or made one by cutting the bottom 12" or so off a galvanised 8' ground rod, set the pin in the concrete, and the tapered base section would have fit right over the pier pin.  Those  sections have a hole in the base plate just for that purpose. One of the base insulators reportedly got broken, but the others were eventually sold, along with some of the hardware.

I agree with Rob that an inverted top section would not be designed to handle the downward vertical force at the tower base.  The legs at the tapered part of the 25TG base section are reinforced with solid sheet steel welded to the sides of the rungs, and the base  plate, about 5/8" thick solid steel, is welded to the bottom of the rungs.

An alternative would be to have an adaptor plate fabricated at a machine shop. Get a scrap piece of 5/8" steel plate, have them cut it into a circle, and weld three cylinders (water pipe would do) of the proper diameter to fit right into the bottom of a regular 10' section.  Drill holes to accommodate nuts and bolts just the same as what is used to attach regular sections together, and use a regular section as the base section.  The taper is not necessary.  Many small broadcast towers don't have one. I wouldn't try to use a regular pier-pin base plate designed to sit flat on concrete, since the metal is too thin.

I had a machine shop to fabricate an adaptor plate somewhat similar to what is described above for mine, because the insulator was designed for a different  tower and the mounting holes didn't match up.  I gave it a  couple of coats of aluminium paint.  After 30 years, that paint has resisted rust better than the hot-dipped galvanising on the tower proper. I have re-coated it once.

If you can't find a real tower base insulator, I wouldn't be afraid to use a large ceramic insulator, maybe 6" to 8" tall and about 4" in diameter.  I have seen such insulators used as stand-offs in electric power sub-station equipment.  You would have to fabricate a fool-proof method of attaching a pier pin to the top of the insulator, and of course, the home-made base plate would need to have a hole at the mid-point to accommodate the pin. The stand-off insulators I have seen have 3 or 4 tapped holes in the steel casting at the top of the insulator.  A small plate made of 1/2" steel with holes drilled to match would be bolted to the top of the insulator, and a pier pin would be welded vertically to the plate at the mid-point.

The broadcast base insulators are usually hollow, to take advantage of the air dielectric and minimise capacitance across the insulator, but for a quarter-wave vertical, the base impedance is low enough that the extra capacitance from a solid dielectric ceramic insulator wouldn't hurt anything.

Stay away from such Hammy Hambone techniques that I have heard of, as stacking sheets of plexiglass, or using a piece of wood or a glass bottle for the insulator.

A friend of mine found a 15" long, 6" diameter power standoff insulator and buried half of it in the concrete and attached a pier pin to the top.  The only problem with that would be what to do in case that insulator got damaged and had to be replaced.

It sure seems we could make an appropriate base a lot cheaper than the Rohn tapered section.

There's a surplus place called Mendelson's in Dayton that has tons (literally) of commercial power stuff.  Karen and I will hit there tomorrow to look for insulators.  Also hope to find a big knife switch.

We've been watching the dog house project and plan to build a "northern canine campus" on the farm for the tuning network.

Ken

No need for the tower to be insulated. Tons of info on shunt-fed arrangements on the Web or lists like TopBand.



Phil, K2PG has a folded unipole system on 160 meters. There was a good article in QST some yeara ago on folded unipoles too.

I don't think there is much, if any tradeoff in performance, if done properly. The radial system will make or break your system.

I had a 90' 25G with a 10-15-20M Christmas tree on top and Phillystran guyed. It was shunt fed for 160 and after I figured out about grounds I was over 200DXCC in a few years and moved here in 89.

With 60 radials on the ground it was OK but not a pileup buster. Then I added 2x4" mesh welded and galvanized and plastic coated fencing on the ground, 2' x 50' and a lot of soldering interconnecting wires to the ground ring. It was an instant success and I was accused by a few of adding a 6-10dB amp :( but it was still the same 1200W amp.

There is nothing wrong with an inverted L either with most of it vertical. All verticals require similar attention to the grounding.

Here Im sloping a pair of wires from the top guys of the 180' tower and use elevated radials which work great on this rock pile hilltop. Im trying to get a 4 square up using long ropes off the tower for element supports but have had a lot of distractions this year.

Carl

Someone could manufacture an after-market tapered base / base-plate combination that fits directly onto the bottom of a regular tower section, built to Rohn tower specifications, a lot cheaper than what they sell them for.

Directly grounding and shunt feeding or using the folding unipole works ok, but lacks the flexibility of series feed.  For example, I plan to expand mine to work as a half-wave vertical on 75/80.  I have tried it a  couple of times with an outboard JS tuner and it worked, but the new tuner arrangement will include a permanent 80m vertical tuner.  I am eager to check out how it compares with the dipole in Europe.

The perpetual house painting project has slowed down the antenna project to a crawl. The farmer has harvested, but I haven't even redeployed the full size beverage yet.

The Lapp and Austin insulators that are hollow are filled with oil.  I don't know what type of oil and no longer remember the reason for that instead of making them solid.  

Don't stay too long in Mendelson's.  The air in that place is not what I'd want to breath all day.  I'm not kidding--the joint needs to be cleaned out.

Okay on the lamp for the tower.  I forgot that FAA allows some casual (for lack of a better term) warning lights as opposed to the full blown deal with the big red beacons and markers.  Those beacons are around 3 feet tall and 18" diameter.  It would be wild to have one on R25.   The beacon wind load would probably sway the tower  :D  Just kidding, sort of.  But we have a cell phone tower near a local airport here that has the white and red LED beacon with a strobe.  

You can probably decouple the AC with a small isolation transformer since the load is only the LED lamp but experiment first to see if you need it.  IOW, if you go the folded monopole or skirt feed or inverted L route (or anything else that does not require insulating the tower) the AC service to the lamp may not detune the driven antenna or if it does, changing the way it is routed, by for example, burying it, might solve that problem.  Then the the other factor is lots of RF on your AC service and how severe that problem is and whether or not you can live with it.   If any of these issues are untenable then you have to get an isolation transformer.  After that, you should investigate lightning protection measures for your power line to the tower lamp.   I guess whatever hams do for power line protection to rotators will work for a warning light.

If you can deal with all this FB but if FAA will allow an unlamped tower at say 1/8 w. high on 160 then I advise trying one of the shorter options others have given to see how well that works before getting into wiring for an obstruction warning light.

Rob

  

It may work better, but in general, 1/2 wave verts don't work as well as 1/4 waves ones. Unless you have radials that are several wavelengths (maybe many) long, the ground loss will be high on a 1/2 wavelength vertical.

If you want to strap into EU, hang a two-element wire array of the top of the 120 footer. You'll be in the 99th percentile of signals out of the USA.

Rob, the Lapp insulators, at least the older ones, were simply hollow, like a ceramic coffee cup, with no oil.  One of the maintenance essentials is to make sure the weep  hole at the bottom doesn't get blocked (usually from some critter building a nest just inside  the hole).  If that happens, it will fill with rain water and the insulator could crack in freezing weather.  The reason for the hollow insulator is to reduce capacitance and rf dielectric losses in the ceramic.  Pretty much the same  reason that an air-core rf coil is more efficient than one wound on a ceramic coil form.  I would assume that the oil used in the oil-filled ones has a better dielectric constant than the ceramic material used to make the insulator.  It looks kind of freaky when you see a 300' tower supported by a hollow ceramic insulator with walls less than 1" thick! The engineers knew what they were doing.

For the radials, DON'T use lead/tin solder to attach the wires to the ground bus at the base.  In about 30 days of contact with moist earth, the solder will turn to a white powder and the radials will literally fall away.  I once had a ground system soldered that way, and had to go out and re-solder the radials about once a month throughout the operating  season.

Instead, use a silver alloy brazing rod (http://www.georgiacopper.com/BrazingRod.html), available at any plumbing supply store.  It is now against plumbing code to use lead/tin solder to sweat copper pipes, so the silver solder is widely available.  It isn't dirt cheap, but the price  is not outrageous either.  It comes in "sticks" about 18" long, in the form of a flat rod, about 1/8" wide. You will need a Mapp Gas torch; propane torches don't get hot enough to melt the solder.  No flux is needed.  Once you get  the copper hot enough, to a dull red glow, it will melt the rod and suck the liquid solder like a sponge soaks up water.  No need to polish the copper.  Just use a wire brush to knock off any scaly stuff. The hot torch will burn away anything else.  After 30 years in the soil, the soldered connections between radials and the copper strap ground bus on mine are still intact. One note of caution: be careful when soldering the radial wires.  I used #12 bare copper wire, and found that it is easy to overheat the wire with the Mapp Gas torch and melt it to a blob at the end if you are not careful.  Just keep the copper no hotter than a barely perceptible dull red glow and you are OK.

I would NOT fool with one of those Hammy Hambone "radial plates" that use screws to attach the ground radial wires. Even commercial grade ground clamps affixed with a stainless steel screw will work itself loose from the ground rod after a few years. This is probably due to expansion and contraction of the metals with wide temperature variations over the seasons of the year.

I use a shunt fed 70’ Rohn 25 on 160 with pretty good results. I use shunt feed because this is my only tower and must serve all my tower needs. There are presently 10 antennas on it and all the feeds and control lines come off at ground level and go underground to the house. Using a base feed would make this multi use very complicated.

My configuration is the 70’ tower, 12’ of mast above the tower where 4 beams are mounted, a smaller mast above that holds a 2 meter Ringo Ranger vertical. The total height of this system is 95’. The resonance frequency is 1.90 Mhz with all the top loading of beams and 2 meter vertical extending the height. I use a modified Gamma match feeding the tower at the 20’ level. I have 25 radials plus the underground feed lines act a radials (I hope) because there all bonded to the tower base.

Good luck with your project.

Steve
WA2TTP

<<It may work better, but in general, 1/2 wave verts don't work as well as 1/4 waves ones. Unless you have radials that are several wavelengths (maybe many) long, the ground loss will be high on a 1/2 wavelength vertical.>>

I doubt there is a lot of ground loss with 1/2 w. (180 degrees) verticals.  Broadcasters use them often with 1/2 w. radials to lay down a lower angle and extend the groundwave field intensity, but if the ground loss were much higher they would not use them for the field intensity would be diminished and they would save a lot of money by sticking with 90 degree towers instead.  Actually broadcasters use 190 to 200 degrees to get just below the 5/8 w. length to eliminate the high angle lobe that you get with 5/8 w., but I think my point is still applicable. 

I think hams have poor results with 1/2 w. verticals on 80 m. because they don't do them right--they don't have enough 120 foot long radials on or in the ground for one thing, and the propagation conditions favoring the extreme low angle you get are not often there.  The angle for skywave you get with 1/4 wave is much higher, around 45 degrees and skywave with that angle is almost always available after dark.   

Don thanks for the radial etc. information.  I bet the insulator oil was a later fix to get around the hollow interior and weep hole clogging up/interior condensation problem.   Well, I use the s.s. radial plate here with s.s. hardware--nuts bolts lock and star washers with stripped no. 14 solid wrapped around them and when I went out a few weeks ago to add a copper strap to some of them I found them as tight as when I torqued them down 6 or 7 years ago with the copper still shiny but I have no doubt a copper strap ring with braised radials is much more reliable especially for burial.

At a prior QTH I had a pair of 80M 1/4 wave cage verticals hung from pine tree branches about 6' away from the trunk. They were also used as 1/2 wave on 40M with endfire and broadside selectable patterns. Lots of radials, about 60-70 of mostly 70'. Worked gangbusters on 80 but only fair on 40 except when a real low angle was really required. I soon installed a 120' tower with a KLM 4el 40 which generally owned the band around New England.

When I moved here that KLM went to 180' and I also found that it was often too high for Europe but it would run LP JA's forever and blow right thru the rest of the US in the mornings to the most elusive Pacific and Asian DX. It also silenced the Woodpecker many times. I then added another KLM at 60' with upper, lower and both selections and was amazed at how propagation angles varied.

YMMV for 80/160 but Id study N6BV's propagation angle analysis.

Carl

You can use "station insulators" made for power substations - 15 KV is probably the right size. They are common and have a bolt circle flange at each end. I have three that were given to me 15 years ago.

Hi,

I used this ceramic insulators.

Gito

You may doubt it but measurements and modeling show it to be true, especially at HF where groundwave is irrelevant. The pseudo-Brewster angle will be well above anything approaching groundwave for a vertical radiator atHF. For a 1/2 wl vertical, earth return current peaks at around 0.35 wl from the radiator. So you are correct, at least 1/2 wl radials are preferred. Even at that length, they do nothing for the Fresnel zone losses. Unless the earth conductivity is high (like sea water) most, if not all the gain from a 1/2 wl or longer vertical is eaten up.

Here are some snapshots of the base section of my vertical and how I mounted the insulator.

Fig. 1 shows the tapered base section, base insulator and concrete  base pier.

Fig. 2 is a close-up. Notice the logo on the base insulator is printed upside down.

Fig. 3 detail showing the logo with the photo inverted.

Fig. 4.  Close up of base insulator and base plate.  Those are un-galvanised cast iron, coated with aluminium paint, installed nearly 30 years ago, and the paint was touched up once, maybe 15 or 20 years ago.

The base plate has a little pier pin that sticks up vertically, maybe 3/4" in diameter, and 1 1/2 inches tall.  The bottom casting on the base insulator has a matching hole, and sits on the base plate, held in place by the pier pin.

Fig. 5. Adaptor plate. Notice that the tower base section has a steel plate welded to the bottom of the tower rungs.  The adaptor plate is below the plate on the base section, and slightly larger in diameter. The top casting on the base insulator is bolted to the adaptor plate from below, and the base plate on the tower section is bolted from above. As you can see, the holes the base plate and the holes in the base insulator do not line up.  I had the adaptor plate cut from a piece of scrap steel, with 6 holes drilled, 3 for the tower base and 3 for the insulator.  Each hole was tapped with threads to accommodate the bolt.

Fig. 6.  Another close-up from a different angle shows how the tower base is bolted on to the adaptor plate.

Figures 7 & 8 show the adaptor plate attached to the tower base from differing angles.

that is awesome

Thanks for all the inputs.

Don:  The pics are great and give us what we need to fabricate an adapter plate.
We can see the new doghouse - looks fb.

Will start the radial field soon. Although it may be better to wait for the grass to be growing.

We toured the Hughey-Phillips Obstruction Lighting (formerly Honeywell) factory in Urbana last week.  We found some smaller, more efficient, FAA-approved LED lights.  It was interesting to see the BIG 2400 W all-glass beacons.  What monsters!

We're taking some of the new LED flashing lights into the lab to run 1.8MHz to 1.2GHz EMI testing since the company only ran FAA cert testing from 25 MHz and up.

Depending on the results, we may paint the tower (to avoid the req for daytime white flashers) and then we can use just a steady Red at night.

Although I envy folks that can put up any tower any time, we just love the view from our ridge-top log house and farm.  Plus the FAA folks in Seattle are really working with us to keep the costs down.

Yeah, but no one cares about HF.  This discussion is about ground mounted base insulated and fed guyed towers on 160 m.

I apologize--I just went back and saw my earlier comment pertained to 1/2 w. verticals on 80 m.  My mistake.  And I appreciate the modeling information, thanks Steve. 

There's a VE3 who has an insulated tower on 160 using the same type insulator as the one Gito has.  I saw a photo of the base in QST and it looked pretty good.  Then I looked the guy up on-line and saw more photos.  He's got the tower loaded with yagis--not sure what that does for his monopole performance on 160.  But worse, there was one photo showing his ground system around the concrete pier.   Instead of a nice copper strap radial ring and no. 14 or 12 solid copper wire he's got what looks like steel electric fence wire bunched up in a couple of spots and clamped together with lugs.  It's always amazing when someone gets one thing right and does a half-assed job on something else like the ground system.

Putting in the ground system should be about the last thing you do.  First you have to site everything, figure out where the base and guy anchor points are going to go and excavate and set them up and have the concrete curing.  You need to have the base pier and guy anchors in and everything ready to stack steel.  The reason to hold off on the radials is that you may have some heavy construction equipment out there--concrete truck, maybe a crane and they'll tear up your radials if you don't have them plowed in well below grade.    You also have to figure out how you are going to route your feedline and place the doghouse--if you use a ditchwitch to trench a cut in the ground for the feed, you have to have that done before the radials so they can go down over the feed.  Basically the ground system is about the last thing you put in.  P.s. if you really want to do it right as in a broadcast grade tower, you should tack weld each section together but for ham radio that is probably overkill.   

Rob

I recall reading in some broadcast engineering text before I put mine up that with galvanised towers where the rungs telescope into each other as with the Rohn 25 and 45, that welding or brazing  the sections is not necessary.  OTOH, solid steel towers where the sections are held together with bolted flanges may need extra bonding, particularly if they are not galvanised.  Running a heavy gauge wire down each tower leg should work just as well.  Galvanised steel would probably be better than copper to avoid any problems with dissimilar metals.  You would never want to run bare copper where it would come in direct contact with galvanised or zinc plated steel. Perhaps an even better alternative would be to outrig a 6-wire cage surrounding the tower. It could be insulated from the tower so that copper or copperweld wire could be used.  That would give the additional advantage of fattening the tower and thus increasing the bandwidth of the vertical.  Some broadcasts stations have done that with skinny towers for improved bandwidth when they decided to try IBOC digital.

I agree with what Rob said about waiting and putting down the radial system as the very last step.  I didn't get my radials installed until over a year after the  tower was up.  In the meantime I used the 80m dipole for 160. I didn't even try to run a JS vertical with a makeshift ground or no ground system at all.

If I can find it, I'll photograph and post a snapshot of the homemade radial plough that I used to bury my radials using a Troy-Built garden tiller as a tractor, with the tines removed.

Ultimately, I was not saying don't use a 1/2 WL vertical on 80 meters. Rather, if you already have a 1/2 WL tall tower on 80 meters, you'd get a better signal into Europe using the tower to support a 2 element horizontal array (at least from the eastern USA). You'll hear better with the array too.

Will absolutely wait on the radial field!  I guess I was wanting to "see" progress while waiting for the FAA.

Then surprise surprise: The FAA approved us using one L-810 steady red on the LUSO tower.  This gives us time to check out an inverted L and maybe a shunt fed setup while the 160 tower is in work and yes we have to apply again for that one.

With the simple/cheap light solution on the LUSO, we can now move the 160 tower away from the others.  The FAA wanted the 160 within 150 ft from the others if we wanted to claim "shielding" and therefore the need to only light one tower.  Now we can put L-810s on the LUSO and the 160.

Again, thanks for all the great comments.

Ken

I loove the soft on/off of the tower beacons.....

The snap/snap/snap of the white strobe is displeasing to my sensibilities.


klc

I tried the 160m vertical on 75 a couple of years ago with a JS tuner set-up.  Worked up and down the east coast and into the mid west.  Signals, both transmit and receive, were pretty much typical of what I get with the 1/2λ high, 1/2λ long dipole. Couldn't really tell any difference, but wasn't set up for A-B comparisons. On receive, noise would likely be a chronic problem with the vertical.  The beverage just about always does better than the dipole, both with signal to atmospheric noise ratio and  signal to electrical noise ratio.

I hope to experiment with the half-wave vertical some more this winter, particularly if I hear any of the AM guys from Europe.  But I built the vertical for 160, so won't be disappointed if it turns out to be a dud for 80m DX.

I  could extend the 80m dipole to two halfwaves in phase, but don't know how that would affect the 160m vertical, and would gain only a couple of dBs over the dipole anyway.

Ken, you could locate the vertical about 130 ft. from the other tower to satisfy the FAA, and put a radial system round both.  Maybe shunt feed the other one if adding a second base insulator is too formidable a project.  Then try phased verticals both on 160 and 80, if your geography allows the proper placement of the towers for directions you want to reach.

I have worked some guy on 160m AM out west a couple of times, in west Texas or maybe even farther out, who had a switchable multi-tower vertical array. Six full size quarter-wave towers IIRC.  He started out with a good signal.  Then he told me he was going to "swing the beam in my direction" and he gained another 10-15 dB.  I was amazed at the difference.  It all made more sense after he told me what he was using; I had pictured a full size 160m rotatable yagi on top of a 200' tower.  I can't remember his callsign, and I think he has since moved.

 Marv KC9VF has a nice vertical setup. Always a Big Signal into KC.  http://harvesting.com/tower/index.htm   

it sure is nice to have a wife (KM8Q) that's into radio!

When I told her that the FAA gave us the go and that Don suggested phased verticals, she said "go for it"

What more could I ask for......

If you were to go the phased vertical route, be sure to properly overlap the radial fields of the two towers.  You don't just lay one set of radials over the other.  Rather, draw a straight line that is a locus of all points equidistant from the two tower bases, from one point where the two circles intersect, to the other on the opposite side.  Lay a buss wire along that line.  In the area where the radial fields would have overlapped, terminate each radial to the buss wire, even though it is not a full quarter wave long.  Of course, use silver alloy brazing rods and a Mapp Gas torch to bond the wires.

You don't need a second tower for an array - a 3 element array!

Run sloping ropes off the single tower to support up to 4 wire top loaded Ts. The Ts are all cut to be a little short at the center frequency of the system and have loading coils at the base. The tower is the driven element and two of the four Ts (let's call them T#1 and T#2) work as a reflector and director. The reflector is created by the coil at the base of T#1. The coil is shorted out on T#2, and since the wire is cut short, it acts as the director. To switch directions, short the coil on T#1 and un-short the coil on T#2. The other T's (T#3 and T#4) are left floating (not connected to ground) and are essentially RF transparent. To beam in the remaining two directions, T#3 and T#4 are connected as described above and T#1 and T#2 are left floating. Finally, you can float all four of the Ts and just use the tower for an omnidirectional pattern.

This set up, with a good radial system is good for 5 dB gain over a single vertical and 25-30 dB front-to-back ratio.

That guy's got a nice looking tower from what I can see in the photos.   Never heard his signal--we must have different operating habits and don't cross paths.  The one thing I could see that I'd change is I'd loose the higher inductance ground cables going from the base down around the concrete to the radial ring and put in four wide copper straps.

I wonder how that would work with a shorty vertical dipole Steve?  I can easily do the 4 or more sloping wires from the top of the 180' tower as Ive been working on getting the 4 shorty telephone poles planted.

Is your idea any better than a traditional 4 square?  It would require 4 high currrent relays, probably vacuum, but not the phasing headaches to get peak performance.

Carl

It has a little less gain than a 4-square but much better F/B and overall backside pattern.

No phasing networks or hybrid boxes are needed, so it's both simpler and less expensive.

It's not my idea. K3LR and others use this system on 160 meters.

Wouldn't you need a separate radial system for each one of the T's?  And I'd say you could  get better bandwidth by using a 4-6 wire cage for each vertical element instead of a single wire.

Yes, you'll need a radial system under each wire. That would be true of any multi-element vertical array.

No reason why you couldn't make the wire elements a cage. I may model this to see how much difference it makes. What sort of BW do you see on your tower?

Tuned to 50Ω with L-network at the base of the tower, 1:1 swr at 1900, swr measures somewhere between  2.5:1 and 3:1 at 1800 and 2000.

The actual base impedance measures between roughly 150Ω and 350Ω across the band with G-R antenna impedance bridge, with similar figures for the +j factor. I have the exact data out in the shack.  The dipole obviously is adding a lot of top loading so that the vertical acts more like a T than a pure quarter-wave Marconi. The close vicinity of the feedline to the tower, as the feeders are strung up through the interior of the tower, makes for a lot of coupling between the dipole and the tower.

One thing I'm still studying is the guy material.

EHS, fiberglass rods, Phillystran....Each has its pros and cons.

EHS has a long history and is definitely strong and has minimal elongation.  But it needs to be broken by insulators.  Multibanding the tower seems to make breaking the guys a challenge.

Phillystran may not need insulators, but it has more elongation, needs EHS near the ground, and has been around only since the 70s.

Fiberglass is just hitting my radar screen.

Comments?

According to the NAB broadcast engineering handbook, the guy wires should be broken up at a minimum of 1/7 wavelength at the highest transmit frequency.  I wanted mine to be rf transparent all the way through 40m, so I broke them up every 18 feet.  That was probably overkill, and required over 100 insulators, but I already had the insulators on hand and the hardware was a lot cheaper (in real money) than to-day.  If you are only interested in 160, it would be OK to break them up every 72 ft.  If you want to include 75m, then every 36 ft.

If you use metal guy wire and insulators, I would recommend terminating the guy wire sections to the insulators with "guy grips" or "pre-forms" instead of the little U-bolt clamps.  The guy grips are more expensive, but the clamps are a lot more work and time consuming, and probably not as secure.  You would need 6 clamps per insulator.  Lately, the clamps I have seen for sale for 3/16" guy wire are only zinc plated, not real hot-dipped galvanised. Those things would be rusty within a year at most locations.

I use three insulators in series where the guy wire attaches to the tower.  Some broadcast stations use fibreglass rods, but I have seen the ones the power company uses on utility pole guy wires split and break, and I don't know if the ones sold  for tower use would be any better.  BTW, use guy grips specifically designed for tower work. I was informed that the ones the power company uses on utility poles are a different product, not rated to safely use with towers.

I'd never go through the business of using guy clips if I could possibly avoid it.  Think about if you have say, three levels of guys in three directions, that's 9 of them.  Now if you have each one broken up 5 to 8 times depending on length and on each insulator you have 3 clips (you may need more) on each side of each egg insulator, ....well, do the math and you have a hell of a lot of bolts to get tight.

And, all it takes is one of those cables slipping through or a few insulators cracking and crumbling and you got problems.  Of course if you do it right like Don has, plus many many broadcast stations it should be fine for decades.  But these days, I'd definitely look into some kind of composite non-conducting guy cable--you mentioned Phillystran (sp?); another one is Kevlar but I don't know if it is useable for guying towers.  What I have heard about it is it does not stretch out.

I wonder how often if ever, those insulated guys have to be taken down and have the clips retightened. 

One thing I forgot to mention earlier is that on your pier, if you are where the ground is spongy, you have to factor in earth compression and make the pier spread out more than average below grade and below the frost line, so the weight is over a wider area to keep it from shifting or sinking on one side.

The part you see in most tower photos is like the tip of the ice berg hi hi, but since you are not putting up a 800 foot blaw knox diamond you don't have to go crazy.

I used the chart out of the ARRL Antenna Manual and broke them up every 57' and have operated 160-6M mounted on or hanging off the tower including using the 80/160 inverted vee on all 3 WARC bands. No problems ever noticed. I define a problem as not being able to easily crack a pileup or not being able to work anything I can hear.

For 160 a pair of wires sloped off the top guys about 20-30' out and terminated in raised radials and a simple coax relay switched steering arrangement. Cardiod NE and SW and figure 8 broadside, worked gangbusters, had 15-20dB apparent F/B in cardiod.

Rob, I havent used guy clamps in decades, everything is done with guy grips, quick to install and reliable. I used Phillystran on a 90' tower at an old QTH and still had to use steel the last 20' to thwart any vandalism. Plus they certainly didnt have a solid feel up on a loaded tower. Im using 1/4" EHS cable on everything now.

Carl

Speaking of guy grips and EHS guy wire. I've noticed on my tower installation that I'm getting some rust on the grips and guy wire but only within about 6' of the top of the tower. Below that there is no sign of rust. The tower is 70' high. It's been up 25 years. Seems odd to me.

According to Rohn, if they are tightened properly the first time, they never have to be messed with again.  Proper tightening means a slight dimple in the dead end that is clamped by the "U" part of the clamp.  The U part should always go on the dead end; the other part should always go on live end.  The  theory is that the U bolt clamping tightly enough to form a dimple in the cable weakens it. Rohn says that surface rust on the clamps actually locks the nuts in place.

An incorrect way many towers are done is to use 3 clamps at each termination and alternate the direction.

I have 4 towers up here from 60-180' that have only been up 20 years and with fresh 1/4" EHS. The 3 upper guy levels on the 180' are all rusting with the upper ones the worse. The both at 100' have only the top 2 sets rusting and the 60' is starting to rust on the top set. The big grips are fine so far but well weathered.

I suspect it is industrial pollution from the coal plants in the Midwest and the way the winds hit this hill low and curve up with more force. Even the tower bracing on the 180' 45G is rusting above 100' and it was all new in 1990. Ive a lot of work to do next spring and summer it seems.

Carl

My tower has been up about 29 years now, and some of the 10 ft. sections are uniformly well rusted, while others hardly show any  rust at all. That tells me the hot dipping process they used was not uniform.  I have noticed that some of the guy sections are completely brown with rust while others are still well preserved.  And all my guy wires  came from the same spool of cable.

I'm not sure what tower professionals would say regarding when it is advisable to re-guy, but just guessing, I would say when individual strands in the cable are observed to show deep pitting.  Of course, that requires climbing the tower to inspect the upper guy levels, and even then you can only see the upper and lower ends of the cable, and you have to make an educated guess about the condition of the middle sections.

It seems that the FAA is becoming easier to work with and more 'human' these days. I had occasion to work with them about five years ago when we put up a 180' stick of Rohn 45G for the microwave link from our observatory back to campus. We're within the operational area of the Stephenville(TX)/Clark Field Airport (SEP) and our signal path crosses the Runway 14 final approach. However, it's well above the altitude that a landing aircraft would be.

The Fort Worth FAA office was wonderfully easy to talk to and work with. Truly a great example of what it should be like to deal with a government agency. I wish all government agencies were as good as the FW FAA.

ldb
K5WLF

I guess I'm not alone. I think I'll make a spring project out it. It's not to big deal to change the upper sections.

Went to Mendelsons and found quite a few ceramic insulators ranging for 3-5" in diameter and 4-8" tall.

The wider ones were short with steel plates on each end.  Seems stacking these would increase the capacitance.

Also, has anyone had to jack up the tower to replace the insulator?  It looks like the Rohn tower base section has holes that could allow a sturdy pipe to support jacking.

Is it overthinking the issue to incorporate lifting ears if designing a custom base plate for a regular R-25 section?

Tom, K1JJ recently mentioned jacking up a tower to add a base plate and pier pin.  Maybe he could describe how he did it.

Some larger towers with tapered base section have jacking ears. I don't know if the bolt holes in the bottom of the sections would support the weight of the entire tower without bending or tearing the metal.  Perhaps some kind of bracket system that would clamp onto the rungs of the tower with multiple  clamps on each leg might work.

In any case, one would need to be careful.  Hazardous job, both to the operator and the tower.  

Using a pipe through the tower to jack is a bad idea.  You need flat surfaces.  You don't want to find out you picked the wrong pipe the hard way, or have it roll off a jack.  The base has to be made to be jacked.  Consider small I beams, size depends on the tower.  Here's a link to a photo of some jack ears to give you an idea.  

http://www.fybush.com/Tower%20Site/030424/high-is-twrbase.jpg

This is the base of the WFAN/WCBS tower on High Is. in NYC--the two stations share the tower.  

Having written all that, consider that if you get a good base insulator, it will probably last longer than you.  A lot of stations on towers that date back to the 1930s are still on their original insulators.  

Some likely causes of base insulator failure: vandalism, accidental rifle bullet from a hunter, projectiles flung from a mowing machine, filling with water (blocked weep hole) followed by freezing.

WSM in Nashville and some other major stations built brick walls surrounding their base insulators to prevent them from being used for target practice.  WSM did theirs during WW2 when the station was used to transmit some kind of strategic data simulataneously with their broadcasts and they were concerned about enemy sabotage.

I have a spare base insulator, but have no idea how I would jack the tower to replace the original. I would probably construct some kind of elaborate jig for the purpose.  You would only need to jack the tower a few inches to clear the insulator and pier pin, but the scary part would be working near the elevated tower base while no insulator was in place.  I would probably cast some kind of reinforced concrete pillar to temporarily slip under the tower base just as the old insulator was removed, and slip it out as the new insulator was placed in position.  Something probably better left to a professional or at least supervised by one.

You wouldn't use just one jack, but three jacks supporting the base in a triangle, and in turn ease each jack up a little at a time.

I have heard of towers up to 150' or so being constructed on the ground and lifted into vertical position using a crane.  I suppose that wouldn't be a whole lot different from jacking up one from the bottom. I'm not sure how they would safely attach the cables from the crane to the tower, other than "very carefully".

There is a 500' tower on the next hill over from me that was originally built for CH 50 and a FM station. As the tower grew more users the base sections started cracking.

I watched a crew raise the tower and replace two 20' sections, they said they do it all the time and made it look easy.

Carl

I can't imagine a tower that wouldn't have enough safety margin to withstand the extra load from antennas on top, if everything was constructed according to specifications .  I'd bet they far exceeded the recommended wind load. Did they add a bunch of solid parabolic dishes?  The base sections didn't fail due to the dead weight of the antennas or dishes,  but from the resultant downward vertical force transferred via the guy wires from the horizontal forces of the wind.

You gotta also consider the feedlines.  Get enough dishes, cell phone, broadcast, two way radio etc. up there and the feedline weight really adds up especially if it's a tall tower like the 500 footer Carl mentioned--pretty long runs and some of the feeds are big and heavy if waveguide or big heliax.   Further get a lot of feedlines and it affects the windload.  Up north you also got ice shields adding weight.  I have seen towers with so many feeds the tower looks like a black stack in the air.  Now, if they have to be painted, you gotta have the feeds in matching orange/white colored sleeves so they don't affect the tower visibility.

There were no dishes, just another FM stick and several 20' 2 way sticks. If I remember the details the tower was Rohn 85 and already marginal at 500' with the original antennas on that hill. The site owner had been told that.

It doesnt take many 1 5/8" cables to add up the weight to more than the tower itself. Ive got a bunch of it out back and its a 2 man job just to roll 300-600' of the stuff.