Construction info for 1/4 wave 160 mtr vertical??

[KM8AM]

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

[K5UJ]

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  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

[KM8AM]

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

[k4kyv]

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.

[KM8AM]

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

[Steve - WB3HUZ]

New insulators and tapered base sections are ridiculously expensive.

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

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

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.

[KM1H]

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

[k4kyv]

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

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.

[K5UJ]

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

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    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

  

[Steve - WB3HUZ]

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.

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.

[k4kyv]

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, 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.

[WA2TTP Steve]

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

[K5UJ]

<<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.

[KM1H]

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

[N4LTA]

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.

[Gito]

Hi,

I used this ceramic insulators.

Gito

[Steve - WB3HUZ]

I doubt there is a lot of ground loss with 1/2 w. (180 degrees) verticals.

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.

[k4kyv]

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.

[k4kyv]

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.

[k4kyv]

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

[K5IIA]

that is awesome

[KM8AM]

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.

[K5UJ]

I doubt there is a lot of ground loss with 1/2 w. (180 degrees) verticals.

You may doubt it but measurements and modeling show it to be true, especially at HF where groundwave is irrelevant.

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.

[K5UJ]

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

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

[k4kyv]

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.