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

[Steve - WB3HUZ]

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.

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. 

[KM8AM]

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

[KB2WIG]

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

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


klc

[k4kyv]

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.

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.

[K0ARA]

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

[KM8AM]

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......

[k4kyv]

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.

[Steve - WB3HUZ]

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.

[K5UJ]

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

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.

[KM1H]

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

[Steve - WB3HUZ]

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.

[k4kyv]

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.

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.

[Steve - WB3HUZ]

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?

[k4kyv]

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.

[KM8AM]

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?

[k4kyv]

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.

[K5UJ]

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.

[KM1H]

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

[WA2TTP Steve]

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.

[k4kyv]

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

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.

[KM1H]

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

[k4kyv]

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.

[K5WLF]

...Plus the FAA folks in Seattle are really working with us to keep the costs down....

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

[WA2TTP Steve]

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.

[KM8AM]

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?