The AM Forum

I am looking around at the various wires available for building the new antenna system here @N6YW.
Because I have this  Elm Tree in the yard, I am going to have to use insulated wire in case the wires come into contact with the limbs...or will I? I had a loop up here once, built from #10 AWG THHN. It arced frequently right through the insulation onto a limb. However, that was likely due to it being a loop. The new antenna should clear the upper canopy because of the 40' Military fiberglass poles being used this time.
What do you like and how well has it worked? The wires on the Wireman site look reasonable and because I live next to the ocean, and run high power all of the time, my choices are narrowed somewhat.
Billy N6YW

I think living near the ocean would call for using insulated wire. But then copper clad would turn a nice old buzzard green faster out there. All of my antennas are just plain copper wire. No steel no nothing. My 160 meter an is just # 10 insulated. I pre-stretched it with my pick up truck. If you try to remove the insulation it's very hard as the insulation has somehow been pulled into the wire. It's been up there for eight years now atop two pines at about 80 feet and rising. If you don't have any stress on the wire, plain copper should work fine.

The Flexweave 12 AWG stuff looks like the ticket for me, because it is easy to deal with and doesn't have a mind of it's own. I will be using a slingshot to shoot the pull line over the top of the tree.
When the wire gets pulled up, I can't afford to have tangle issues. This tree is such a PIA.
Hopefully by the time the antenna has been up for a couple of years we might have already sold the house and moved to the country. I really need 5 acres  8)

I use #8 Copper clad steel just because I have a large roll of it. Main antenna is # 10 copper clad steel (ex-railway telegraph line) because I had plenty of that when I put up the antenna. The stuff is stiff and hard to work with, but once up, it is indestructible. I would recommend it for tree antenna installation because the tree limb will probably break before the wire does, if you have good insulators that won't fail.

I also use it for open wire line, but my OWL is kept under tension with turnbuckles. I wouldn't recommend it for that purpose unless you can keep it under tension, since it wants to spring back into a coil if left to dangle on its own.

#8 solid copper or #10 for smaller antennas. Flex weave will rot sooner.
Every copperweld I ever used was junk. A flash of copper lasted one season before I could see rust.  My beach primary is solid copper. There is a Western Union splice that is older than I am feeding the pole pig that powers the house.

In that case, I should be buzzardly and put up the big stuff. It will match my neighbor's roof, green copper.

#12 or #14 THHN.

Billy,

With copper wire, in general, the finer the strand, the faster it will rot.   A fine stranded Flexweave will rot much sooner than say, a stranded #10 composed of (12) #24 strands.

A solid piece of #8 copper will last forever.  It's all about how hard it is to break down the diameter used. For example, a small .008" of corrosion depth on each fine strand of Flexweave makes a huge difference when all the strands are counted. However,  .008" of corrosion on a 3/16" diameter solid wire has virtually no effect.

TimTron has up a dipole made of solid #8? copper wire.  I remember seeing it at his RockPort location (near salt water) in the early 70's. It was blue. He still uses it today and is strong.

Here I use #10 THHN stranded with the PVC covering. Some of this stuff has been up for 20 years and is still bright inside.  I have my dipoles supported at the centers, so no problem with stretching.

As Frank said, be careful of the plating depth on copperweld. I, too, have used the cheap stuff and had it rust through within a few years. Once it breaks down the thin copper coating, the steel will rust and break quickly.  I would axe the manufacturer about the copper coating depth and compare this to commercial standards to better evaluate.

BTW, the big elm tree - how about taking advantage of it? Climb as high as you can and slide a pole up the tree trunk farther and lash it off. Use a pulley and then center support the inverted vee, etc. (Or maybe you are already doing this)

Yes, your antena wire may arc to the tree, depending on the voltage/impedance point. With a 1/2 wave dipole, the ends are the hottest. For multiple bands/openwire, there may be hots spots anywhere on the dipole depending on the freq being used. Keep it clear of the limbs since you are running QRO.

T

Thanks T.
I get that. I am thinking if the ends of the Flexweave were sealed in epoxy, how is the wire going to rot so quickly? I guess if the jacket is porous enough or breaks down quickly in the elements that would be the case, but even a polyethylene jacket can last at least 7 years in the sun and rain, salt air.
The chemicals in certain sheathing materials react in an adverse manner when subjected to different environments. I know this to be true from experience, especially in older types of sheathing from the 50's. Some of that stuff gets rather nasty.
Anyway, The pole idea is a good one and I have thought about that many times. This is an area where my Ham Licensed Wife might disagree though. Everything is a balancing act right?
If I finish painting the house, then she might agree hahahahahahaha!
Thanks guys!

OK Billy -

Yep, a pole slid up a  tree is really an effective way to get a high antenna without a tower.  Back in the 70's I slid some telescoping mast up a 50' tree and had an inverted vee at 70' at the apex fed with OWL. The mast sat on a limb at 40' and went up another 30'+ higher, towering over the tree. It may have been more like 80' high now that I think of it.  The dipole ends were pulled way out high into both neighbor's yard trees. Man, did that work well on 75M AM back in its day when a dipole at 30'-40' was the norm. TimTron stopped by and said it was the highest AMer antenna he had seen so far... ;D

OK on the Flexweave. I was talking about the bare Flex, not the jacketed stuff. I'll bet the Flexweave will be FB with the jacket and will last a long time, just like the jacketed THHN.

BTW, on the high mast - use the pulley rope as one back-stay. The dipole legs will help too. Tie a knot in the rope to act as a stop when the inv vee is at the top. Add two ropes to make it a tri-guyed mast.  With some work you can usually pull out the guy ropes and pull up the inv vee clear of the limbs. You may find that sawing a strategic limb will open up a clear area for the antenna work.

Good luck wid it, OM.

T

When I had the cloud burner up, I wove 14ga stranded THHHN through all kinds of limbs with a wrist rocket. I never had any issues. As a matter of fact, I'm using a section of that same aerial for my dipole, (the lay of the land/trees don't lend too well for a loop).

what you use depends on how much money you want to spend, the physical conditions, what's available and your location.    In a town, or any place where you can't completely control the area all around your antenna, I'd go with insulated wire.  If bare and it breaks for some reason and comes down on someone or somehow starts a fire while you are on the air you don't need that.  Also it makes some sense if you have a lot of antennas near each other like I do.  I had a bare wire dipole once and didn't realize it was swinging into a TV antenna I had up.  No damage fortunately and insulated wire isn't a fix for that, just extra protection.  Admittedly this all may be far fetched in your case so the insulation may be more for piece of mind.  If I were out in the country and I had complete control of the space all around my antennas for hundreds of feet, I'd get rid of any trees in the way, put up one or more towers, and have all bare wire because insulation adds weight.  

The span of the antenna and the wx it usually has to contend with are factors.  You don't have to worry about wind and ice and you probably don't have room for a long span.  this means you can probably get away with a wire that might otherwise stretch or break.  But, this does not necessarily mean you should go with something light weight.  I use no. 12 stranded house wire I got at Home Depot (mine has green insulation--I had some idea it might look better  ::) ) but my longest span is around 45 feet.   You may have to find a balance between gauge, weight and tension.   You have to sort of experiment.   Every support should have a marine pulley on it with the antenna rope going through the pulleys so you can hoist them up and down and alter the tension.  Too heavy gauge, weight and tension may mean your supports will pull over, especially in a wind storm.   Your end supports and any support that holds a bend have to be strong.  If you give the wire slack to relieve the supports, you may have too much sag and swing in the wind.   Think of the worst wx you have ever had at your QTH and put up your antenna with that in mind.  A common noob mistake is putting up an antenna on a nice calm summer day and it's on the ground with the first bad wx.  

@K5UJ
My first antennas were erected in Lake Tahoe 20 years ago. I learned that lesson the easy and hard way. It was easy in that I had 70' pine trees to support any antenna that I could dream of but the hard part was that 90 mph Winter storms that would rip down the Echo Summit bringing Gale force conditions and blowing snow which always resulted in iced over and ultimately, broken antennas.
My TH6DXX tribander lost it's truss cable during a storm and the icing broke the boom in half!
Anyway, all of your contributions are greatly appreciated. The rigging part is easy and I think I am going to take a closer look at the middle pole that was suggested. That would put my feed point up near the 60' ft. level which would rock big time. I think that would be enough to prevent the proximity of the Faraday Cage homes next to me causing so much grief. Now that my neighbors are on Dish Network, I no longer have to contend with TVI issues.
I will try the 12 AWG stranded wire first and see how it plays. My poles are fiberglass, so no problems there. I think the 60' ft. folded dipole with OWL is what I am going to try first.
It looks compact and lightweight enough for the site here. I am going to be creative out of
necessity. I'll share my findings with you all, and of course photos. Of course I ask the girls in my
Avatar to pose with the antenna before it goes up  ;D

You must have used copper clad electric fence wire. That stuff isn't worth bringing home. A microscopically thin layer of copper deposited on the surface of a steel wire. Kind of like "zinc plated" vs. hot-dip galvanised hardware.

Real copperweld is clad with copper that makes up 20-30% of the total diameter of the wire.  I used #10 copperweld for ground radials for a 160m inverted-L back in the 70s. Occasionally I still dig up a piece and the copper cladding is intact except for greenish corrosion crud on the surface.  I have filed and scraped it to see how much of the copper was still there, and most of it was.

The worst coperweld I ever had was some that I  bought from Radio Shack in the early 70s. I used it to make the end-fed Zepp I used when I operated from Cambridge.  The stuff kept stretching like pure soft-drawn copper, and the extra length would eventually be enough affect the settings for resonance with the antenna tuner.

The old maritime/marine radio intallations often used hard drawn BRONZE wire .

A popular wire for the old time multi-wire flat-tops and cage antennas in the 1920s was stranded phosphor bronze (http://en.wikipedia.org/wiki/Phosphor_bronze). The remnants of the wire antennas at the Marconi station on Cape Cod (now a museum) are made of solid wire that appears to be copper, though it could be phosphor bronze.

Phosphor bronze wire is still manufactured, but it isn't cheap.

I never had much luck using stranded copper wire for antennas.  It tends to eventually break wherever it flexes at terminations, from the wire swinging in the wind.  Solid wire is more durable. Soft-drawn copper tends to stretch and increase in length, although it can be converted to hard-drawn by pre-stretching the wire before building the antenna.

Interesting. I've found solid wire more prone to break from flexing when the junction was mechanically too tight, unable to move around. A good example is when openwire gets soldered directly to a stress point.   The problem is probably the way the splices/terminations are done...

Splices should always be floating with no strain. Do this by looping all wires thru the insulators and securing. Then the free floating wire ends get joined/soldered.  This way there is never any pull or flexing on a soldered joint.  Using a wide, loose, big loop to secure the wire to the insulator eliminates the leverage that will break a wire that is tightly secured to an insulator.

As for stranded wire, if it is supported at the center with no feedline weight, stretching should be minimal. It is designed to handle flex better. I've had #10 stranded THHN up for many years for the 260' parasitic loop quads. This is strong stuff. The tuning is critical for the DX window and I would see any departure in terms of changed f-b or swr.  I tuned them with beacons so they are critical. These parameters have stayed firm over the years despite ice storms and winds.  Again, it's all in the way they are supported. My quads are pulled out to form a square with maybe 20 pounds of pull on each side.   Of course, a dipole stretched out from each end with no center support is a different story and may need solid wire or copperweld. Still, I have 75M dipoles that use stranded #10 THHN supported with 60' spans that have survived ice and winds FB.

T

I agree with Don about Copperweld which is a trade name, the junk is simply copper flashed as with welding wire or single pass plated at about .010".

Rural telephone wire is still available in #10 and 12 with .030" plating and a black nearly impervious jacket. If its going to be swinging in the wind terminate with a couple of guywire clamps and bent around a thimble. Use regular stranded wire as jumpers to the coax connector or solder lugs.

Flexweave is considered unreliable junk by the many DXers and contesters who jumped on it early.

Its pretty hard to beat 7 strand hard drawn copper in most enviroments, I have some here thats been recycled for about 45 years from 5 QTH's.

Carl

My favorite antenna wire is the free kind..   Gov't surplus from the dump...

The TimTron showed me the way to strip insulated copper clad wire.

The thing to do is to heat the insulation before you strip it. If you don't, you'll end up removing some of the copper weld and expose the steel. In a few years, the antenna will break.

My #10 is old railway telegraph line.  Most of the rural open wire telephone lines used steel wire, in many cases almost all rust by the time they replaced those lines with enclosed cable. The rail companies used copperweld because it resisted corrosion from the sulphur-laden smoke spewed out by the old steam locomotives. Steel, even zinc-plated, wouldn't have lasted more than a couple of years in that environment, but the copper jacket was highly resistant. When I got mine, it had a nice hard green patina but most of the copper was still there.  Even the stuff I buried for an earlier radial system decades ago still has the copper jacket almost intact when I happen to dig up a piece that's still in the ground.

I probably didn't terminate the stranded copper correctly, and soldering it was most likely a mistake.  Split copper bolts work well for connecting  two  copper wires together.  Never use galvanised clamps for the purpose, because copper and zinc are highly reactive to one another and will corrode the first time it rains. Better still, use one continuous strand of wire for the OWL and dipole leg.

  I posted earlier but dropped out a comment about my Elmer's antenna. He swore by the old spring-temper drawn telephone service cable. I knew him for nearly 50 years and never once saw any of his wire down.

 And, yes the BRONZE wire I referred to was indeed phosphor bearing bronze wire. We still have it here at work on some large spools.

The only time I ever saw #8 or #10 solid break from flexing was when a tree fell across it. My #10 open wire feedline has been up since '83. My reference 80 meter dipole has been up since '84.

So many great points made here...
In Venice Ca, we rarely have significant weather events that demand the kind of treatment that you East Coasters do. My first Butternut lasted 8 years with one set of guys (black Dacron) and worked great for what it was, but the salt air eventually devoured it.
I agree with Don's take on the split bolt or "Kerney" method of splicing or termination. Anytime you mix metals, electrolysis can be a real bitch, especially in salt water environments. I prefer that over solder under tension any day. To me, the reason why soldered terminations always break is because the copper becomes annealed with heat, and therefore loses it's structural strength.
 
I think I'll be fine using stranded wire  due to the WX associated with my QTH. The spreaders I plan to use are schedule 80 UV resistant sections of 3/8's PVC. As to pre stretching the wire, what method(s) do you guys propose? Does rigging up a temporary stretch in place jig, and leave it in place for a while sound right?

I actually hooked my wire that is still up for over 8 years to the back of my pick up truck ball hitch and a nearby tree and stretched it until it broke, and then spliced it back together. It was #10 stranded insulated wire.

I would like to see some scientific data on "pre-stretching" softdrawn stranded wire.

I also tried it years ago, and like Terry, found it stretched until it broke. (as expected) There must be a guideline, like stretch #10 wire  2% longer and then stop. 

Don't see a lot on the web about it from a short search.

So, what's actually happening - how is the wire changing its characteristics from a molecular point of view?  Does it actually get weaker as a result of the stretch, but have less tendency to stretch further from that point?

T

I think the key is the term  Hard drawn which might be misleading.

Just found this on the web
And this
When, however, the copper wire is intended to have a high tensile strength it is not annealed so frequently between the different drawings as in the case of iron.

Experiments have shown that the ductility of copper wire decreases as it tensile strength increases, but the experiments were not continued to an extent sufficient to show the exact ratio. A specimen of copper wire, thoroughly annealed, .128 inch in diameter, was found to have tensile strength of 330 lbs., and elongated 36 per cent. A sample of the same wire, on being drawn twice, to reduce its diameter to .104 inch, had a tensile strength of 330 lbs., and elongated 23 per cent. Another specimen, from the same piece, on being drawn thrice to bring it to the same diameter, namely .104 inch, was found to have a tensile strength of 415 lbs. and elongated but 3 per cent. Still another specimen from the same wire, drawn four times to reduce it to .104 inch, had a tensile strength of over 550 lbs. and elongated but 1 per cent. The average of a number of like experiments indicated that, in obtaining an elongation of 2.5 per cent. to 3 per cent., a reduction of 130 to 140 lbs. in the tensile strength would follow.

The term "hard drawn" is applied to distinguish the unannealed from the annealed copper wire; the only difference between soft copper wire and hard drawn copper wire being that one is annealed after drawing while the other is not. The process of drawing the wire through the die forms a thin, hard, polished crust, or shell, not exceeding the one thousandth of an inch in thickness, over the wire. Inside of this crust the metal is, seemingly, comparatively soft. The tensile strength of hard drawn copper wire appears to rest in this outside shell, for the lightest indentation made around the circumference of the shell with a sharp instrument will at once lower its breaking strain; and while, with an undented surface, the copper wire may withstand 5 or 6 bends on itself, with such a dent it will break in one bend. [/quote]

and they talk about broken wires in the process so the way we do it appears just fine.

I don't know anything about pre-stretching stranded wire. It does work with solid wire. I have done it a few times by trial-and-error: sometimes by hand, tying one end to a tree and the other end to a pipe or rake handle, and pulling with all my might. I was able to stretch a 100' length of #14 wire several feet that way. At first it stretches easily, but it quickly reaches a point where the stretch is no longer easy; I take that to be the limit of stretching, when most of the stretch is taken out of it. You can also tie it to a car bumper or trailer hitch or a tractor and the other end to a tree or utility pole, and use the vehicle to stretch, but it is easy to stretch it too much and break it if you are not careful.  A ratchet puller would probably work as well. Maybe there is a formula for the right amount of stretching. But for a serious antenna job I would still use copperweld, ready-made hard drawn wire, or phosphor bronze if I could find it.

I remember when I built my present radial system, which is made of #12 bare soft-drawn copper. I used a Mapp Gas torch and silver brazing rods to bond the radial wires to the common point. Right after the end of the wire was heated red hot and brazed to the copper strap at the tower base, as soon as it cooled down the wire would be extremely limp, almost as limp as a fabric rope or a strand of plastic cord.  But flexing it just a couple of times would restore it back to near its original stiffness.

As a practical matter, I lost about 15Kc in about two years from end-supported, #12 insulated stranded electrical wire originally cut for 3850Kc.  

I knew the wire had stretched, but didn't really measure the impact at RF until the "AM Bandwarming Party" when I wanted to see how bad my VSWR would be during the event.

Turns out the shift downward in frequency (from the longer physical wavelength of the doublet) was a happy thing.

I like copperweld for its long life and strength.   I have used flexweave and found that it frayed along edges of insulators.   It is good for a quick temporary antenna setup but avoid for any permanent antennas.   As with any exposed copper it is hard to resolder.

Yes, that was my main problem with Flexweave - how do you resolder it after it has been browned by the wx?  I tried sandpaper and even dipped it into Radio Shack circuit board etching solution. Both did not work well.

Don, I think your idea of stretching until most of the give is gone is a good idea. I remember feeling that point too. I'll bet a come-along is the best method.  

From Terry's info, maybe a target of 1-2% stretch is about right. That wud mean about  2.5' for a 125' wire for 2%.  The data shows it's quite an increase in strength when the wire is stretched. (330 lbs to 550 lbs!) That's the opposite of what I intuitively figgered.  Maybe the stretch tendency is arrested by the increased/improved tensile strength more than anything else.  I wonder what they mean by "drawn twice" or "drawn thrice?"  Do they draw it and wait for a minute then draw it again? What is the significance of doing it three times vs: once if the diameter is still the same .104" in this case?

Paul, from your data, looks like your dipole stretched about 5.75" to go from 3850 to 3835. Not bad, really.

T

The Navy used phosphor bronze for the long wires and lead-ins to the feedthru insulators into the radio rooms on upper levels or to 6" square conduits that ran thru the ship to the radio rooms and used solid #6 or larger copper wire for the inner conductor. Id guess the antennas were 5/16 cable and stretched tight 90' on the ship I was on; 2 on each side of center.

To connect the feeds to the antenna a pair of grooved phosphor bronze plates and 3/8" brass hardware were used. The plates had to be taken apart and wire brushed at least twice a year and the insides and wire were wire brushed.

While I was aboard for 2 1/2 years 1961-63 except a walkway between the pairs of midship towers was added before I arrived. Later a 35' whip was attached to the stack for the URC-32: http://www.bluejacket.com/usn/images/sp/a/ao109_waccamaw_a.jpg

After she got stretched:
http://en.wikipedia.org/wiki/File:USNS_Waccamaw_(T-AO-109)_1984.jpeg



Tom, dip it in a diluted hydrochloric acid, thoroughly wash, solder and then deflux. some splices done that way are holding up 30-40 years. I dont throw away useable wire :o

leftover network cable! often free, decently strong and flexible, can be sealed up decently, ties in knots well.. and it is free!

The sun will eat at the outer coating after a few years but a 150FT stretch of it is still up at an old farmhouse in Gainesville TX, works great for SWL but has seen the occasional transmitter.

I measured the thickness of the copper jacket on my #8.  I was a little disappointed that it measures only .012". But I used that wire for my beverage, which has been up for almost a decade now, and shows no sign of rusting through. I have pulled that wire tight several times with a fence wire tensioner, which has steel teeth to grip the wire, and although it gouged visible marks on the surface of the wire, it did not break through the copper jacket and no visible rust has appeared at the tooth marks, so the copper seems durable enough and resistant to deterioration in the weather. I'll look for a sample of the #10 telegraph line and see how thick the jacket on it is.

I suspect the stuff that rusted through was cheap electric fence wire, plated only a few molecules thick. Microscopic pores or cracks in the copper jacket allow moisture to enter and attack the steel core, and as the rust build-up it expands and pushes its way through to the outer surface.

My method for measuring the thickness of the jacket is as follows:

1.  Measure the diameter of a sample of the wire.

2. Using a small fine-toothed square or triangular file, file a flat spot on the wire, being careful to file only until the jacket is just barely filed through at one point and the steel core just begins to become visible. The visible steel should appear as a thin straight band parallel to the axis of the wire sample. If you see any more core than that, you have already filed too far.  Find another spot on the sample and repeat the above procdure.

3. Measure the diameter of the wire at the flat spot.

4. Subtract the above figure at (3) from that the original measurement (1).

Something else to consider with the Copperweld is whether or not the copper jacket is thick enough to allow the skin effect at the lowest frequency to prevent the rf from penetrating through to the steel and thus increase resistive losses.

We source our Copper coated wires from CommScope:
 http://www.commscope.com/company/eng/support_document/spec_sheets/bimetals/__icsFiles/afieldfile/2010/05/07/CCS40_0510_E.pdf

The coatings are applied is various thicknesses. They also supply Copper on Aluminum.
 A quick check on copper plated wire that they use in the lab here involves , I believe, Ferric Chloride. They quickly etch away the copper and measure the differences. This gives practical, usable readings on even the thinnest coatings.

  For larger areas , we use a Lamina Checker. It is a magnetic device that gives accurate measure of non ferrous coatings on a ferrous substrate.

   Adding a layer of Zinc plating between the steel core and copper jacket improves corrosion resistance by a large factor.

Don, I was wrong about the copper thickness, got that and conductivity mixed up.

Anyway this is from ATSM B452

.
The jacketed #12 Ive used in the past for Beverages and inverted vees for 160 was 30%. For 40% #8 it would be a minimum of .0116 and thats apparently what you have....good stuff.

My 160 wire verticals are stranded and jacketed #8 submerged well motor wire....tough stuff even outdoors for 20 years.

Does that 30% and 40% conductivity figure mean 30 and 40 percent the conductivity of solid copper?

Of course, the situation is totally different for RF, since the skin effect keeps most of the current close to the surface. In that respect, solid copper is a waste, and steel would do just as well (actually better, strength wise) in the core where there is little or no RF current flowing.

Another advantage of copperweld is that it is practically worthless to scrap  metal dealers. I have been told it brings even less than solid steel.  But the dumb-ass copper thieves probably wouldn't have a clue until they had already destroyed a radio installation, only to be told that their booty would bring them a tiny fraction of what they had anticipated.

That's what worries me about my heliax.  it is mostly plastic, foam and aluminum.  I guess the Al is worth something but the shield under the jacket makes it look like a big fat piece of copper (but lightweight so I hope that is a clue).

Commscope data reads. AC conductivity equal to copper >5 MC
 DC conductivity better than 39% for their 40% copper clad by weight product.


It is on the chart that comes with the link I referenced earlier. If you care to read it.

Don, the copper has to be real thin to affect 160 such as is on RG-6 copper clad steel and the skin depth isnt a concern on 80 and up. Solid copper RG-6 is available. With the commercial rural line cable its more than sufficient for 160, one of my 900' 2 wire Beverages is using it. Heck the others are using a copper/cadmium alloy and none require a preamp even way down at LF.

Since CATV only goes down to 5 MHz what happens lower isnt their concern but Ive measured a 500' hunk of 3/4" at 160 over 20 years ago and I needed a digital meter to measure...its that good.... but is copper over aluminum anyway.

Dirty Copper!

I use #12 THHN.

Mike WU2D

Antenna wax stops corrosion.

It will be interesting once I get the OWL going, to compare it to the RG-213. I will try to run it as flat as possible @ 438Ω out to the tuner complex at the tower.

When I first installed the antenna years ago I used military grade RG-214, doubly shielded and both braid and inner conductor silver plated. This was in the days when big dish satellite TV systems were in vogue; this same stuff was often used between the LNA at the focal point of the dish and the first stage of the receiver, located at minimum several feet away.  I figured that if it's good enough for microwave, it should be practically loss-free at 160m. I was disappointed when it measured only about 92% efficient.  Running 100 watts input to the line at the transmitter yielded about 92 watts at the other end of the 140' run.  

A few years later I checked it again, and the efficiency was way down, less than 80%.  That's when I discovered that rodents or other critters had chewed holes in the jacket allowing water to contaminate the coax.  I replaced it with direct-burial RG-213.  Again, the efficiency was up to about 92-93%.  A couple of years later, it had dropped to the mid-80s.  I didn't dig the  whole thing up, but did not find any holes chewed in the jacket this time, but looks like water still infiltrated it somehow. So much for running buried coax. I still had some left on the roll, so I replaced the buried run with an overhead run.

But even if OWL is 98% efficient, there is always loss in the matching network or tuner. A figure I have long seen tossed about is that the typical transmatch or tuner runs about 90% efficient (the Johnson KW Matchbox is supposed to be slightly better). The tank circuit in the transmitter should run about the same or maybe even less, since the ATU (tuner) typically runs at a lower loaded Q than does the tank circuit.

That's why I say that most hams have an inflated notion about their power output and the efficiency of their transmitter.  Let's say the final amplifier tube generates exactly 100 watts of steady carrier. The tank circuit losses reduce that to 90 watts. The tuner drops that another 10%, so the input to the feed line is 81 watts. Assuming the OWL is 98% efficient, about 79 watts actually make it to the antenna. The figure would be about the same with coax, if it is fed without a "transmatch", assuming the coax to be about 90% efficient. Using coax with a transmatch, lop off another 10% of the power to the antenna.

Assuming 75% efficiency at the class-C final per the tube data sheets, to generate 100 watts the transmitter runs 133 watts DC input. Therefore, taking into account plate tank circuit losses, antenna tuner losses and feedline losses, the total real efficiency of that same final (DC input to RF input to the antenna) is closer to 60% (54% with transmatch-coax combination), and that is a "best case". In the case of a "leen-yar", assuming 60% peak efficiency at the final tubes, the overall peak efficiency is closer to 48% (43% with transmatch-coax). And that's just at the peaks. The overall average efficiency is much lower, whether running AM or SSB.

Still, with a good antenna, a 20% reduction in power due to network and feedline losses will have a negligible effect on the signal at the other end, so this is largely much ado about nothing.

BTW, FWIW I ran across this article last night. A lot of interesting comments follow, both knowledgeable and clueless.

http://www.eham.net/articles/26162

He talked about "Far Field"  Never heard the term before. I guess I could look up what it means but I'll take the lazy approach and see if anyone one on here can tell me what it means?

Lots of math and fun can be thrown at this: but basically the Far Field is a point beyond which you are measuring far enough away from the antenna, that the power drops off in an exact inverse square manner with distance. Every time you double the distance between transmitter and receiver (in free space in the far field), you cut the amount of RF power received by four times. This is how you know you are actually in the far field.

In the Near Field, usually less than a couple of wavelengths away, the RF and the probe (or receiver and pickup antenna) are effected by all kinds of STUFF and Effects both known and unknown and it is harder to measure power accurately. Even comparative measurements are hard to make in the near field. This is why people use ammeters in the base of antennas. It is easier to make assumptions on power.

So to measure a bunch of 75 meter mobiles for a shootout, your pick up antenna should be no closer than several hundred feet away and it should be walked around a circle or several antennas should be switched in around a radius to average out effects. A half mile away would be a good distance! 

Actually, the inverse square law applies to three-dimensional space. Terrestrial propagation is essentially two-dimensional over the surface of the earth, so the drop-off more closely resembles a simple inverse function than it does to the inverse square law.

Ground wave signals propagate along the physical surface of the earth, making ground wave strictly two dimensional.  Sky wave propagation is ducted between the ionosphere and the ground via ionospheric refraction and ground reflection, making it also closely resemble two dimensional propagation, particularly as the distance away becomes large compared to the virtual height of the ionosphere.

Doubling the distance on the average would halve the signal strength, not reduce it to one fourth.  Of course it becomes more complicated than that with multi-path skywave and when skywave and ground wave propagation combine to produce skip zones and fading walls.

I doubt if any hammy hambone Class C amp is better than 70% and a Class B linear can reach 65 but 62 seems to be reasonable in a good design. Ole timey claims of 80-85% were due to a combination of assumed measurement accuracy mixed in with a bit of wacky tobacky.

In a pi net an incorrect value plate choke and insufficient C in the plate blocking cap can combine to eat up an easy 5%.

For any long outdoor run going to 50 or 75 Ohm hardline and good connectors eliminates the water migration and critter issue. I'll take my 450' run of 3/4" hardline over an OWL with a tuner any day.

The filament, screen, grid power, associated supplies and fans of big transmitting tubes doesn't help the efficiency situation either...

Taking it a step further, I am picturing the QIX-designed class E AM PDM rig.  One thing is for sure - when I run the 4X1 modulated by a pair, the room heats up. At the SAME RF power output, my class E 24 pill MOSFET PDM rig barely has an effect on room temp.  During the summer the e-rig is actually usable. The 4X1 is not. Noisy blowers too.

One obvious reason for less heat when using the e-rig is except for the low level 12V/24V  circuitry, there is no power being burned during standby. I key the HV supply - and there's no fils cooking.  In contrast, the 4X1's and associated supplies probably suck up 600w on standby.

But the other thing that is amazing is the RF output efficiency. I am seeing ~90% RF efficiency and >90% PDM modulator efficiency on the E rig.  The AM antenna on 75M is hardline feeding a 1/2 wave dipole, no tuner, just a coaxial choke - how more efficient can that be?

Should we regard the class E rig as an anomaly here?  Or should we just consider it "alien technology" and be done with it?  ;D     I just love coming into the shack, hitting three toggle switches and keying up a cool AM KW within seconds.  

Still, both rigs are fun.

T

That eHam article was readable but the comments reminded me of why I quit reading anything on eHam a few years ago.

Two omissions were (in my opinion) G5RV, and the frequent use of the term "resonance" by hams when referring to a 1:1 VSWR. 

The 3 filaments alone take about 475W. Add in the blowers, HV PS bleeders/equalizers that are always running, the transformer heating even in standby, the other PS in the rack and I bet they add an easy 3-400W more.


I dont discuss that mode in polite company ;D  Plus I operate all bands and QSY at will on any.

Now if you want cool (and quiet) than use that 3CW triode Ive mentioned; run it linear and scrap the mod deck.
The only difference you will notice is the AC meter outside spinning a little faster and on your bill ;D

Yep, maybe we are talking more like 900w on standby with the 4X1 - what a pig!    :o

The class E rig's limitation is QSY, though some have conquered that.  I am able to QSY from 3885 down to 3725 by just turning C1. (and the VFO, of course)  It puts out full power there and the waveform looks FB.  But it is a one band rig for 75M.

Others just use the same infrastructure and switch in a different RF deck. Pretty easy. Still, others are switching bands using little high-curent relays to add padding caps, etc. I know of at least three that do 160/75/40M with a flick of the switch.   However, 20-10M is still limited by the MOSFET devices not being cheap.

With the new VFO/digital drive system, the overall RF deck has become quite stable and indestructable. Even I haven't lost an RF strip yet in 18 months of opertation. That's saying something... ;D

T

It might be useful on 600M, can they handle CW and data modes as well as AM and SSB?

And that is AWESOME !

Carl,

On the VLF bands the guys appear to favor the class D rigs over the E rigs for digital/cw modes.  The layout is simpler for class D and QSYing is just like using a class C rig.  Jay/W1VD is the guy to axe about this.  I'm not sure if he has ironed out issues related to combining class D modules yet. Some of the big logs are running serious power up there solid state.

Steve/QIX favors the class E rig for HF. I don't recall the reasons why over class D, though Jay has an excellent sounding class D 300w? AM rig on HF.

I don't see why a class E rig cannot handle any signal application related to non-linear operating, like digital, CW, FM, etc.  AM requires a PDM or analog modulator. SSB would be a problem since it would need a linear amplifier or digital switching scheme of some kind.

T

I haven't had breakage with a #13 copper covered steel with insulation.It is available from the Wireman and others....Lee,N2UDF.