LAYING RADIALS FER A VERTICAL

[K5UJ]

Lots of interesting comments.  Radials are one of those topics hams will dissect and chew on to the end of time.  There have been a zillion studies done, each one examining radials from one point or another, and now all these articles based on modeling, so everyone can dig up something to prove his point.  When I was getting ready to set up my inverted L on 160, I spent some time gathering as much radial literature as I could find, and I read it all, looked at all the plots, and so on, and finally it all seemed to boil down to put as may down as you can, fitting them in your lot lines as best as possible, and operate.  Some will tell you to put a feedline common mode choke out at the feedpoint.  I found it unnecessary if you have enough radials, for the return current will divide up enough so the amount on the feedline shield is minimal.

The whole deal with RF exposure on any frequency that won't cause thermal heating is total B.S.   RF is non-ionizing radiation.  It cannot break dna bonds.  the RF exposure nonsense is just politics.  It has a point only if you want to walk out in front of a microwave dish emitting a high strength uwave field for troposcatter but you don't want ur eyeballs turned into hard boiled eggs.   Guys spend careers out at HF bc station tx sites, medium wave 50 kw sites, up on top of Sears, Hancock and Empire under millions of watts ERP of FM and TV with no problems.  

I used to think 120 radials was the gold standard, but that number is a FCC requirement and bc stations go along with it because it allows for an easier more expeditious (i.e. cheaper) proof of performance.

on high bands I'd tend to go with elevated radials; on 160 the problem is getting them elevated enough to work as elevated radials are supposed to.  hence, lots of radials on the ground (unfortunately, because they cost more).  

Clark, the ground conductivity in AZ is such that you will realize a significant transmit efficiency improvement with the addition of around 50 more radials.  you may not notice anything on rx, and listeners may not always give expected reports because of other variables such as propagation (keep in mind that even 50 kw stations on skywave sometimes come in lousy) but the money for the wire over time will be money well spent.  If you plan to be at ur QTH for several years, I'd invest in no. 14 solid insulated in 500 foot rolls.  too many radials means if a few get broken it's no big deal so don't think ur wasting money by putting down around 60.  Also no. 14 with the insulation on it is pretty strong and lays down easy.

73

rob / k5uj


photo below of my latest feedpoint tuner on 160:  

[k4kyv]

Excellent articles on radials in the last four issues of QEX.  Rudy Stevens, N6LF, built a test range and meticulously measured performance of various numbers, lengths and heights of radials...
I don't have this series of four articles in electronic format and I don't know if the ARRL does either.  They were in the last four issues of QEX, 251,252,253,254.

A crying shame those articles weren't published in QST, which has turned into a worthless POS and waste of trees.

[Ian VK3KRI]

One thing I've see in print a few times is that if you use a folded feed on a vertical (like half a folded dipole) you increase the impedance which reduces the losses  because the ratio of ground resistance to radiation resistance is reduced.
(eg Radio Handbook 19th ed p25.6)

I can't see how that could possibly be. Surely the the impedance that is stepped up IS  the real radiation resistance + ground losses and the ratio just stays the same?
                                                                                     Ian VK3KRI
 

[Steve - WB3HUZ]

No free lunch. The equivalent ground loss resistance is stepped up too.

[k4kyv]

Or you can think of the folded unipole system as a step-down impedance transformer between the feed line and the vertical.  The impedance of the vertical radiator is still the same, but the feedline sees 4X the base impedance.

[flintstone mop]

This is a very nice thread indeed. I have had good commo with Walt.  And even though I am on a 1.1 acre lot, running .4 wavelength long radials would be a hassle to manage and the cost involved, even buying "surplus wire".
So, I would have to get as many as I can afford around the base of my shortened vert.
 
When I first moved here, I ran a long wire (600ft) beverage on the ground, on what I thought was not intruding on anyone. I figured, "who walks back here"?  By Spring time the wire was all rolled up in a pile on my property.

And Rick.....I wish wire was that easy to get. Although I have never looked in Lowes. I have to dig around the Internet for Surplus Wire to find something reasonable.

Fred

[k4kyv]

Think of the folded unipole as two vertical elements mounted side by side in close proximity, and connected together at the top.  The whole thing acts like a fat single vertical element, and at a quarter wavelength and lossless ground system, ideally the base impedance should be 36 ohms at resonance.  If you tie both elements together at the base and series feed them, the rf current will be equally divided between both elements so that each one runs half the total current. Now disconnect the elements from each other at the base, and feed only one of them, while connecting the other one directly to ground.  The driven element still carries half the total base current, but according to P=I^2 x R, to achieve the same power level at half the current, the load impedance at the driven element has to be four times the original base impedance, theoretically somewhere around 144 ohms.  But the  radiation resistance is still 36 ohms.  However, the tuning network may be able to work into a 144-ohm load with a little less loss than it would into a 36-ohm one.

[W2DU]

As usual, Don is right on the money in his explanation of the folded unipole.

However, the following is a quote from my earlier post:

Now for everyone: I'll be pleased to email a copy of the entire BL&E IRE paper to anyone who'd like it, but please request it by email to me at walt@w2du.com. The paper is in the Proceedings of the IRE, Volume 25, No. 6, June 1937.

So far, only two have requested a copy of the BL&E paper that is the basis for the FCC requirement for radials that go with AM BC radiators, which has also become the worldwide standard. The paper delves deeply into both the theoretical basis for its statements and the reporting on many, many individual experiments which verify the theory.

In case my original offer was overlooked, for those interested my offer is still in effect.

I'm also pleased to tell you that the 'E' in BL&E was Jess Epstein, who was one of my engineering colleagues at the antenna lab of the RCA Laboratories, aka the David Sarnoff Research Center at Princeton, NJ.

[W2DU]

Fred, I often hit the 'post' button before I said everything I wanted to say. My last post above is an example.

What I intended to say is to iterate Don's much earlier statement, that if the radials have to be short there should be lot of 'em, because the highest ground currents occur within the area nearest the vertical radiator.

Did you ever find out who rolled up your radials? Perhaps some squirrels?

Walt

[flintstone mop]

Walt, there was a human involved rolling up the wire. I "ASSumed" that it was ok to run this wire on someone elses's property.

Rob, I like your tuner design, it gave me ideas for mine. Hoping to be remote controlled with some DC motors to tune capacitance and inductance. Slide up and down 160 and who knows where else.
I hope in the next month it will be up and running for the 160M. I have to get back into the radio mode. Tooo many things right now.

The #14 solid wire might not "disappear" as easily as my discovery with #24 stranded. I'm guessing you do not have to mow very much in your neck of the woods?

Fred

[K5UJ]

Walt, there was a human involved rolling up the wire. I "ASSumed" that it was ok to run this wire on someone elses's property.

Rob, I like your tuner design, it gave me ideas for mine. Hoping to be remote controlled with some DC motors to tune capacitance and inductance. Slide up and down 160 and who knows where else.
I hope in the next month it will be up and running for the 160M. I have to get back into the radio mode. Tooo many things right now.

The #14 solid wire might not "disappear" as easily as my discovery with #24 stranded. I'm guessing you do not have to mow very much in your neck of the woods?

Fred

Hi Fred,  Thanks--the ceramic caps are overkill but they were what I had on hand.  I bought about 30 of them at a hamfest a few years ago for 1 or 2 dollars each.  There are four 500 pF and two 250 pF.  The 250s can be clipped in and out (the bluegreen ones).  That tuner can probably handle twice the power I'll give it at least, before the cap arcs.  If you build something similar just make sure the inverted L wire is at least 1/4 wave on the lowest part of 160 you want to operate otherwise you'll start loosing a lot of power in the inductor.   Mine is cut for the middle of the band so if I tune it down around 1840 the inductor dissipates 40 watts for 1200 w. going into the tuner (according to TLW modeling). 

I have to mow; I'm right in town (unfortunately) but what I do is raise the blade on the mower as high as it will go.  At the start of each mowing season I sharpen the blade.  If you do hit a wire with it, you want the blade to slice it, otherwise it will wrap it up.   Clipping a radial in two is a lot easier to repair.  If you have grass your wire will disappear into the ground surprisingly fast.  I even have 1/2 inch hard line sinking into the ground.  I can mow right over it, walk on it, run the mower over it--it's mostly invisible now. 

73

rob k5uj

[ve6pg]

..wow...lots of gud stuff..ok...how about a multi-band vertical?...
..in other words, would it work, it a guy was to take 5 different lengths of wire, say, for 160/75/40/30/20 (1/4 wave), attach them at the ground feed point, but have them "bunched" together?...so, you would have multiple lengths, in one wire run?...i would use many of these, kinda like 5 conductor rotor cable, having the longest fer 160, es the shortest fer 20..but understand, this would not be only one run of wire, but many, fanned-out from the vertical....

..tim..

...sk..

[KD6VXI]

..wow...lots of gud stuff..ok...how about a multi-band vertical?...
..in other words, would it work, it a guy was to take 5 different lengths of wire, say, for 160/75/40/30/20 (1/4 wave), attach them at the ground feed point, but have them "bunched" together?...so, you would have multiple lengths, in one wire run?...i would use many of these, kinda like 5 conductor rotor cable, having the longest fer 160, es the shortest fer 20..but understand, this would not be only one run of wire, but many, fanned-out from the vertical....

..tim..

...sk..

The ARRL manual and one of Orr's books both describe using rotor control wire as you talk about.

Both the 4 wire flat pack crap, as well as the rounded 8 conductor.

--Shane

[ka3zlr]

Copper's down get it down soon, before it climbs back up....

73
Jack.

[k4kyv]

When I first moved here, I ran a long wire (600ft) beverage on the ground, on what I thought was not intruding on anyone. I figured, "who walks back here"?  By Spring time the wire was all rolled up in a pile on my property.

At least they rolled it up and didn't just leave a tangled mess, and piled it on your property instead of throwing it in the trash. 

[ke7trp]

The meth heads climbed my fence and stole two aluminum 10 meter verticals, and all my wire.  I turned on the station and could not hear anything. I went back there and found all the wire gone.  Lucky for us they really started cracking down on stealing wire. The sad thing is that what they stole they probably got $20 for.

Clark

[KD6VXI]

The meth heads climbed my fence and stole two aluminum 10 meter verticals, and all my wire.  I turned on the station and could not hear anything. I went back there and found all the wire gone.  Lucky for us they really started cracking down on stealing wire. The sad thing is that what they stole they probably got $20 for.

Clark

Even more sad, one of the antennas you had stolen was retailing last week for almost 400 dollars!

20 to 1 profit to loss margin

--Shane

[ke7trp]

That antenna never worked right. Thats why it was down. The guy built the gamma match network using RG213 coax of 50ft. If you used anything else, It would not match.  The direct input was something like 20 ohms and the bandwidth was like 100KC. After talks with him I realized that he did not understand that the antenna should be tuned.. not the coax and the antenna.

Clark

[Jeff W9GY]

I've used a lot of galvanized electric fence wire to augment the copper I have.  Lay it out in late fall, and staple it down using staples made of clothes hangers bent in a "U".  Don't use the Chinese wire, it's crap and is very poorly galvanized.   Oklahoma Steel and Wire which makes good stuff -- a sample of which I've had outdoors for two years now and no rust showing.  Come spring, when the grass starts growing, the wires dissapear and all is well.  Add some more again in the fall.

[flintstone mop]

hey Rob,
Nothing wrong with overkill using ceramic caps. The RF voltages can get extremely high.
During my rich days I glawmed onto a couple of vac variables. I made contact with a machinist and incorporated a automobile door window motor to drive the vac variable in a my future tuner adventure. I hope I can finalize and connect by August.
The Galvinized aluminum is for very patient people. Very un-cooperating and easily chopped up in mowing season, if your don't staple it down every 4 feet.
UN-fortunately that great Shadio Rack Rotor wire is no longer available. That was a neat way to get a bunch of wire down in a short time.


And Don, I have had people tell me that laying a wire around their property is an invasion of their privacy. Like I can hear what is going on in their house by laying a wire near it. WOW oooohhhh they're comming to get me.........

fred

[KD6VXI]

UN-fortunately that great Shadio Rack Rotor wire is no longer available. That was a neat way to get a bunch of wire down in a short time.

fred

Senor Mop...

I, too, found the loss of Radio Shack wire.  I, too, found a replacement!

Sprinkler timer wire from Home Cheapo or Lowes!  I even found some that had 2 wires heavier gauge (for the motor of the rotor), and the signal wires where about 3 or 4 sizes smaller.

Was slightly more 'spensive, BUT a LOT better insulated.  I think it was only slightly more 'spensive, but not much.

You have to watch out, though, how many stations it's advertised for......  Each station gives you a pair of wires.....  Nuff said!

I'm using 50 feet of it now....  4 conductors used for the remote Tuna (an Icom clone), and 3 leads for the remote wattmeter. 


--Shane

[flintstone mop]

Senor Mop...

I, too, found the loss of Radio Shack wire.  I, too, found a replacement!

Sprinkler timer wire from Home Cheapo or Lowes!  I even found some that had 2 wires heavier gauge (for the motor of the rotor), and the signal wires where about 3 or 4 sizes smaller.

Was slightly more 'spensive, BUT a LOT better insulated.  I think it was only slightly more 'spensive, but not much.

You have to watch out, though, how many stations it's advertised for......  Each station gives you a pair of wires.....  Nuff said!

I'm using 50 feet of it now....  4 conductors used for the remote Tuna (an Icom clone), and 3 leads for the remote wattmeter. 


--Shane

[/quote]

THANK YOU Shane. GUD info

Fred