Topband: Topband Digest, Vol 113, Issue 6

Sat May 5 06:57:54 PDT 2012

Keep in mind this Sole purpose of a BC station is to get coverage of about 60 miles running 5KW day time and 1 KW night time with no fad and quality signal not to work DX.

I read in some posts or on some web site that it does not matter if the ends are tied to a ground rod or not.  Note then ends not at the base of the vertical.

My backyard is only 35 by 36 feet.  You guys only think you have a small back yard.  Compare it with this one.

The City water pipe system sure works as the good ground I guess so does the neighbors plumbing cause their house in only 8 feet from mine :-)

Jim K9TF Stay on course, fight a good fight, and keep the faith.  Jim K9TF/WA9YSD

________________________________
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Sent: Saturday, May 5, 2012 7:07 AM
Subject: Topband Digest, Vol 113, Issue 6

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Today's Topics:

   1. Re: Fwd: radals fer 160m vertcal (Richard Fry)
   2. Re: Fwd: radals fer 160m vertcal (James Rodenkirch)
   3. Re: Fwd: radals fer 160m vertcal (Jim Brown)
   4. Re: Fwd: radals fer 160m vertcal (BP Veal)
   5. Re: Fwd: radals fer 160m vertcal (Merv Schweigert)
   6. Re: Fwd: radals fer 160m vertcal (W2RU - Bud Hippisley)
   7. Re: Fwd: radals fer 160m vertcal (Joe Subich, W4TV)
   8. Re: Fwd: radals fer 160m vertcal (Richard Fry)

----------------------------------------------------------------------

Message: 1
Date: Fri, 4 May 2012 19:10:56 -0500
From: "Richard Fry" <rfry at adams.net>
Subject: Re: Topband: Fwd: radals fer 160m vertcal
To: <topband at contesting.com>
Cc: rfry at adams.net
Message-ID: <CBE6FE690AFC41169BDC2A6EAB2A6EA2 at RFryNew530>
Content-Type: text/plain; format=flowed; charset="Windows-1252";
    reply-type=original

Bud, W2RU wrote:

> 3.  Using radials that are longer than a vertical (of reasonable 
> electrical length) is tall simply wastes a lot of money (and real estate).

Those tending toward such beliefs should be interested in the clip at the 
link below, as well as the BL&E study linked earlier in this thread.

Note the logical conclusions therefrom that the radiation efficiency of 
every vertical monopole system of every electrical height depends on the 
loss of the r-f ground reference against which it is driven.

These data show that for monopole heights no matter how short in electrical 
wavelength, system radiation efficiency using buried radials is dependent on 
the r-f loss in the circular surface area at/just below the surface of the 
earth within ~1/2-wavelength radius of such monopoles.

In fact, the shorter the electrical heights of such monopoles, the more 
important such r-f loss becomes toward defining the radiation efficiency of 
those electrically short monopole systems.

http://i62.photobucket.com/albums/h85/rfry-100/GroundCurrentNearMonopole.gif 

------------------------------

Message: 2
Date: Fri, 4 May 2012 18:52:38 -0600
From: James Rodenkirch <rodenkirch_llc at msn.com>
Subject: Re: Topband: Fwd: radals fer 160m vertcal
To: <rfry at adams.net>, <topband at contesting.com>
Message-ID: <SNT137-W50C637D82A7B7BB29CC47BF02D0 at phx.gbl>
Content-Type: text/plain; charset="iso-8859-1"

What about radials above the ground?  Like what I'm planning to install --- base of the vertical at around 5' to 6' above ground and slope all of the radials from that 5' or 6' point down to the ground?  Jim R. K9JWV

> From: rfry at adams.net
> To: topband at contesting.com
> Date: Fri, 4 May 2012 19:10:56 -0500
> CC: rfry at adams.net
> Subject: Re: Topband: Fwd: radals fer 160m vertcal
> 
> Bud, W2RU wrote:
> 
> > 3.  Using radials that are longer than a vertical (of reasonable 
> > electrical length) is tall simply wastes a lot of money (and real estate).
> 
> Those tending toward such beliefs should be interested in the clip at the 
> link below, as well as the BL&E study linked earlier in this thread.
> 
> Note the logical conclusions therefrom that the radiation efficiency of 
> every vertical monopole system of every electrical height depends on the 
> loss of the r-f ground reference against which it is driven.
> 
> These data show that for monopole heights no matter how short in electrical 
> wavelength, system radiation efficiency using buried radials is dependent on 
> the r-f loss in the circular surface area at/just below the surface of the 
> earth within ~1/2-wavelength radius of such monopoles.
> 
> In fact, the shorter the electrical heights of such monopoles, the more 
> important such r-f loss becomes toward defining the radiation efficiency of 
> those electrically short monopole systems.
> 
> http://i62.photobucket.com/albums/h85/rfry-100/GroundCurrentNearMonopole.gif 
> 
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK

------------------------------

Message: 3
Date: Fri, 04 May 2012 18:34:31 -0700
From: Jim Brown <jim at audiosystemsgroup.com>
Subject: Re: Topband: Fwd: radals fer 160m vertcal
To: topband at contesting.com
Message-ID: <4FA483A7.9070305 at audiosystemsgroup.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

On 5/4/2012 5:52 PM, James Rodenkirch wrote:
> What about radials above the ground?  Like what I'm planning to install --- base of the vertical at around 5' to 6' above ground and slope all of the radials from that 5' or 6' point down to the ground?

N6LF has published extensive work that he did on 40M showing that 
radials elevated only a feet or so were quite effective, and that a foot 
higher was better, but close to many radials on the ground.  I tried 
scaling this to 160M, placing radials at about 5 ft.  They were NOT 
particularly effective, and I had the chance to discuss the issue with 
N6BT, who has studied elevated radial systems extensively on 160M.  
Paraphrasing Tom, the earth at 160M is a rather different animal than it 
is at 40M.  Tom suggested that 16 ft was a better height for a few 
elevated radials on160M, and I hope to move the ones on my experimental 
antenna to that height in the next month or so, perhaps even before 
leaving for Dayton.

73, Jim K9YC

------------------------------

Message: 4
Date: Fri, 4 May 2012 19:56:24 -0600
From: BP Veal <bryonveal at msn.com>
Subject: Re: Topband: Fwd: radals fer 160m vertcal
To: <jim at audiosystemsgroup.com>, "topband at contesting.com"
    <topband at contesting.com>
Message-ID: <SNT143-W49AC316E9884265A926EBAB32D0 at phx.gbl>
Content-Type: text/plain; charset="iso-8859-1"

Gull Winged raised radials cut to resonance seem to be excellent above ground radials-  But I am in a small yard, and have my MA160V hooked up to radials going all over the yard, buried, of various lengths, 10-80 feet, about 60 of them- it only goes out in about a 100 degree pattern as the antenna is in the corner of the yard-they work as the resonance point and SWR bell curve really are effected when they are hooked up-  15KHz of usable bandwidth at a 4:1 SWR (matched with an UnUn to 1.5:1) vs 60KHz bandwidth without the radials at a 1:1.2 SWR, reflective of the hidden ground loss and impendence mismatch- -  so even in a puny yard, with limited space, measured effect of buried radials can be significant.......too many dogs and kids for raised radials.......

Bryon "Paul" Veal  MAED
FCC Amateur Radio License-N0AH
n0ah at arrl.net
Home Page at http://groups.yahoo.com/group/HamRadioPropagation/

> Date: Fri, 4 May 2012 18:34:31 -0700
> From: jim at audiosystemsgroup.com
> To: topband at contesting.com
> Subject: Re: Topband: Fwd: radals fer 160m vertcal
> 
> On 5/4/2012 5:52 PM, James Rodenkirch wrote:
> > What about radials above the ground? Like what I'm planning to install --- base of the vertical at around 5' to 6' above ground and slope all of the radials from that 5' or 6' point down to the ground?
> 
> N6LF has published extensive work that he did on 40M showing that 
> radials elevated only a feet or so were quite effective, and that a foot 
> higher was better, but close to many radials on the ground. I tried 
> scaling this to 160M, placing radials at about 5 ft. They were NOT 
> particularly effective, and I had the chance to discuss the issue with 
> N6BT, who has studied elevated radial systems extensively on 160M. 
> Paraphrasing Tom, the earth at 160M is a rather different animal than it 
> is at 40M. Tom suggested that 16 ft was a better height for a few 
> elevated radials on160M, and I hope to move the ones on my experimental 
> antenna to that height in the next month or so, perhaps even before 
> leaving for Dayton.
> 
> 73, Jim K9YC
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK

------------------------------

Message: 5
Date: Fri, 04 May 2012 16:01:34 -1000
From: Merv Schweigert <k9fd at flex.com>
Subject: Re: Topband: Fwd: radals fer 160m vertcal
To: topband at contesting.com
Message-ID: <4FA489FE.4040908 at flex.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

At my old QTH in ILL,  I used a fed tower with 4 elevated radials,  they 
were about
12 foot off the ground,  it worked fairly well,  but I started adding 
radials on the ground,
as I added radials the feed point impedance changed,  I hit diminishing 
returns at about
60 radials,   the difference between 4 elevated and adding the 60 on the 
ground was
more than the equivalent of doubling my power.   so at least 3DB for 
me.  YMMV..
The raised radials were very "hot"  I could draw a 2 to 3 inch spark off 
the ends
easily so make sure they are insulated and out of reach of humans.
Almost set my garage on fire as one radial arced over to the roof 
flashing close to where
it was tied off.

I find a big difference in 160 compared to a 4 radial GP type system on 
40 meters,
maybe if the radials were much higher and less coupling to the ground 
they would work
better.
73 Merv K9FD/KH6   KH7C

> On 5/4/2012 5:52 PM, James Rodenkirch wrote:
>    
>> What about radials above the ground?  Like what I'm planning to install --- base of the vertical at around 5' to 6' above ground and slope all of the radials from that 5' or 6' point down to the ground?
>>      
> N6LF has published extensive work that he did on 40M showing that
> radials elevated only a feet or so were quite effective, and that a foot
> higher was better, but close to many radials on the ground.  I tried
> scaling this to 160M, placing radials at about 5 ft.  They were NOT
> particularly effective, and I had the chance to discuss the issue with
> N6BT, who has studied elevated radial systems extensively on 160M.
> Paraphrasing Tom, the earth at 160M is a rather different animal than it
> is at 40M.  Tom suggested that 16 ft was a better height for a few
> elevated radials on160M, and I hope to move the ones on my experimental
> antenna to that height in the next month or so, perhaps even before
> leaving for Dayton.
>
> 73, Jim K9YC
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
>    

------------------------------

Message: 6
Date: Fri, 4 May 2012 23:28:57 -0400
From: W2RU - Bud Hippisley <W2RU at frontiernet.net>
Subject: Re: Topband: Fwd: radals fer 160m vertcal
To: Richard Fry <rfry at adams.net>
Cc: topband at contesting.com
Message-ID: <5B6216B7-01CF-4071-8C5D-AEBA4DE750F9 at frontiernet.net>
Content-Type: text/plain; charset=windows-1252

On May 4, 2012, at 8:10 PM, Richard Fry wrote:

> Bud, W2RU wrote:
> 
>> 3.  Using radials that are longer than a vertical (of reasonable 
>> electrical length) is tall simply wastes a lot of money (and real estate).
> 
> Those tending toward such beliefs should be interested in the clip at the 
> link below, as well as the BL&E study linked earlier in this thread.

I think you missed the parenthetical portion of my sentence:  "of REASONABLE electrical length".

> Note the logical conclusions therefrom that the radiation efficiency of 
> every vertical monopole system of every electrical height depends on the 
> loss of the r-f ground reference against which it is driven.

No argument there.  The ground losses and the radiation resistance of the vertical monopole form a voltage divider.  The higher the radiation resistance of the monopole itself, the greater the percentage of transmitter power that is radiated, rather than being dissipated in heating up the ground near the monopole.  The "logical conclusion" (to borrow a phrase) to take from this is that you can spend a whole lot more of your time getting on the air and actually working far away stations and a lot less time fussing with your radial field, transmission line connections, etc., if you first put your effort into making your vertical monopole as close to a quarter-wave in height as you possibly can.

> These data show that for monopole heights no matter how short in electrical 
> wavelength, system radiation efficiency using buried radials is dependent on 
> the r-f loss in the circular surface area at/just below the surface of the 
> earth within ~1/2-wavelength radius of such monopoles.

Agreed.  But as I attempted to explain in my previous posting by using the examples I took from the two curves you pointed us to, for a REASONABLE electrical height (say, 75 degrees), the difference between quarter-wave and half-wave radials is hardly earth-shattering (pardon the pun).  

The thrust of the paper you were referencing was that the AM broadcast industry, which had been fixated on half-wavelength vertical radiators since its inception, could attain comparable field strengths with vertical radiators as short as an eighth-wavelength (45 degrees' electrical height) if reasonable attention was given to the radial fields beneath them. 
What was absent from the paper, however, was any concern for losses in the matching network between the transmitter and the base of the antenna.  All the curves, and all the comparisons in that paper are based on constant power to the base of the antenna ? NOT constant power at the output of the transmitter!  Only at the very end of the paper is it noted that the added cost of low-loss inductors for the matching network can be paid for out of funds saved by constructing a shorter tower....:-)  AM broadcast stations are governed by a different set of regulations than amateurs.  I'll try your approach provided I'm free to run as much transmitter power as I need in order to deliver a solid 1500 watts to the base of a very short vertical.

Furthermore, you neglected to mention the curve in that same article that shows how a 25-degree tall tower, for example, has more than 20 times the peak voltage across the base insulator than a 75-degree tower does.  The difference in insulator specifications required by those two towers represents a potential cost increase (or, at the very least, an increase in the mechanical complexity of the vertical at its base) that is totally unnecessary if appropriate techniques are used to maximize the electrical length of the vertical portion of the antenna. 

> In fact, the shorter the electrical heights of such monopoles, the more 
> important such r-f loss becomes toward defining the radiation efficiency of 
> those electrically short monopole systems.

Gosh, that was my point, I thought.

One of the core things you learn in any course on antennas is that there's only a fraction of a dB difference in the theoretical gain of a half-wave dipole or quarter-wave monopole versus an infinitesimally short one FOR EQUAL FEEDPOINT DRIVE, but I'll always choose to put my effort into erecting the full half-wave dipole or the full quarter-wave monopole.  Why?  Because I know the difficulty and the losses I'll encounter trying to match the 50-ohm output of my transmitter to the extremely low resistive and extremely high reactive input impedance of an infinitesimally short wire ? especially if I'm limited to AFFORDABLE matching network components.  I have a good friend struggling with that exact issue right now; he has an (expensive) antenna coupler that claims to be capable of handling 1500 watts.  It also claims to be able to handle SWRs up to such-and-such.  What the specs don't say, however, is that it can't do both simultaneously.  Components
 melt if my friend tries.  Antenna m
atching units that can deliver 1500 watts of RF to high SWR feedpoints are neither simple nor inexpensive.  By and large, they are far beyond what most amateurs are willing or able to spend.

Losses in the ground are only one part of the resistance divider equation.  Six ohms' ground loss (as measured by at least one person on here) is far less important to a vertical that has an input impedance (over perfect ground) of 37 ohms than it is to a very short vertical with an input impedance of 1 ohm.  What the Brown article neglects is that similar or higher losses in the matching network are equally destructive to the performance of very short verticals.  You can have a very short vertical attached to a perfect ground extending for miles in all directions, and still get lousy performance because you can get only a fraction of the transmitter output power into the radiation resistance of the vertical.  The beauty of striving for the maximum electrical height possible at your specific installation is that you are reducing the effect of BOTH kinds of losses!

My comments were directed at those of us who are interested in vertical monopoles as a means to an end ? working far away stations.  I tend to work more stations by sitting in front of my rig than I do if I'm spending hours carting instrumentation (that I can't afford) around the back yard or burying 50-100% more wire for questionable benefit.   Is my 160-meter shunt-fed vertical with 16 radials of various lengths perfect?  No.  Do I have highly conductive ground around it?  Heck, no!  Is it a full 90 degrees' electrical wavelength?  Thanks to the top-loading of my HF Yagis, it's pretty close.  Does it get out well?  You better believe it!  Could it get out better?  Sure...for that 0.01% of the time I can't get through to the DX.

To repeat:  In my opinion, for amateurs to lose a lot of sleep over whether to have quarter-wavelength or half-wavelength radials beneath a vertical monopole of REASONABLE electrical length is foolish. 

I stand by my earlier comments.

Bud, W2RU

------------------------------

Message: 7
Date: Sat, 05 May 2012 01:38:08 -0400
From: "Joe Subich, W4TV" <lists at subich.com>
Subject: Re: Topband: Fwd: radals fer 160m vertcal
To: topband at contesting.com
Message-ID: <4FA4BCC0.8020900 at subich.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

On 5/4/2012 10:01 PM, Merv Schweigert wrote:
> I find a big difference in 160 compared to a 4 radial GP type system
> on 40 meters, maybe if the radials were much higher and less coupling
> to the ground they would work better.

Purely on a logical basis there are two factors working against the
(sparse) elevated radials on 160 meters vs. 40 meters.  First the
160 meter radial system is 1/4 as high in terms of wavelength than
the 40 meter system  ... that means fields in the (lossy) dielectric
are 16 times greater.  Secondly, the skin depth is much greater on
160 than on 40 meters meaning there is greater volume of dielectric
to generate losses.

I don't have the tools to really calculate the difference but I would
postulate that the dielectric (ground) losses increase at some rather
high exponential (perhaps as the square squared) rate as frequency
decreases.  When this is coupled with "short" radial systems - even
those that are "dense" close to the antenna or dense in only one sector,
the losses can really get out of hand.

73,

    ... Joe, W4TV

------------------------------

Message: 8
Date: Sat, 5 May 2012 07:07:11 -0500
From: "Richard Fry" <rfry at adams.net>
Subject: Re: Topband: Fwd: radals fer 160m vertcal
To: <topband at contesting.com>
Message-ID: <5D3B3E458E9241ED8CB11A80C7407857 at ToshLaptop>
Content-Type: text/plain; format=flowed; charset="Windows-1252";
    reply-type=original

James Rodenkirch wrote:
>What about radials above the ground?

This link http://www.commtechrf.com/documents/nab1995.pdf leads to a paper 
by Clarence Beverage with some real-world results for monopoles with 
elevated wires used as a counterpoise.   Here is a quote from it:

\ \The antenna system consisted of a lightweight, 15 inch face tower, 120 
feet in height, with a base insulator at the 15 foot elevation and six 
elevated radials, a quarter wave in length, spaced evenly around the tower 
and elevated 15 feet above the ground. The radials were fully insulated from 
ground and supported at the ends by wooden tripods.

Power was fed to the system through a 200 foot length of coaxial cable with 
the cable shield connected to the shunt element of the T network and to the 
elevated radials. A balun or RF choke on the feedline was not employed and 
the feedline was isolated from the lower section of the tower. The system 
operated on 1580 kHz at a power of 750 watts.

The efficiency of the antenna was determined by radial field intensity 
measurements along 12 radials extending out to a distance of up to 85 
kilometers. The measured RMS efficiency was 287 mV/m for 1 kW, at one 
kilometer, which is the same measured value as would be expected for a 0.17 
wave tower above 120 buried radials. / /

So while such "elevated" installations are rare for AM broadcast stations, 
their performance has been measured to be about the same as when using an 
r-f ground consisting of 120 buried wires, each 1/4-wave long (free space 
length).

These elevated systems are readily modeled using NEC-2.  However the 
radiation patterns shown by a typical NEC far-field analysis do not 
accurately show the fields actually "launched" by them, or by any vertical 
radiator with its base near the earth, because they do not include the 
surface wave.

The fields radiated in and near the horizontal plane by any vertical 
monopole of 5/8 wavelength height and less are the greatest fields it 
radiates in the entire elevation plane, regardless of earth conductivity. 
Those fields from very low elevation angles (say, less then 5 degrees) can 
reach the ionosphere, and under the right conditions return to the earth as 
a useful skywave.

The link below illustrates this concept.

http://i62.photobucket.com/albums/h85/rfry-100/Space_Surface_Wave_Compare.gif

------------------------------

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End of Topband Digest, Vol 113, Issue 6
***************************************