The AM Forum

 Dear friends,

I lived in Indonesia,I've made small medium radio which were used as Gospel Radio,I've help building many MW radio station in remote Area like  Wamena,Jayapura,Nabire  all in Papua/Irian jaya,also in Sulawesi ,Halmahera' .the problem is,we have not enought land and funds to build a full sized quarter wave antenna ,especialy enought land to place the ground radials./So the Efficiency of the antenna is poor.
So can anybody help me/give me information to build a compact / short profile antenna that's Efficient working in the Medium Wave band .I've heard about Isotron antenna,Gap antenna,EH antenna,CFA antenna,but can't find any detailed information about them,
So I'll be thank full if some one can help me designing/building such antennas


 Thanks

 Gito.N

I don't have personal experience with a MW antenna, but I have seen some commercial ham antennas that claim to do well on 160M, which is just above the AM band (what we call MW here?).

What frequency? that is important.

The first thing, is height. I know that much. The taller the better. If you do not have space for a 400FT tower, there might be some compromises that would work and would not be too expensive.

A friend put up a very large loop antenna for the 160M ham band using telephone poles (35FT?), and it is something like 150FT on each side. The wire even passes beside alot of trees/branches, and he gets good results on ham radio. I don't know if an antenna shape like that is suitable for broadcasting, can someone answer this?

Patrick

Yes I build several M.W transmitter  with 500 to 600 watt carrier output,and used in broadcast  Gospel radio in remote area and " underdeveloped" cities in Indonesia  like cities in Papua/Irian ,actually the  native people lived in the mountains and jungle ,so to reach them(by radio) we build this  Gospel radios,from my home town I have to travel by air (airplane) for 6 to seven hour to these places.
What bothers me is building an Efficient M.W antenna.
I help to build these B.C station(one of them) in Jayapura operating on 1170 khz,I managed to build a vertical antenna about 45 meter,and make 15 meter part off the Guy wire as the top load off the Antenna,I managed to bring the SWR to 1 /near to 1 by  taping the  matching coil at the bottom of the antenna For  the input power.
But I don't have Enough land/space to lay the ground radial.
And unfortunately  the Ground/resistance here is very high/poor,even for electric ground (50 hz) ,we have to dig and plant many ground rods,but can't get a good ground.
So because I don't have the tools to measure the R.F ground,by knowing the poor resistance for home ground,I'm sure there is a big resistance for RF ground, So the Efficiency of the Antenna must be low.
So there must be a waste to the power output and turn it into heat.

That' why when I read about the EH antenna, Isotron Antenna.Gap antenna,CFA antenna.(Short profile/efficient antenna without  Rf ground/ground plane as they claim)
I'm very interested
So can somebody/someone help me and give the Idea /help me to build such antennas


 Thanks

 Gito.n

Gito said:
Hi Gito and welcome to the AMforum. With regards to CFA/EH antennae, I looked into that quite a while ago. I'm still sitting on the fence wondering if it is indeed truly what they say or just a lot of hooey. I don't know anyone who built one for the 160M or any band for that matter so I can't really pass judgement. What I do know is that a lot hams have used a folded unipole very successfully in the 1.8 -2.0 Mhz region. Broadcasters have used them for years so if you are strapped for space, and money. I would go that route. A note on the Isotron, I don't think I would waste any money on that. I have seen them and they left me with a very bad impression. Remember, you get what you pay for.  I hope that helps.

I guess if you had lots of money a vertical dipole might be the way to go. It would be twice the height of a 1/4 wave vertical though.

 I used to think this was not very practical in the real world until I looked at the average height of some of the super cell phone towers lining all the interstate highways.   You'd think they would cover a whole state. Man, what they spend for 10 miles coverage....   :o

  Gito,

   I agree with Mike, and my vote would be the folded unipole, or folded umbrella. I built one of these once for 1.8 Mhz, and I was totally amazed. I once made it from Central Texas to New York with just 25 watts AM!

   I liked the fact that the antenna feed is higher impedance than a shortened vertical, and that the feed return was made to the tower, and not lossy earth. The downside is that you will need a tuning network at the antenna to transform the complex impedance to 50 ohms resistive (L-Network).

   The following link describes this in more detail:

http://lists.contesting.com/_topband/1997-05/msg00010.html

Best Wishes,
Jim
WD5JKO

To

Patrick,Mike.Rick ,Jim thank you for responding to me,and the Ideas you gave to me ,helps me,Now I'm trying to find articles about these folded unipole /folded umbrella  and hoping to find a detailed  construction to build these antennas.


Thanks

Gito.N

Gito, if you can afford it, try subscribing to antenna X. http://www.antennex.com/ (http://www.antennex.com/) Lot of discussion and good technical advice. I used to subscribe a long time ago when I was considering a different radiator. Do a google search and you can find tons of antenna forums with free information. Good luck and check back with us so we know what worked for you.

 
 Thanks Mike

  Gito.N

I am pretty sure the article I followed (Folded Umbrella Antenna) was in Ham Radio Magazine, issue May 1979 written by John Haerle, WB5IIR (SK). Maybe someone has a copy that they can scan and share. Here is another article written by John,

http://www.degendesigns.com/Downloads/TheEasyWay.PDF


Jim
WD5JKO

 Thanks again Jim I think I'll try to find out those articles .

Here' some pictures of the transmitter .one with me on that picture is a Transmitter using three 833 C as Rf final,and two 833C for the modulator,this Transmitter was used at Radio Swara Nusa Bahagia 1170 Khz in Jayapura Papua, Indonesia ,and the other  picture is the Transmitter using Three 813 as the RF final and four 813 as the modulator and used this transmitter in Radio Suara Lembah Baliem1062 Khz in Wamena Papua,which radio station ,which picture I have Attach before,The 813 was made 12 years ago and still running now .

Gito said:


Now they're my kind of transmitters!  ;D

Hello Gito,
Nice pics. You do nice work and you'll be rewarded later.
I agree with others here. Stay away from the "magic" antennas....GAP, Isotron, etc
I was wondering if others here would agree on erecting a 40 foot metal mast with a top hat and a tuning network on the bottom or "top loading" and top-hat (like the Cushcraft MA160V approx $300USD) and the usual ground radials, as long as you can lay them out. 60 minimum.
I know that ground conductivity plays a factor here and it might be better to use higher frequencies, but I realize that you're trying to make it easy to obtain a common radio for reception. The "grounding" of the radials is not for ground but for the return path for RF.
Gito is probably looking for something that's not going to be a maintenance nightmare that blows down in every storm.

Dick, the cell towers are designed for short coverage. About 5 mi max. They do not want anything beyond that. They are shooting for reliable communications in a small area for the .6watt cell phome and hand-off to the next cell.

Fred

From what I  have read on the topic, the CFA/EH antenna design is bogus.  These antennae have been tried out, and radiate almost exactly the same as a conventional short, loaded vertical of the same height.  The FCC has never authorised one for use in the US.

A more promising design might be the Kin Star antenna.  The FCC recently gave the go-ahead for the first onair KinStar antenna at KCST-AM Radio in Florence, Oregon. With 120 1/4λ radials, they claim 98% of the field strength of a full quarter wave vertical, at a fraction of the height.

It should be easy to build one.  There might be patent problems using a homebrew one for a commercial broadcast station in the USA, but I don't think they would have much jurisdiction in Indonesia.  Although they recommend a full size ground radial field for this antenna, it should work as well as any other type of vertical with less than ideal radial system.  It is basically a short top-loaded vertical with a "fat" vertical radiator consisting of a cage of wires.

http://www.kintronic.com/resources/brochures/40.pdf

http://nabshow2009.bdmetrics.com/PDT-364114/Kintronic-Labs-Inc-/KinStar-AM-Low-Profile-GREEN-Antenna.aspx

http://lists.contesting.com/_topband/2006-05/msg00061.html


http://www.star-h.com/products/reduced.html

Thank You Fred and Don for your response/information you gave me ,its 's a great inputs you gave me.
But the problem I have is not enough land to lay these RF Ground radials . So I am hoping to build an antenna thats Efficient enough without these radials.If its possible  .

When I am in Sangir North Sulawesi/Indonesia ,I found That The R.R.I(government  Radio ) used  this Antenna,According the Technician ,it's a good antenna .It's China made ,Is it a CFA?

Thanks

Gito.N

Wow Gito! That's impressive but it looks like a lot money spent on an antenna with extremely sturdy base. Now that might be built like that to resist the winds you might expect from the typhoons that occaisonally blow your way, (not to forget earthquakes). I've always been told to just get the radials down in the ground. Be it zig-zagged or take a mesh screen and bury as much as your property will allow. I'm not an antenna engineer but I don't think your radiation efficiency will suffer all that much if you get close to 1/4 wavelength. As a disclaimer, "Your mileage may vary!"

Like the Kin Star, I think the CFA and E-H antennas also require a full sized ground system.

The best thing to do, whatever the antenna, is to put down as many radials as you can, as long as you can make each one, in all possible directions.  If there isn't room for a full set of quarter-wave radials, use eighth-wave ones or less.  It won't hurt to make some longer than others. With a lesser ground system, you will lose some efficiency and field strength, but it's still better than what you would get by simply driving a metal rod into the ground.  Even at 20-30% efficiency, the antenna will still put out a respectable signal.  If possible, use more transmitting power to compensate for the compromise antenna.

But I would avoid the CFA and E-H designs.  The "amateur radio" short verticals that are widely advertised as "needing no radials" are bogus attempts to convince non-technically minded  hams to waste their money on something purported to defy the laws of physics.

Mike,
yes it's an expensive Antenna,it's the only one antenna used by R.R.I (Radio Republik Indonesia,a government  Radio),the technician there has no data sheet about these antenna,It' about 6 m (20 feet high ),These Antenna is placed in the middle of the Town (little town called Tahuna},and according the technician ,it works very well.The Transmitter they used is a 10 Kw Medium wave Transmitter made by Harris .

To Mike and Don,thanks for your Advise

here's a picture of the transmitter they used ,an the tuning box below The Antenna.

Thanks

Gito.N

n.b Sorry Mike ,I want to thank you but I miss wrote your name as Jim

Mikey LOOKIE,
The barrels (Green things) are the "fat" vertical part of that antenna!!! Wow what a design.
Might be worth experimenting with for 160M!!! Slightly scaled down. Get 10ea 50 gallon barrels and weld them together and guy with Dakron rope. Set these barrels on top of some treated lumber or railroad ties and attach a capacity hat. Top loading? Tuning network on the bottom??? Dunno! Someone should computer model that idea.

Gito, that might be the one to copy. But the rules are still the same for the ground radials. They don't have to be 120 feet long, just as many as you can.

Fred

Yep Fred, I knew they were part of the radiating element. I looked into the CFA a while ago but then all the hype about them dropped off the radar screen. I was subscribing to AntennaX at the time so they really put it under the microscope. At the time, I think there was only one array working and that was in Egypt.

The capacity hat in Gito's pics looks like its insulated from the rest of the antenna. That's the part I can't understand.
Is this the CFA configuration?

Antennas for MW and topband have always been fascinating to me

Fred

Yes Mike and Fred ,the 'capacity hat" is isolated from the rest of the antenna,to me it looks like a modified dipole with the other  half build like the "capacity hat",unfortunately I can 't get close to this antenna,because when I am
there,the transmitter is on air/transmitting.

Fred I, noticed they don't use any ground radial,considering the land they used is small.

this a picture of a MW broadcast Station I helped to build In Sangir .north Sulawesi indonesia.

Thanks

Gito.N

OK Gito
Then there is definitely a mystery in the design of that antenna. The real test is, how large is their coverage using this design and keeping in mind the transmitter power used. Apparently the Government can afford higher power transmitters.
Do you have access to aluminum tubing?
 How about this???? Two wooden utility poles about 50 feet high and then use the old freq formula for a resonant dipole antenna fed with every day coax? Or a shortened version with loading coils at the ends or just droop the ends down through pulleys at the poles to save some space. At those MW freq there's not a lot of choices for effecient antennas.
Good luck

Fred

Yes Fred ,

  it's a mystery ,maybe another kind of C.F.A based theory .Fred maybe an inverted V dipole is a better choice,but to tune it is more difficult I think ,or must I used an open wire line to feed this inverted V dipole, and using an antenna tuner to bring it to 50 Ohm impedance.
 An inverted V dipole has it radio patterns more closely to a vertical antenna than the patterns of a Horizontal antenna
Because in medium wave Antenna the ground wave is the much importance thing,that's  why we used vertical antenna.
Am I right Fred.

Thanks

Gito.N         

You are  right Gito,
The MW vertical tries to keep a low angle of radiation. Usually B'cast stations try to avoid skywave and keep their signal local.
The VEE and any other low dipole would create high angle waves that are good for 3-400 miles for Ham Freqs. I don't know how a VEE would perform at MW, but it seems like you have an idea of what to build. Your last post using a VEE and open ladder and a K1JJ tuner (nickname we gave for a nice effective balanced line tuner, built by Tom Vu, K1JJ) would be better than a vertical and insufficient ground radials.
Your MW freqs are going to be a problem for antenna design. You can't beat the law of physics.
Good luck
Fred
Fred

this is probably idiotic, but seeing as a helical wound antenna has been used here and there.. would it make any sense to wind a giant coil that happened to be resonant at the proper freequency?

Patrick

   When you mentioned Helically wound vertical antennas,I remberred  an article written about it in the ARRL antenna handbook(chapter 10) that says ...to achieve resonance in a shortened system .....the antenna can be helically  wound to provide a linear distribution of the required inductance, at the end of this article .it says .....Performance of this antenna is comparable  to that of many full-size quarter wave antenna.The mayor design trade-of is in usable bandwidth (narrow band with).

And it also stated  it can be worked against   an above ground radials.Some operators have good result using  with four helically wound radials which are cut for resonance or slightly lower than the operating frequency

A guideline might be to be maintain an element length of .05 wavelength or more.

It's not a idiotic idea at all ,it' a good Idea ,I've read this article before but theres no Idea using it ,before you mentioned it.

The only problem ,is technical problems,.....how to make/build this antenna technically  .

Thanks

Gito.N

I would be interested to know what frequency you broadcast on and where you got permission or the idea to use that frequency.

Swan

A little History about BC station in Indonesia.about 40 years ago there are many unlicensed small BC stations (Pirate Radio) here ,make the story short the Government then  make rules  " Peraturan Pemerintah Republik  Indonesia  nomor 55 tahun 1970  Tentang Radio Siaran Non Pemerintah (RSNP }( sorry ,in indonesian language)" Rules for non government Radio and we have an organization called PRSSNI,So to have permission to Transmit we must asked/permission to " menteri perhubungan" at that time(in Englih?) and must filled /gived them the documents and so...and so... to get A license for  BC radio.The  permission to used the Frequency is given by Government / Telecommunication minister ,We have 9 Khz channel here

One of the transmitters frequency is 1170 Khz with 600 watt RF output used in Jayapura  -Papua -Indonesia .

Thanks

Gito.N

Ps.Sorry  my English is not good

 
Thanks Gito you seem like a good man to me, hope to hear your station on soon.

I guess I will have to go away and eat my hat now........any one got any salt and pepper.

Swan

It's only a small MW BC  local radio,that has a limited range about 30 km to 60 km ,Maybe because the poor efficiency of the Antenna , I'm sure you can't hear my radio.
Sorry I can't translate some of my writing in Indonesian to English.Because my English is not good enough

Thanks Swan


Gito.N

Hallo! I'm an old SWL (but AML too). Searching for other things I dropped into this thread and I thought that a little, practical experience would be useful.
In Italy there has been only one case of broadcasting EH antenna, that of Radio 106 in Casagrande (a small place near Reggio Emilia). They transmit in AM on 1040 kHz and have no space for radials. Their antenna worked very well... for some hours, then simply burnt, because it could not sustain a continuous service as required for broadcasting.
The EH was placed on the top of an iron tower supporting other antennas (FM and GPS). After the third time that it was burn, they adopted another system, always with the aim of avoiding radials. This "thing" is made of a coax cable whose outer shield is connected to tower and the center wire to a tiny steel cable that rises oblique for about 53 metres to a pole on the side of the hill. No radials!
Obviously, calculations were of little aid in their case, and they lengthened and shortened the wire until they found the optimal ROS. This system has been in use two years and is still in use without inconveniences, and with a power of 300 W they reach a range of about 100 Km. I don't know if in the world one could find a smaller system for AM broadcasting!
Best regards to all and sincere wishes for Gito (and forgive my bad English, please!).

Hallo Fierabraccio,thank you for writing to me,may I asked you,Does the EH antenna work well before it burnt,what material did They used for the Antenna tubing.(Radio 106 at Casagrande)
I read an article /document(AM_Salvador) about a Medium wave Bc station.Radio Mi Gente.Am 700 in El Salvador that used an EH antenna,looking at the comparison data of 10 Bc station that has been normalized for power and Frequency that the EH antenna will be always will be the best performer for radiation and bandwidth (according this document).


You told me that the Co-Ax shield was connected at the tower,may I ask at the bottom,or somewhere at the tower ,and the tiny steel cable with was connected  to the center of the Co-ax rise oblique from...? is the Co-Ax at the bottom of the tower?(sorry  for my English)
 
Thank You Fierabraccio,best regards too


               Gito.N

Hi Gito! I didn't see the new antenna of Radio 106, I can tell you only that they told me. The hot end of the wire is placed higher than the top of the tower (about 25 metres high), but I don’t know how much higher. The cable shield is connected to tower at its top; but obviously the transmitter itself is connected to earth and in a certain sense the cable shield is connected (through earth) to the base of the tower. This is to say that nobody can know, in absence of further measurements, if only the wire radiates or if everything (wire, cable and tower) is actually radiating because of common-mode currents.
About EH antennas I cannot be of great aid. The principle itself of this antenna has been fiercely questioned. Here some of the major critical reviews:
http://www.w8ji.com/e-h_antenna.htm (http://www.w8ji.com/e-h_antenna.htm)
http://www.antennex.com/shack/Apr03/ontheeh.pdf. (http://www.antennex.com/shack/Apr03/ontheeh.pdf.)
http://www.antennex.com/preview/archive8/Nov205/intro1105.html (http://www.antennex.com/preview/archive8/Nov205/intro1105.html)
But criticism itself is questionable too. Many of their arguments depend by computer simulations, and computer programmes are based on a common state of knowledge that not considers recent developments as Vladimir Korobejnikov’s theories, on which Ted Hart declares to be based his antenna. Furthermore, some practical measurements were made, but on models (bi-cone or even half-cone) that were abandoned since the times of first CFA antennas.
(But CFA antennas seem to work, because the one you have seen and photographed in Sulawesi is undoubtedly a CFA antenna...).
Neither user’s opinions that one can read on the Web are of great aid. Somebody who tried EH antennas calls them “junk”, “snake oil” and worse; others declare themselves at the top of enthusiasm. But they all are amateurs, and there is a great difference between what an OM requires from his antenna and what is forced to require a broadcaster.
I don’t know why the EH antenna of Radio 106 did not sustain a continuous use. The firm that built it, Arno Elettronica, makes EH antennas for amateurs, perhaps they had not used materials suitable for an heavy-duty employment. But I suppose that they could have done some errors in calculating the feeding network: an antenna does not burn if it radiates correctly, when the RF current produces too much heat there is something wrong in its design.
If you are seriously interested, i may suggest to make some experiment by yourself. If you know somebody who has a FM station (and who obviously agrees to experiment), you can build and try “on the spot” a small antenna, and then decide if it is suitable for you or not. Here are two sites that can be of aid:
http://www.iw5edi.com/ham-radio/?eh-antenna-calculator,43 (http://www.iw5edi.com/ham-radio/?eh-antenna-calculator,43)
http://www.darc.de/f39/bastel/2003/wb5cxc/Tuning%20your%20EH%20Antenna.htm (http://www.darc.de/f39/bastel/2003/wb5cxc/Tuning%20your%20EH%20Antenna.htm)
http://www.yu1qrp.4sql.net/projects/files/EHArticles/EH_ANTENNA_DEFINITION.pdf (http://www.yu1qrp.4sql.net/projects/files/EHArticles/EH_ANTENNA_DEFINITION.pdf)
And that’s all. 73+88!
 

PS - I forgot another useful link, that of the site of Lloyd Butler (a renowned Australian OM who made some interesting developments on EH antennas):
http://users.tpg.com.au/users/ldbutler/index.htm (http://users.tpg.com.au/users/ldbutler/index.htm)

Gito
I was wondering if your organization would consider using FM instead of A.M.?
A 100 watts can go a long way and a better antenna to manage.
I'm assuming that the radios a lot of folks have today would be AM/FM capable.
Does your ministry provide the radios for the listeners? Or are they thinking that most people have A.M. only radios?
Shortwave would not be good for local coverage.
What type of coverage are you trying to get with the A.M. frequencies?
Fred

Hallo Fierabraccio,Maybe the Radio 106 used the tower as part of the ground system (RF ground) like a modified inverted V Dipole Antenna?with one half of the Dipole (tower) grounded at the end.(bottom of the tower).Actually there are many small Medium Wave Broadcast Station here,that's has lacked of land here,and they used Antennas like me (a short monopole/vertical /about 40 meter and don't use radials,only earth grounds).
Actually if the EH performed like They claim .it will be very useful here  ,in my home town there are  about six to eight Small Commercial M.W B.C station( with small budget/money and land).
Actually I also help to maintain A F.M radio here (as Technician) using 4 CX 5000.A factory build transmitter made in Itally.Yes it used a self supporting tower to place the F.M antenna),but to Experiment you must get permission of the government .
But thanks for your advices,it will help me.


Fred.there's a reason why we choose using Medium Wave AM transmitter.Fred I also help to maintain a F.M transmitter with 3500 watt 0utput and a M.W BC station with 600 watt output
The topography  here consist of hills/mountain and, valeys.
my town is surrounded by mountains ,to my experience ,using F.M there are many blank spot (because the Topography?,natural behavior /line of sight of FM transmission.) using Am (medium wave) we got more uniform transmission(coverage)
Also thinking why the Government still used MW transmitter ,there must be a reason.

Yes Fred before we build these station ,we has a research made,Especially the Topography of the site .
Yes The people there have radios for AM/FM.
We don't use shortwave transmitter.
The aim is to get many listener ,and of course as far as it can to reach the local listener (coverage),with it"s ground wave.


Thank you Fierabraccio and Fred


        Gito.N

Hi Gito! As I read, old AM can be still good....
About your antenna: if your problem is space, EH antennas are not the only way to resolve it. On the 136 kHz band, recently allowed to amateurs, many of them have been forced to contrive solutions to problems of electrically short antennas and lack of space for radials, and I believe that some of their solutions could be usefully scaled down to higher frequencies.
An example could be the ON7YD's capacitive antenna, of which I'm trying to attach an image (if I should not be able, follow the link below):
http://www.strobbe.eu/on7yd/136ant/ (http://www.strobbe.eu/on7yd/136ant/)
There you'll find technical details too.
Best regards & wishes!

Thank You Fierabraccio,it's a great input for me ,I will find this web.


Best regards and wishes too.


Thanks

Gito.N

Hi Gito,

Here are some folded unipole info that may be helpful:

http://www.nottltd.com/TheUsefulFoldedUnipole.pdf

http://www.nottltd.com/TheFoldedUnipole.pdf

http://www.kintronic.com/Systems/UnipoleSkirtKitGroundedTower.aspx

http://www.nottltd.com/ElevatedRadialSystem.pdf

http://www.lbagroup.com/technology/app10.php

If at all possible, try to obtain the book by Jeremy Raines who wrote a textbook on the topic.

As Don and others have pointed out, try to get as many radials as possible from the base at whatever length you can, and even elevate them if possible.

HI DMOD,Yes the articles you give will be abig help to me,Mike and Jim have told me about this Folded Unipole Antennas,but I can't find much articles about it,Thanks to You for these articles which I've been looking for.




Best Regarts

Gito.N

Vertical folded unipoles require a ground plane as conventional quarter-wave antennas. If I correctly understand Gito’s problem, it is of having not enough space for radials, whose effectiveness depends with their length as (or more than) their number. If Gito could have at his disposal enough terrain, this thread would have no sense.
Rebus sic stantibus, there are only two theoretical solutions:
a)   an earth-independent device, as a vertical dipole, that at AM broadcasting wavelengths poses a lot of problems;
b)   an artificial ground plane of reduced size but with the same effectiveness than an arrange of longer radials, but how one can realize it?
Both theoretical solutions could become practical with fractal antennas. As now, they are used mostly for UHF, EHF and so on (cellular telephony, GPS etcetera), but nothing forbids to use them for lower frequencies. I’m attaching some patterns of most common fractal designs, but there are many other possibilities.
Fractal design have been implemented not only for miniaturizing antennas, but also for miniaturizing ground planes. An arrangement of fractal trees all around a vertical radiator can take a small space and be effective as many longer radials.
 A friend of mine has recently made a receiving fractal antenna as a simple printed circuit on a vetronite board. For a transmitting antenna there would be some other problems, but I don’t believe they would be unresolvable. Here is a link to a site from which one can download many computer programmes for calculating any kind of antenna, fractal ones included:
http://www.si-list.net/swindex.html (http://www.si-list.net/swindex.html)
And that’s  all as far as I know!

Valentin Trainotti from Argentina has written some papers in the IEEE Transactions on Broadcasting (March and September of 1999) on the grounded dipole which seem to indicate that ground radials don't seem to matter much for this configuration.

A grounded halfwave antenna (lattice tower) is skirted with four to six wires. The outside of the coax is grounded to the tower near the feedpoint. At about a little over
0.25 Lamba, the skirt begins and at a little lower than that, a point is found for a match of 50 ohms. The center conductor of the coax is distributed out to the skirt. A platform is formed at this height inside the tower for supporting the coax and the skirt feed. No tuner is needed. In essence, the skirt is the matching transformer.

If the tower legs are grounded to some good ground rods, no further lightning protection is need.

I suspect the "Tunipole" mentioned in one of the references I gave you is a version of the Trainotti antenna.

I have the September IEEE paper if you need more detailed info.

Another consideration is to get a series-fed vertical as close to the population center as possible, with as tall a structure as possible (with capacitive or top loading if necessary) with as many radials as you can muster, and feed it with as much power as is legally or technically feasible.

Phil - AC0OB

Yes Phil,what Fierabraccio wrote about the antennas that I need was true a.   an earth-independent device.........b.   an artificial  ground plane.

But of course ,the more knowledge I got concerning many system to use  Vertical antennas ,would help me make more understanding  the + and -  of these antennas.

Phill,I'll be happy If You can give more detailed info about The Trainotti antenna.


Thanks Fierabraccio and Phill

Gito.N

Gito,

Please see your Private Message.

Phil - AC0OB

Thanks Phil.it must be useful to me.


Gito.N