Can somebody to build medium wave antenna

[Gito]

 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

[Opcom]

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?

[Gito]

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

[W3SLK]

Gito said:

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

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.

[W3RSW]

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....   

[WD5JKO]

  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

[Gito]

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

[W3SLK]

Gito, if you can afford it, try subscribing to antenna X. 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.

[Gito]

 
 Thanks Mike

  Gito.N

[WD5JKO]

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

[Gito]

 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 .

[W3SLK]

Gito said:

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

Now they're my kind of transmitters! 

[flintstone mop]

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

[k4kyv]

Gito said:

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

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.

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

The antenna shown above operates at 1680 kHz and  is approximately 45 feet high and 105 feet in diameter and is over a full 120 quarterwave radial ground screen.  Details of the feedpoint at the center of the antenna is shown below.  The stainless steel box contains the transmitter and modulator used for testing.

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

[Gito]

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

[W3SLK]

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!"

[k4kyv]

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.

[Gito]

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

[flintstone mop]

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

[W3SLK]

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.

[flintstone mop]

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

[Gito]

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

[flintstone mop]

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

[Gito]

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         

[flintstone mop]

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