Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
questions about End-fed wire antennas




 
The AM Forum
October 16, 2019, 06:37:54 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: questions about End-fed wire antennas  (Read 1450 times)
0 Members and 1 Guest are viewing this topic.
AG5UM
Member

Offline Offline

Posts: 23


« on: March 21, 2019, 12:20:53 PM »

Does anyone know of books,tech-info sources,etc. for end-fed wire antennas?
all the ARRL books ,etc. cover 90% di-poles with antenna tuner all for 50 ohm,etc. same ol' stuff …
my MFJ 259 antenna analyzer is really of little use on anything over 50 ohms ,without adding matching transformers - circuits and just using it as a sig-Gen.
I have the old military grid dip oscillators and other things ,if I knew more about the subject.
 how to measure high-impeadance antennas, radiation patterns for end-fed wire antenna at various heights, gain,etc.etc...
currently, I have the MFJ -1982HP end-fed half-wave, it has mathing transformer, 50-ohm. so my antenna-analyzer works. I Have Heathkit DX-100 transmitter with no tuner and my analyzer says 1-1 on 7 MHz,etc,
However, I want to experiment with end-fed wire. How did they do this?
There must be books, info on this subject, but I haven't found much.
Logged
PA0NVD
Member

Offline Offline

Posts: 609


Nico and Chappie (Chappie is the dog...)


« Reply #1 on: March 21, 2019, 03:53:18 PM »

I used many half wave end fed verticals.  I am building one now for 40 meters.
My advice is to tune with an air coil and capacitor, The feed impedance is approx 3000 Ohms. The well known 1 : 9 transformers give in general quite a lot of losses. An inductor with coupling coil works really fine. You need approx 1 :8
Here  https://m0ukd.com/homebrew/baluns-and-ununs/end-fed-half-wave-antenna-tuned-coupler-efhw/  is a good article. The only thing is, I should put the coupling coil at the cold side of the coil due to the very high voltage at the top and use a coil with diam. / length ratio close to 1 to have a better Q.
I use to drive 1 kW without any problems.
Do use a counterpoise, I use a ground steak. No need for radials, but they do not hurt. Without a ground steak or ground, the coax can pick up noise. In general I do NOT connect the shield to the ground at he antenna for reasons of noise and statics during thunder storms.
I modeled an 1/2 wave vertical for 40 meters were at the lower half a non-connected half wave wire for 20 meters has been mounted at approx 2 inch distance. That does break up the antenna electrical for 20 meters only and gives you an array of two 1/2 wave verticals which have approx 6 dB over a normal half wave vertical and a radiation pattern almost constant from 18 - 50 degrees. It does not affect the performance at 40. You only have to switch the resonance circuit between 20 and 40 for two very nice DX verticals.
I have the results of the modeling, but I also did put them in the forum in "antennas"
Logged
KB2WIG
Contributing
Member
*
Offline Offline

Posts: 4317



« Reply #2 on: March 21, 2019, 05:31:38 PM »




Lots 'O stuff here.


http://www.tubebooks.org/technical_books_online.htm

look at
http://www.tubebooks.org/Books/orr_radio.pdf

and others.


Not enough stuff??

https://archive.org/stream/Cebik-Antennas#mode/2up

https://archive.org/details/w4rnlantenna

Enjoy.

klc
Logged

What? Me worry?
KK4YY
Member

Offline Offline

Posts: 392


Your best isn't as good as you can be.


« Reply #3 on: March 21, 2019, 08:13:12 PM »

To me, end-fed horizontal wire antennas are bit problematic. If it's the only antenna that will fit in your backyard, fine. But if you can fit a half-wave center-fed dipole or a full-wave loop in the yard, life will get easier for you.

In my opinion, you can make your own wire antenna that will perform better, and cost less, than the MFJ-1982HP. A good way to find out which is better, is to put up both the MFJ end-fed and a dipole or a loop and switch between the two. On-air reports will tell you what your antenna analyzer can't.

All I use is 14AWG Stranded THHN Black electrical wire from the local home improvement center - less than $50 for a 500' roll. I have about 260' of that about 30' in the air as a full-wave loop on 75M. I couldn't fit a dipole, it would be too long, 130'. But the loop, despite having twice as much wire in it, fits perfectly. It's a square 65' on each side.

So, go ahead and use the end-fed. Experiment and have fun with it. They're easy to put up, and they do work. For a lot of guys an end-fed was their first antenna — but not their last.

Pay close attention to the grounding requirements, as recommended in the MFJ product manual, for that end-fed antenna.


Don
Logged

Fate does not protect its worshipers any more than its deniers.
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7866


"Let's go sailing, Tommy!" - Yaz


« Reply #4 on: March 21, 2019, 09:37:51 PM »

Don said it very well...

There was a time when I had 18,000' of #5 aluminum copper clad wire. I went thru the whole roll experimenting using an antenna modeling program and 190' towers as supports. I tried every antenna known to man... :-)  Some were as big as 36 element 20M Sterba curtains, 7el 75M Yagis,  wire log periodics, vertical BC-style arrays for Eu - it goes on and on.

I found the only end fed antenna that worked well was an inverted L fed against ground for 160M / 75M DX, a receiving Beverage 6' off the ground.... and all the rest were prone to RF burns or inferior signals compared to balanced dipoles at the same height.

I can appreciate using an end fed if the backyard permits only an end fed. But if you want to save a lot of time, (like I went thru)  put up a flat, straight dipole as high as you can, (60-70' high is ideal for 75M) center fed with either open wire (and tuner)  or coax and be done with it. There is no better antenna. Symmetry is a good thang.  Antenna-wise, you will be par with the best stations on the air on 75M and 40M until you compete with Yagis, etc.

T
Logged

Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
AG5UM
Member

Offline Offline

Posts: 23


« Reply #5 on: March 22, 2019, 11:22:52 AM »

Thanks for the fantastic site!! www.tubebooks.org, its gonna take a while to look through, GREAT SITE!!
also, moukd.com is interesting.
Info. on broadside di-poles is everywhere,easy to find. K-mart probably sells a di-pole. slap on a tuner and use your 50 ohm analyzer..Boring…
High impeadance antennas,End-fed (horizontal wire),wire arrays,NVIA,long-wire antennas etc. etc. ,radiation patterns,gain ,measurements,directivity,etc. is not so easy to find information.
I have LOTS of room, I can literally,put up MILES of wire.
I only mentioned my End-fed MFJ-1982HP as an example,(which is 132 ft. horizontal wire),
It needs NO TUNER with the Heathkit, ( 1:1 with No tuner). it is MULTI-band(80,40,20...10 meters).
I am trying to find books and info. since I'd like to try some other things.
Again,thanks for the GREAT site.  Thanks.
Logged
AG5UM
Member

Offline Offline

Posts: 23


« Reply #6 on: March 22, 2019, 12:44:08 PM »

With a forest out here, I think I'll get one of those drones, fly about a half-mile of wire out and drop it across the tree tops,...
then I should be able to talk to my next door neighbor on the LONG-PATH,
whats the input impeadance for a half-mile of wire, 100 feet in the air?
 
Logged
Tom WA3KLR
Contributing
Member
*
Offline Offline

Posts: 1916



« Reply #7 on: March 22, 2019, 05:32:55 PM »

I have a 160 meter end-fed ½ wave antenna.  I’m very happy with it, wished I had put it up many years before I did.  One reason I chose the end-fed is that my house is in the middle of 10 acres of cleared land.  The feed end of the antenna starts at a 30 foot mast outside of my pole barn about 35 yards behind the house and the wire runs to a tall tree at the rear corner of the property.  The far end of the wire meets an insulator about 2/3 of the way to the tree.
 
I get very good signal reports; I run only barefoot sideband and a Johnson Viking II on AM.  I was always amazed at the signal from Mike N8ECR in Michigan who ran an end-fed antenna on 75 meters for the DX-60 and Multi-Elmac nets.

I run a 50 Ohm coax out to my pole barn under the grass from the house.  In the pole barn is my home-brew antenna tuner built in a Hoffman enclosure with a parallel resonant tank circuit with a large coil and a large air-variable capacitor.  I had read that the impedance of end-feds were around 4000 Ohms as I recall.  When I finished building the tuner, I put a 3900 Ohm resistor on the output and tuned it at the bench with my MFJ-259.  The tap from the coax center is about 3 turns from the bottom/cold end of the inductor, and then also driven with my HP606B signal generator.   The antenna connects to the top/hot end of the coil. After it was tuned and matched with the 3900 Ohm resistor, I measured the r.f voltage from the resistor and was able to calculate the loss.  As I recall it was about 0.7 dB.  After the tuner was installed inside the barn, the tuner was found to be close to matched.

The operating bandwidth is very narrow.  I can only operate +/- 4 khz.  To change frequency, I make a trip out to the pole barn with my MFJ-259 and plug it in to the SO239 in place of the coax, re-tune to the new operating frequency.  A motor could be added to the air-variable shaft if quick remote frequency agility is needed. But this is not needed in my case.

The tuner box in the pole barn is mounted at eye level.  I have two wires coming off of a stud on the bottom of the box to two ground rods.  There is a ceramic standoff on the top of the box and a # 12 or 14 stranded wire passes through a hole in the wall of the barn and this single wire is the vertical lead to the insulator at the start of the horizontal portion of the antenna.  I drilled a 2“ diameter hole in the wall of the barn with a 2” circular saw bit.  I cut a square piece of Plexiglas and drilled a hole in the middle just a hair larger than the o.d. of the insulated down-lead.   The lead passes through here adjacent to the top of the ceramic stand-off.  There is a SO-239 connector on the side wall of the box with a clip lead in the box to the tap on the inductor.  The coax to the house happens to run almost in line with the antenna, in the opposite direction going to the house.  So, the coax may act as a counter-poise to some extent for the system.  I have no noise problem.

To me, it seemed unattractive and unnecessary to use a piece of ladder line from the tuner to the horizontal section of the antenna. Some people have said “oh you have an inverted L with some vertical radiation” Well so what?  Since I knew my mast won’t be tall (only 30 feet) the vertical portion isn’t much of a percentage of the antenna.  Since the feed point is a high impedance the current is low and there is very little radiation here anyway.  One nice thing about the end-fed half wave is that where the high current node is, there is nothing there except the bare wire; no down-lead. This may be a help. Surely, the radiation pattern in practice is a little different than a center-fed half-wave dipole, but neither is perfectly symmetrical.

The worst signals I have run into on 160 are people who are running a ¼ wave inverted L with little ground system.  That system needs an extensive ground radial system to work well.

So this is my 2 cents worth, good luck.
Logged

73 de Tom WA3KLR  AMI # 77   Amplitude Modulation - a force Now and for the Future!
PA0NVD
Member

Offline Offline

Posts: 609


Nico and Chappie (Chappie is the dog...)


« Reply #8 on: March 22, 2019, 05:47:58 PM »

Your experiences match mine quite closely Tom. I had them for 20, 40 and 80 like that and for 14 and 18 MHz I had vertical half wave  end fed antennas.
I did broaden the bandwidth quite a bit by coupling with a resonance circuit, not with a tap or coupling coil. You can calculate the Q of the antenna tuning circuit by dividing the 3500 Ohms with the impedance of the coil or cap. Than make a series resonance circuit at the coax with the same Q, dividing the coil or capacitor impedance with 50 Ohms. Couple the two circuits with K x Q = 1 or just a little more. You get a BW curve like a band filter which is wider than just one resonance circuit and with a flat top.
An additional advantage is that there is no physical contact anymore and a nice distance between the coils so much safer in case of thunderstorms.
Logged
KK4YY
Member

Offline Offline

Posts: 392


Your best isn't as good as you can be.


« Reply #9 on: March 22, 2019, 09:25:16 PM »

Here's a book that I just found online. I have a hard copy of a previous edition — it's about 3 inches thick. Break out your slide rule, here's comes the Antenna Engineering Handbook!

http://seklad69associates.com/seklad69associates.com/EEG_808_and_815_files/Antenna%20Engineering%20Handbook.pdf
Logged

Fate does not protect its worshipers any more than its deniers.
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7866


"Let's go sailing, Tommy!" - Yaz


« Reply #10 on: March 22, 2019, 10:04:43 PM »

Good comments all around...

A few more about wire antennas:

A horizontal 1/2 wave piece of wire will exhibit the same bi-directional "dipole" pattern whether it is fed directly at the end or fed balanced in the middle...period.   What changes the vertical and horizontal pattern with an end-fed is the lead-in to the ground or shack - thus lengthening the total run and creating a different lobe structure - for better or usually for worse. (and requiring Earth ground to work against since there is no transmission line cancelling)

A VERY long single wire (> 5 wavelengths) will begin to get very directional to the point of having to pick the two cities you wish to talk with (NE/SW)   Wink ... and being rather pissweak elsewhere due to the big nulls in the pattern. This is why a standard 1/2 wave dipole works so well for general bi-directional "dipole" coverage.

For the most acreage-efficient very large wire array, (end-fed) a rhombic antenna of several wavelengths is the best antenna. A terminating resistor can make it uni-directional. (one direction with front to back)  One-half wavelength high is the minimum height to see a rhombic really play.

The longer the wire antenna, the higher it needs to be in the air to compensate for ground coupling. IE, on 75M a standard 1/2 wave dipole at 120' high has a beautiful low angle lobe for DX.  Make the antenna  a full wave long and it needs to be at 140' to accomplish the same vertical take off angle. (approx)    This relationship also applies to a full-wave horizontal wire quad.  This does not apply to "traveling wave" antennas like an end fed Beverage receiving antenna which uses ground as the other side of a transmission line - and works best 6-8' off the ground - still producing a low vertical takeoff angle...

End fed wire antenna's biggest problem is the lead-in wire that can pick up RX house noise, create RFI in external devices, etc.  A better idea is to run the matching device under the antenna outside or better yet mount it remote controlled on the tower at the same antenna height as the end-fed wire. A coax feed from shack to the tuner will keep RFI at bay.

To really create some extraordinary gain with a balanced wire array, a pair of Lazy H's  side by side fed in-phase with reflectors is about the biggest bang for the buck. This is a SIXTEEN element wire array. The bottom elements need to be at least 3/8 waves above the ground to perform well.  It can be fed with open wire and tuned to several bands, though the reflectors will only work on one band.  Four driven bays of Lazy H's phased and fed with open wire can be made to work with f-b too.  I have run this antenna on 20M for Europe, but twice the size as described.

Height above ground will have the biggest effect on any HF antenna, end fed included.  Low height will retard gain and directivity.  An antenna  1/2 wavelength above ground is considered a good standard. As the frequency increases (40M and above) 1-2 wavelengths above ground are needed to match the most optimum angles for DX. Stacking antennas becomes the next door to open.

To a limited extent, the higher the antenna, the sharper the horizontal beam and the better the front-back. This is especially pronounced on 75M where 1/2 wave is 120' high and any less causes the antenna to be greatly influenced by ground losses and coupling.



UPDATE:  (Some more info on low vs: higher antennas)

After extensive A/B on-air testing, for local work on 75M from 30 miles to 600 miles away, I've found a dipole at about 60-70' high to be optimum. A low dipole, like at 30' high, exhibits ground losses and high angles that appear to be too high (NVIS style) for ham use. A take off angle of about 60 degrees or lower appears to be a good compromise most of the solar cycle and time of day. Thus a dipole at 60-70' high fits the bill.  I posted a thread on this BB about this test.

http://amfone.net/Amforum/index.php?topic=34044.0

More about practical gain antennas:
http://amfone.net/ECSound/K1JJ21.htm

T
Logged

Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
AG5UM
Member

Offline Offline

Posts: 23


« Reply #11 on: March 23, 2019, 12:49:31 PM »

I appreciate your taking the time to describe your antenna and installation, low noise on 160 would be great.I should try building one sometime.
I do have a sliderule, thanks for the antenna book site.
very interesting comments on wire arrays,etc. I hope to get there eventually, very cool. also, about antenna height,etc. good info. Thanks.
I have a small utility trailer which I mounted a pole on, (too low at present, I need to build a taller pole/tower for it), I can move the end of the wire any direction, My idea was to find the best directions before putting up my poles/towers. however, from your comments, the directivity will be very different with antenna height.   Thanks for all the info., ideas,help.
I'll be reading your comments and looking through the book sites for a while, a lot of great info. Thanks,to all!!     73,

Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone © 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.063 seconds with 19 queries.