eHam.net - Amateur Radio (Ham Radio) Community

Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net



[Articles Home]  [Add Article]  

H5ANX Mk4 Delta Loop Design

from Sajid Rahim on April 14, 2005
View comments about this article!

H5ANX Mk4 Delta Loop Design
By Sajid Rahim

Antenna Background

This antenna design was brought about by a need to have a simple effective and efficient antenna using simple materials. Its inspirations were derived from HCJB and W6SAI in his book “All About Cubical Quads”.

My experimentation started in late 1995 into quad loops as a means of achieving a 40m DX antenna that could be made at home and be put on 11m high mast. It had to be cheap and made from materials available in rural African areas. A dipole worked but did not have a low angle of radiation. Hence resulting research and experimentation created this antenna.

Discussion

The antenna is based on the basic principle of a full wavelength loop antenna. A single wavelength loop remains an efficient and effective antenna for all bands. It exhibits good gain (1.5 db over a dipole) and has various properties, which can be explored to make it better.

Its properties being:

1. A loop is most efficient when its circumference covers the largest surface area (delta, circular or quad shape).
2. Since a loop is a balanced antenna, it requires a balanced feed mechanism (more to be discussed later)
3. It has to be fed at a correct place to achieve respective polarisation.

It is these aspects when well understood will give this antenna its desirable characteristics.

i. Polarisation

A loop is vertically polarised when feed from the side. If fed from either the top or bottom, it is horizontally polarised.

Experiments have shown that the delta shaped configured loop works well when the antenna is vertically polarised. This means that one can use a simple support to hold the top of the antenna while spanning out the bottom edges using nylon string (Fig 3.)

This feed point, allows a low angle of radiation to be achieved at very low heights; an important characteristic for a DX antenna. A horizontally polarised antenna at same height will produce a very high angle of radiation. For lower frequencies, it becomes an important consideration.

ii. Feed mechanism

This is probably the most important question and which sets this antenna to be noted as different.

All reference materials available speak if using a 75ohm quarter wave coax. This was not available in my home QTH apart from television type. It is noted as not being efficient way to match.

Theoretical calculations showed the impedance of a delta loop cut at its fundamental frequency as being 150 ohms when fed from the side. A better option is a 4:1 balun (balanced to unbalanced transformer).

A choice fell on an air-core balun (fig 1.) as ferrite cores were not available and cost of obtaining a ferrite core is high.

This air-core balun is wound using following components:

a. 10cm long white/grey PVC pipe (black pipe contains carbon which absorbs RF)
· 40mm (1 ½”) diameter for 7Mhz – 50Mhz frequency range.
· 60mm (2”) diameter for 3Mhz – 30Mhz frequency range.
b. Simple zip cord (multi-stranded core insulated wire for lamps – two separate cores).
c. 8 turns of bifilar (18 gauge).
d. Loop is connected to terminals B and C.
e. 50 ohm coax is connected with RF (centre core) to C and ground wire (shield) to D.
f. A jumper is required from terminal D to A.

Notes: Wind the bifilar first, mark out the holes A,B,C,D to be drilled using a marker. Drill the holes and put in it stainless steel bolt and nuts (avoid galvanised/zinc plated which rust and create TVI).

When fed using a 50ohm coax, the balun transforms this impedence to 200 ohms which is close to matching 150 ohms. An effective swr of 1.33.

The loop also resonates on its second harmonic frequency with an impedance of 200 ohms. It, therefore, matches perfectly with 50 ohms feedline using the 4:1 balun on that second frequency range resulting in a 1:1 VSRW match; a flatline SWR becomes very visible. A extremely wide bandwidth being available across the usable frequencies.

iii. Length of the Loop and operating frequencies

The delta loop can be cut using standard formula of wavelength (m) = 286/Operating base frequency.

The H5ANX Mk4 loop will work on two fundamental frequencies of the loop. These are the base frequency and the second harmonic frequency ie. A 20m loop works for 20m and 10m, 80m loop works on 80m and 40m, 40m loop works on 40m and 20m without any tuner. However, the intermediate frequencies can be worked on without any problems using a tuner as the VSWR is below 3:1. These intermediate frequencies being 40m loop – 30m, 20m loop – 17m, 15m, 12m.

In the case of 40m loop; it will work on 30m and 20m but NOT on 15m/10m for transmitting purposes. It does match well BUT the feed point for these frequencies is now a high voltage point rather than a high current point. Consequently attempts to operate 40m loop on 15m and 10m will be met with the transmitter shutting down.

The length of the loop antenna should be preferable constructed with simple light insulated copper wire such as speaker wire.

Tuning notes: Please load the antenna using an AM carrier and measure SWR; the dimensions are above are always a bit longer; cut 10cm at a time and measure again.

iv. Orientation of antenna.

This antenna DOES NOT require height to give a DX performance. An 8 pattern is produced similar to a dipole.

Following configurations are given:

a. Inverted Delta Loop.

b. Delta Loop

This remains the most common way using the mast/support to hang the loop and expand out using thin nylon string.

c. Sloper Delta Loop

This configuration does produce small directivity to the direction in which the loop is slanting to as well as small front to back ratio.

Conclusion

Quad loop antennas remain as having excellent potential especially within amateur radio for their simplicity and their effectiveness. This antenna lays a foundation for further improvement by other amateur radio operators.

This antenna has served me well and the design has been replicated many times by other operators who report similar results. I am confident that this design will be of help to others.

Author’s background

I grew up in Africa’s heartland where television did not exist. Shortwave (hf) was the sole means of getting news of the world. My interest in hf grew as I started to develop an interest in antennas by which I could get better reception for my father’s shortwave receiver which was a simple 4 band shortwave radio from National.

At Rhodes University, situated in Grahamstown, Eastern Cape, South Africa, a group of us in 1991 laid the foundation for AstroSoc (Amateur Radio and Astronomy Society). The society amongst its early accomplishments put up a large astronomical observatory and amateur radio station. To date, this society continues to actively further its work and objectives amongst the students and community alike.

I obtained my advanced grade licence in 1994 with callsign of H5ANX (Bophuthatswana), ZS6EW, and A22EW.

My interests remain in Astronomy, Amateur radio, current affairs. Academic interests are in computer sciences specifically in formal compiler theory, cryptography, and operating system design. Work interests are in Financial Systems related designs and implementation.

Accredited with Bachelor of Science (Information Processing), Bachelor of Commerce (Honours) in Information Systems, and Master of Science in Information Systems.

For further information and feedback, I can be reached at zs735@yahoo.com.

References

a. All About Cubical Quads, by William Orr (W6SAI).
b. ARRL Antenna Handbook, ARRL

Member Comments:
This article has expired. No more comments may be added.
 
H5ANX Mk4 Delta Loop Design  
by NA4IT on April 14, 2005 Mail this to a friend!
Good article! Could you explain in a little more detail how to wind the balun...
 
H5ANX Mk4 Delta Loop Design  
by K3AN on April 14, 2005 Mail this to a friend!
"In the case of 40m loop; it will work on 30m and 20m but NOT on 15m/10m for transmitting purposes. It does match well BUT the feed point for these frequencies is now a high voltage point rather than a high current point."

I disagree. The feedpoint is at a current node for 40, 20, 15 and 10 Meters. If the feedpoint were a voltage node on 15 and 10, it wouldn't "match well" unless the balun was very inefficient.

I also think the overall loop wire length of 40.8 Meters (134 feet) is a bit short. I would suggest 43 Meters (141 feet).

I have built and used an 80 Meter sloping delta loop (upper corner feed). I have also built and used a 102 foot G5RV and a 130 foot end fed wire. Having used all three, I feel the loop is the best multi-band, simple wire antenna.
 
RE: H5ANX Mk4 Delta Loop Design  
by K0BG on April 14, 2005 Mail this to a friend!
Once again, this proves that necessity is the mother of invention.

Alan, KØBG
www.k0bg.com
 
H5ANX Mk4 Delta Loop Design  
by KB5GC on April 14, 2005 Mail this to a friend!
Questions: Would the inverted Delta loop be a "better" antenna because more of the radiator is away from the ground?

Does feeding the inverted Delta Loop at the bottom apex result in vertical or horizontal polarization?

Great stuff!

73,

Chuck
KB5GC
Holliston, Massachusetts
 
H5ANX Mk4 Delta Loop Design  
by WA1RNE on April 14, 2005 Mail this to a friend!

Sajid;

Nice job on the article, and a very good choice of topic. This is a very useful antenna for most HF bands.

I've had excellent results with Equilateral Delta's as well as rectangular loops for 80/75.

The last one I built was a 40 meter Equilateral fed at the center with a 4:1 balun, horizontal portion down.

My intent was to feed it 1/4 wave from the apex but it had to go up in a hurry before the first NE Blizzard this winter. This arrangement should provide better overall take-off angle, gain and impedance match.

As usual, Mr. Cebik, W4RNL is a valuable resource for antenna modeling data and analysis; his is the best I have seen yet:

http://www.cebik.com/scv/vdelt.html

73, Chris
 
H5ANX Mk4 Delta Loop Design  
by K4IA on April 14, 2005 Mail this to a friend!
Mr. Cebik is not too crazy about vertical deltas:

"However, whatever the configuration (apex up or down) and whatever the feedpoint (corner, apex, mid-horizontal, SCV, mid-side), it is unlikely to outperform even a simple center fed wire at the same height as the top of the delta."

Ouch.
 
RE: H5ANX Mk4 Delta Loop Design  
by N3EVL on April 14, 2005 Mail this to a friend!
"...However, whatever the configuration (apex up or down) and whatever the feedpoint (corner, apex, mid-horizontal, SCV, mid-side), it is unlikely to outperform even a simple center fed wire at the same height as the top of the delta...."

I thought the author's point was that it DID outperform such an antenna as you describe - did I miss something here?
 
RE: H5ANX Mk4 Delta Loop Design  
by K7JBQ on April 14, 2005 Mail this to a friend!
I think you guys are missing an important point: What Cebik is talking about is the effectiveness of a vertical delta loop, as compared to a dipole at the same height, as a MULTIBAND antenna:

"Although the vertical-plane delta loop either pointed up or down and fed virtually anywhere will radiate well enough to provide contacts, it is a relatively poor performer--in any configuration--when stretched to other bands, compared even to the simplest substitute."

The key words are "when stretched to other bands."

The tables in Cebik's article clearly indicate why this is so. The take-off angle in his example is pretty good on 40m, and quite good on 30m, but at 20m and up it's your basic cloud burner.

But as a single band, or in this case, dual band antenna, it will work well.

73,
Bill
 
H5ANX Mk4 Delta Loop Design  
by YN2EJG on April 14, 2005 Mail this to a friend!
You might try feeding it with a hand-wound balun made of RG-8X or RG-58mini on a toroid as EI7BA has done in this article.

http://www.iol.ie/~bravo/Cubical%20Quad.htm

I reconfigured my Gem Quad last year feeding each band with one of these baluns and it works well.

73

Ed
W5GCX
 
H5ANX Mk4 Delta Loop Design  
by KE7DFP on April 14, 2005 Mail this to a friend!
I've been eyeing one of these myself, but I think that except in a few very narrow parameters, it's a poor choice given space requirements. For a low band, your not going to get a low TO angle off a horizontal antenna without mounting at a lot of heighth. Compared to a dipole (40m) at 33 ft, it's a winner. Compared to a dipole at 66', it loses. So it's place is for those who don't have room for a dipole (1\2 40m). If you do have room for the dipole, you can hang 33 ft. plus off each end and have the Half Square. That's the winner.You will get 3 db gain and two verticals in phase (180 degrees), that don't need radials because they're top fed. The real beauty of the Half Square is, It works better with the ends low to ground. 5-15 ft. is fine.In fact, performance drops as you raise it up to 1/2 wave. That means that, if you can get that stinker dipole up just ten more feet (40-45 FT.) your in the optimized range. If not you can shorten legs and still do a lot better than the vertical Delta loop. The loop will probally be a better receiving antenna and is a good choice if you have under 50ft (length) to erect a wire. Oh, did I forget to mention the half Square feeds at 50 ohms from an upper corner. The current portions are at the top of your antenna where they do the most good. Mr.Cebik has much on his antenna site concerning this matter. I built one and was amazed. It served me well broadband also. It rules on 15 meters. I fed mine 1/4 run, 75 ohm coax, coiled into balun at feed point, the into 50 ohm coax. This made it tune perfect on 15m a little swr on 40m. I have very good ground and this design can double in low angle dbs over well conducting earth. The only problem was the ends have quite a strong field coming off them and my original installation ended one leg right above the bedroom TV. TVI forced me to move the end farther the other way. Randy KE7DFP
 
H5ANX Mk4 Delta Loop Design  
by ZS1AN on April 15, 2005 Mail this to a friend!
Reply to KB5GC:

1. An inverted delta fed at the apex at the bottom centre of the loop is horizontally polarised at its fundamental frequency (the frequency where the loop is 1 wavelength), as are all 1-wavelength loops that are fed in the centre and are symmetrical about the centre.

2. The horizontally polarised inverted delta has somewhat better low-angle performance than a horizontally polarised non-inverted delta at the same height, because the average height of the radiating sections of the wires is higher. Against that, it's harder to support.

73,
Andrew ZS1AN

email: my callsign at qsl.net
 
RE: H5ANX Mk4 Delta Loop Design  
by W6TH on April 16, 2005 Mail this to a friend!
.

A very good article and very interesting.

Have constructed many and found the gain at the fundament frequency to be a gain of 1.8 dB (1.5 dBi) compared to a dipole of 2.14 dB (1.64 dBi).

Remember also that the loop antenna become directional.

However the low angle of fire, with the loop, will be lower than that of a horizontal dipole at the same height above ground.

I still believe that a well designed vertical antenna will out perform the loop antenna, but you may differ.

Very well written post and have hopes for many more.

.:
 
RE: H5ANX Mk4 Delta Loop Design  
by A22EW on April 16, 2005 Mail this to a friend!
Chuck

I finally got to see the article after many years of not printing it due to other commitments. Do appreciate your support; it is much appreciated.

Questions: Would the inverted Delta loop be a "better" antenna because more of the radiator is away from the ground?

I found that the results were not that different. The issues for having two supporting structures for inverted delta negated the benefits.


Does feeding the inverted Delta Loop at the bottom apex result in vertical or horizontal polarization?

I believe you mean at the bottom of the inverted delta. It results in both a vertical and horizontal polarisation occuring. The vertical polarisation lobe is the most prominent one which has the low angle of radiation. The horizontal one has a high angle of radiation.

The big benefit is the dual bander nature. Especially if you have a 80/40 or 40/20 combination. It does work tremendously well on DX in these low bands.

Anyway, always appreciate fellow ham appreciation.
 
RE: H5ANX Mk4 Delta Loop Design  
by A22EW on April 16, 2005 Mail this to a friend!
The question on winding the balun.

Have a 2" length of appropriate diameter grey or white pvc pipe (avoid black due to high carbon content).

Drill two holes on the top - marked A, and B. Have the common speaker wire (red and blank coded - 2 part wire). Put in a stainless steel nut and bolt in A & B. Use Red component of the wire to start from A; Have black component of the wire to start from B.

Wind the wires into 8 turns. Pre-mark C and D holes once the winding is done to see where these holes will be most likely be. Drill holes in C and D and insert stainless steel nuts and bolts. Termination Red component which started in A into C; similarly black component from B into D.

Next is to setup the jumper wire. Cut a jumper wire which will terminate A into D.

Coax inner core will be hooked up to C; Earth/Shield component of Coax will hook into D. One leg of the antenna will connect into C; with the other leg into B.

Hope this will help.
 
H5ANX Mk4 Delta Loop Design  
by WK9L on April 17, 2005 Mail this to a friend!
Great article!
In my experience with loops, putting a 4:1 balun at the feed point in a loop you want to use for mutiband
is not a good idea. I have two vertical loops,one for 40 mtrs, and one for 30 mtrs. The 40 is fed though a 1/4 wave 75 ohm matching stub. This antenna out preforms any I have ever used but is not any good as a multiband. The 30 is fed with 300 ohm and works very well on 30 and also works well as a multi. And it will load on 40 but I am sure with a loss of gain. So in my opinion save the 4:1 till the shack and try an open wire feed. But the main thing is experiment and have fun.
WK9L
 
RE: H5ANX Mk4 Delta Loop Design  
by W6TH on April 17, 2005 Mail this to a friend!
.

The loop antennas are bi-directional and have a gain of 1.8 dB (1.5i).

The center fed Zepp working on the second harmonic, called two half waves in phase have a gain equal to the loop; 1.8 dB (1.5i).

Baluns or such are used on any Zepp and open wire line is most desired. A balun within the tuner is of good use for a balanced line and can be used with our present "T" match tuners.

I have used loops and found loops are not performing any better than the center fed Zepp; therefore I stay simple and have used the center fed Zepp for the past 60 years or more.

Now tell me where a loop will outperform a center fed Zepp. I will consider your theory as well.

.:
 
RE: H5ANX Mk4 Delta Loop Design  
by N6AJR on April 17, 2005 Mail this to a friend!
is it possible to feed 2 different sized loops with the same feed ( ala the fan dipole ) and get better coverage on different bands??

thanks tom N6AJR
 
RE: H5ANX Mk4 Delta Loop Design  
by W6TH on April 18, 2005 Mail this to a friend!
.

Tom, you know there is nothing better than the multiple dipoles (AKA Fan Dipole)in your estimation.

Why do so many change the name of antennas which have been around for so many years.

Why? why? why?

.:
 
RE: H5ANX Mk4 Delta Loop Design  
by W6TH on April 18, 2005 Mail this to a friend!
.
Hugo Gernsbach came out with the loop antenna back in the 30's ( 1930 ).

Hugo told me to take a length of wire and run it from bottom to the top and back to the bottom on my bedroom window, forming a loop.

Hugo also told me to load my ten meter oscillator to this loop, which I did. My first contact on 10 meters was a G3 from England. I was sold on the loop antenna at that time until I got word from John Kraus, W8JK to try his 8JK antenna. There, out went my loop and fell in love with the 8JK.

I then went into the military, WW2 and from then on it was "rhombus" Rhombic antennas. I left the military and from then on it was the Center Fed Zepp, also the design and theory from my teacher John Kraus.

.:
 
RE: H5ANX Mk4 Delta Loop Design  
by KE7DFP on April 18, 2005 Mail this to a friend!
A forty meter delta , apex up 57 feet, and base line at 20 ft. has a gain of 1.3 dbi at 19 degrees radiation. . (you'll lose that quick Feding your "broadband" balun operating off fundamentals.) This is for a loop fed 1/4 wave from apex, making it vertically polarized. This is a much more optimized scenario than our 35 foot at the apex, we're comparing to dipoles. The highest gain that can be achieved with this loop, horizontal up apex down, fed at bottom Apex is 6 dbi , but at a take off angle of 37 degrees. That's not low angle radiation. That also means your receiving noise at that strength from an angle you don't want to be receiving from. Now, take the same loop, cut half of the wire off, so you only have the top horizontal wire, with 7 ft. of wire hanging from each end, and you get 6.5 dbi measured at the maximum radiation angle of 33 degrees. Ok, 33 degrees isn't very low, but it's lower than it was before we cut half the wire off our loop!!, and we picked up 1/2 a db! Now if we measure the half loop we have left, at a 19 degrees radiation angle, we still have double the DBi at 19 degrees that the vertical delta loop had at 19 degrees. How good a design is that? If by getting rid of half of it, performance shoots up two and three fold. A good article covering the entire subject we have been discussing is "Notes on the all band use of Vertical Delta Loops" by Cebik on _www.Cebik.com_. Horizontal loops are a different story. So, if you only have a 35 ft. high support your better off with a flattop wire 1/2 wave wire . An inverted vee at that heighth, over an artificial ground plane, would also out perform the delta, I believe. (like your back yard chain link fence), or un attached base wire ) Once again we're cutting away the antenna to get better performance) and you'd get a better feed point resistance. That means eliminate balun loss. All band antenna? hardly, (a good duo bander). But w/ coax, baluns, high radiation resistances on some bands, no way. Not unless you're willing to feed it with open wire ladder line, 600 0hm feeder straight into a REAL antenna tuner for a completely balanced system. Then you will have exactly what you're after. But how many are willing to do that.? Running a T network through a 4 to 1 toroidal Dummy load, I mean, Balun, on the output. is not a substitute for a balnced line tuner. And that's all that is manufactured nowdays. It doesn't do what it's suppose to do, and toroidal baluns to step down impedances can't operate through the parameters and ranges required of them. You just think you're radiating all your power. Where do you get one of these real antenna tunners? I'm happy to say you have to build it yourself. You can't buy your way out of this one. And isn't that exactly the way it ought to be? Randy KE7DFP
 
RE: H5ANX Mk4 Delta Loop Design  
by W6TH on April 18, 2005 Mail this to a friend!
.
Randy, it is not very hard to build the coupler balanced match box.

On the 1.5 Kw MFJ 961, just rewire the caps to series tune the feeders and then link couple the center of the coil. Remove the taps from the coil and the switch. The coil can be split and add the link for coupling. Another capacitor across the coil helps for the parallel tuning.

Now we have series and parallel tuning. That is what I use on my open wire line to tune my Center Fed Zepp. Also ad the alligator clips for the proper matching inductance.

When I go to parallel tuning I close the two series caps and they short out at full mesh for the parallel tuning to take over.

73 W6th The Free Stater.

.:
 
RE: H5ANX Mk4 Delta Loop Design  
by KE7DFP on April 18, 2005 Mail this to a friend!
My point exactly, you couldn't use a manufactured unit through a 4:1 balun to get proper results , you had to build something to balanced feed your full wave dipole. Not quite sure what your circuit ends up being by description, my favorite is two roller inductors. One for each feed line, and one huge cap shunt across both. A 1:1 air core coax balun sits between xmtr and tunner (or) the original E.F. Johnson Matchbox circuit. But now we're getting off topic. 73s to ya Ke7dfp
 
Stupid Article!  
by GHOSTRIDERHF- on April 23, 2005 Mail this to a friend!
The trouble with you hams is that you spend too much time on this technical crap. Just go to the store and buy something off the shelf! You all make me sick!
 
RE: Stupid Article!  
by WB4TJH on April 24, 2005 Mail this to a friend!
Maybe "Ghostriderhf" should go get his GED and get back to his Clown Band radio and his 30db gain loaded mobile antenna and not worry about what real hams do.
 
RE: Stupid Article!  
by WB4TJH on April 24, 2005 Mail this to a friend!
Maybe "Ghostriderhf" should go get his GED and get back to his Clown Band radio and his 30db gain loaded mobile antenna and not worry about what real hams do.
 
Email Subscription
You are not subscribed to discussions on this article.

Subscribe!
My Subscriptions
Subscriptions Help

Related News & Articles
6 Band Wire Antenna
Get Rid Of That Lossy (Lousy) T-Match


Other Antennas Articles
6 Band Wire Antenna
Get Rid Of That Lossy (Lousy) T-Match