Four 3 Element Yagis on a single mast

[MrCoffee]

This idea may be far from actually working, but has anyone experimented with this idea?  (Seriously)

Think of the Folded Dipoles that are roughly a 1/4 wave separation between one another.  (From top to bottom)

Now instead of Folded Dipoles, install Four 3 element Yagis.  Either installed them with a 1/4 wave separation as the Folded Dipoles or make up a special mount so that they will

face North, South, East, and West but have them back to back so to speak.  Meaning they would be all in the same plane (level with one another) but facing the said direction.

I would like to think if 4 simple Dipoles can be tuned, why not 3 elements yogis instead of a single element.  Sure, phasing cables would have to be calculated as such.

The reason for only 3  elements per antenna, I am thinking the signal pattern may start to get tighter than one might want.

I wouldn't actually called them in phased either but I hope someone is getting the idea.  I would Just like to hear anyones thoughts on the idea.  Just a little back ground, I used to run Four 15 elements Yagis in what I call True Phase arrangement.  The frequency was between 144-148mhz.  I hardly ever used an amplifier.  One last thing I must add.  This idea isn't for a single station, but the idea of using this type of antenna for Repeater use.  All I ask here is to keep an open mind!!!

Thank you.

 

 

 

[BoxCar]

Look at cell towers. The antennas on each tier (candelabra) are in an equilateral triangle 120 degrees apart. The antenna elements are highly directional with excellent F/B ratios. 

For your plan, I'd look into building Moxon antennas. The physical size is quite small with about a 12 dBb gain and 30 dB front to back.

[gortex2]

The proper way to do this is with an antenna splitter on the tower. I've installed similar ones (corner reflectors) on a water tank. The problem is the splitter has more attenuation than one would like so ERP and RX suffers. Depending on feedline and other factors it can be overcome but not easily. 

 

[SteveShannon]

12 hours ago, MrCoffee said:

This idea may be far from actually working, but has anyone experimented with this idea?  (Seriously)

Think of the Folded Dipoles that are roughly a 1/4 wave separation between one another.  (From top to bottom)

Now instead of Folded Dipoles, install Four 3 element Yagis.  Either installed them with a 1/4 wave separation as the Folded Dipoles or make up a special mount so that they will

face North, South, East, and West but have them back to back so to speak.  Meaning they would be all in the same plane (level with one another) but facing the said direction.

I would like to think if 4 simple Dipoles can be tuned, why not 3 elements yogis instead of a single element.  Sure, phasing cables would have to be calculated as such.

The reason for only 3  elements per antenna, I am thinking the signal pattern may start to get tighter than one might want.

I wouldn't actually called them in phased either but I hope someone is getting the idea.  I would Just like to hear anyones thoughts on the idea.  Just a little back ground, I used to run Four 15 elements Yagis in what I call True Phase arrangement.  The frequency was between 144-148mhz.  I hardly ever used an amplifier.  One last thing I must add.  This idea isn't for a single station, but the idea of using this type of antenna for Repeater use.  All I ask here is to keep an open mind!!!

Thank you.

 

 

 

Simulate them using mmana or eznec. The amount of power delivered to the array is fixed so using a splitter will result in only 25% of the power being delivered to each antenna.  Without some kind of splitter you’ll have to figure out how to match the impedance an 18 ohm cluster of antennas to your radio.  The propagation pattern coming from four Yagi antennas will not be nearly as circular as from a phased array of folded dipoles; I think you’ll have four large lobes with areas of cancellation between.  But simulating them will tell you for sure. It’s an interesting idea, but if your goal is to create a circular pattern horizontally, start with an antenna that emits a circular pattern horizontally and use vertical phasing to increase the gain relative to the vertical axis.

[MrCoffee]

On 7/30/2024 at 9:19 PM, BoxCar said:

Look at cell towers. The antennas on each tier (candelabra) are in an equilateral triangle 120 degrees apart. The antenna elements are highly directional with excellent F/B ratios. 

For your plan, I'd look into building Moxon antennas. The physical size is quite small with about a 12 dBb gain and 30 dB front to back.

Hello,

I believe the antennas on a cell towers per face so to speak are connected per radio down in the radio cabinet.  Back in the day the cells ran three radios and then later 

added another cabinet with three more radios.  The tree antennas per face had one transmit antenna in the middle and two receive antennas on either side.

Perhaps I am misunderstanding what you are explaining, but I am paying attention, trying to anyway!

[MrCoffee]

On 7/31/2024 at 5:53 AM, gortex2 said:

The proper way to do this is with an antenna splitter on the tower. I've installed similar ones (corner reflectors) on a water tank. The problem is the splitter has more attenuation than one would like so ERP and RX suffers. Depending on feedline and other factors it can be overcome but not easily. 

 

Well the Folded Dipoles coax are all connected together, not using splitters, I'm just saying. (?)   However I would agree if using splitters or some sort of combiner 

would result in some attenuation.  I don't want to over think this, but I don't want to think this can work, when actually it cannot or perhaps wouldn't

be worth any possible gain when its all said and done.  Again as I had mentioned, I am paying attention what is being said.  I do appreciate any input as its

good food for thought!

[WRKC935]

Will it work?  Depends on your definition and application.

First issue is phasing and overlap.  If the splitter cables are not equal length then the overlap will have issues with not only the nulls from the beam width, but rf cancellation due to phase differences.

I would advise you to back up and look at the pattern of a single folded dipole and a yagi like you are talking about.  If you put four of them together at 90 degree angles from each other, you are going to see there are gaps.  Higher gain (more elements on the yagis will result in narrower beam width and bigger gaps.

 

I am not gonna say it will not work.  It can work and in some situations like being on a coast of next to an area with no population, it might even be a good solution.  But in those situations you are NOT wanting 360 degree coverage.

 

[MrCoffee]

21 hours ago, SteveShannon said:

Simulate them using mmana or eznec. The amount of power delivered to the array is fixed so using a splitter will result in only 25% of the power being delivered to each antenna.  Without some kind of splitter you’ll have to figure out how to match the impedance an 18 ohm cluster of antennas to your radio.  The propagation pattern coming from four Yagi antennas will not be nearly as circular as from a phased array of folded dipoles; I think you’ll have four large lobes with areas of cancellation between.  But simulating them will tell you for sure. It’s an interesting idea, but if your goal is to create a circular pattern horizontally, start with an antenna that emits a circular pattern horizontally and use vertical phasing to increase the gain relative to the vertical axis.

Eznec should surely show something.  Yes agreed, a splitter would attenuate.  And again as you mentioned with a fixed output doesn't help so to speak.

I understand the impedance matching between the antennas.  How come you mention 18 ohms?  Are you saying 18 ohms due to all four or 18 per antenna?  I was thinking

somewhere around 75 to 80 ohms per antenna by themselves.   As for the cancellation between the antennas, that would be quite true!  I never gave that a thought, and I am glad you brought that up.  I will have to rethink this idea and perhaps put it to rest.  Thats an important factor to consider.

[MrCoffee]

32 minutes ago, WRKC935 said:

Will it work?  Depends on your definition and application.

First issue is phasing and overlap.  If the splitter cables are not equal length then the overlap will have issues with not only the nulls from the beam width, but rf cancellation due to phase differences.

I would advise you to back up and look at the pattern of a single folded dipole and a yagi like you are talking about.  If you put four of them together at 90 degree angles from each other, you are going to see there are gaps.  Higher gain (more elements on the yagis will result in narrower beam width and bigger gaps.

 

I am not gonna say it will not work.  It can work and in some situations like being on a coast of next to an area with no population, it might even be a good solution.  But in those situations you are NOT wanting 360 degree coverage.

 

Hello,

I appreciate your comment, as I appreciate everyone who are chiming in.  After what Steve Shannon had brought up about the cancellation, this stopped me in my tracks to rethink  this idea.  One thought that comes to mind is the 8 and especailly the 16 Folded Dipoles that is on the market.  There has to be some over lap or cancellation involved with those antennas.  As mentioned, especially the 16 element Folded Dipoles.  Some more research is in order thats for sure.  

Perhaps I could shorting the Yagi down to only 2 elements and observe the results.  It will not erase or change what has already been said, but at least it will allow me to experience the results that perhaps lead in a positive direction.(?)  With that being said, I just had the thought of the second element only being mounted horizontal instead vertical.  One thing I have learned in this RF hobby, the higher in frequency, the more critical things get with interesting results.

 

[SteveShannon]

52 minutes ago, MrCoffee said:

I understand the impedance matching between the antennas.  How come you mention 18 ohms?  Are you saying 18 ohms due to all four or 18 per antenna?  I was thinking

A dipole, as used as the driven element in most Yagi antennas, presents an impedance of about 72 ohms. Four of them in parallel, without using some sort of impedance matching splitter, would be 1/4 of 72 or 18 ohms. 

[MrCoffee]

Oh okay I see how you came up with that now, since you spelled it out for me!  

Since the dipoles are in Parallel, you took the value of 72 and divided it by the four dipoles, I gotcha!

[WSBT754]

It can be done. With some effort of course.

https://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/qst/1996/02/page32/index.html

[MrCoffee]

Vey interesting on the Dimond stacked antennas.  I never heard that title or never heard from anyone ever experimenting with this idea.

I may have seen this set on a Cable TV company's Tower with four yagis antennas in this configuration, but I never gave it a second thought.

I find this set up very interesting indeed.  I am aware if stacked above one another this will result in a forward gain compared to side by side where the

gain is more left to right covering a broader distance instead of a forward distance.  Of course in a H Frames configration the gain is both broader to the right and left as well as in the forward direction.  

Thank you for the link.  I haven't looked at a Smith Chart or I should say a part of one in a while.

 

 

 

[WRYZ926]

Now if you are looking for an omnidirectional antenna setup, then look into square halo antennas. I mention square halls since they are easy to build at home and are omni directional. You can stack two halos vertically to increase gain.  You have to keep a certain amount of spacing between the two antennas and also make sure they are phased correctly.

I just thought I would throw out a different idea for antennas. M2 Inc sells what they call a 70cm loop antenna which is a square halo or folded dipole depending on how you look at it. They also talk a little about installing two together and phasing them. It would not be hard to tune one for GMRS use.

https://www.m2inc.com/FG70CMHOLOOP 

[BoxCar]

If you are building, you might want to look at a Moxon antenna as well. One tuned around 464 MHz is roughly 9 x 3.5 inches. There are calculators online that give all the measurements.