[logray]

Greetings!

I am a big big fan of the following website as an OTA resource as well as digitalhome.ca!

http://www.hdtvprimer.com/ANTENNAS/ganging.html

I enjoy DTV dx’ing as a hobby and regularly test out new antenna setups just for fun.

The most recent setup I’ve got is qty (4) Winegard PR-4400’s horizontally ganged together.

I’ve used the website above (hdtvprimer) as a how to for the balun design using twin lead, but I think I am missing something or the design is different for the PR-4400 than for the CM 4221. Reason being I’ve got some nulls and less db than with just a single 4400 - and it doesn’t make sense to me that I wouldn’t connect all of the inner lobes to one of the 300-to-75 ohm balun’s connectors – rather just to themselves and then to nothing???. Looking at the design below, the center lobes just connect to eachother (each side of the 4400 is electrically independent), but not the balun - so they are hanging there in free space? Am I not reading that correctly? If I am then perhaps my wiring is incorrect.

For a “two in series, two in parallel” connection on the winegard 4400, wouldn’t it look more like the following? That is, all of the center lobes connected to one side of the 75 ohm balun and all of the outer lobes connected to the other side of the 75 ohm balun?

Or, some other design?

Many thanks in advance,

-logray

 

[300ohm]

Reason being I’ve got some nulls and less db than with just a single 4400

Thats understandable when you horizontally stack. Read here under the two antenna trick:
http://www.hdtvprimer.com/ANTENNAS/ganging.html
As you can see, if the spacing isnt just right, youre bound to get some nulls.

I think youre better off vertically stacking or stacking in a 2 X 2 arrangement.

 

[jbkeh]

Am I not reading that correctly?

I believe the first diagram would be better described as "two in parallel (left side) in SERIES with two in parallel (right side)"; the second is simply "four in parallel".

The first has the left side paralleled to drop the impedance from 300 to 150 and the same for the right side. Connecting them in series raises it back to 300 ohms and the balun then drops it to 75.

The second simply drops the impedance to 75 ohms (and the balun then drops it to 18.75).

Note that the 4 antennae (elements) each directly feed a "centre point"; in contrast, many 4-element designs connect the "outer" element THROUGH the "inner" one (on each side). In this latter case, care needs be taken to ensure (as best as is possible) the signal from the "outer" element arrives "in phase" with the "inner" element so that their signals augment each other as they travel to the centre point. This is done by having the connecting line between the outer and inner elements being an even multiple of the (optimal) wavelength or an odd multiple of the half-wavelength with a half twist in the line to match up the polarity.

 

[logray]

Thanks for the replies!

In order to avoid the low impedance, on the all parallel configuration, I would have to ditch the 4:1 balun and go with a 1:1 balun - or just attach directly to the coax, correct?

With the 2 in parallel in series with 2 in parallel, I still think I'm missing something with the winegard PR-4400. Here is a diagram of how the elements are laid out on the 4400, does this look right if I were to follow Ken's diagram?

 

[jbkeh]

In order to avoid the low impedance, on the all parallel configuration, I would have to ditch the 4:1 balun and go with a 1:1 balun - or just attach directly to the coax, correct?

Yes. Purists would want the 1:1 balun, but many people using a Hentenna (a 75 ohm design) just connect directly.

Here is a diagram of how the elements are laid out on the 4400, does this look right if I were to follow Ken's diagram?

That's quite a mix of ideas!

The PR-4400 is a "balanced" 300 ohm antenna AT ITS CONNECTION POINT. Connecting at other points will play hob with the antenna's characteristics.

Erase the entire right side of the diagram.
Erase the connections to the remaining green balun point.
Erase the horizontal red line (leave the dots on the two antennae).
Move the two green connecting dots from the lower antenna element to the centre of each antenna's green wire (adjacent to the red dots).
Copy the left side to the right. Do NOT make a mirror image, just a straight move.
To the right of the green balun dot, create a red balun dot.
Between the two balun dots (and slightly above, to create a triangle) create a BLACK dot (or any colour other than green or red).
From EACH of the two green dots on the left side, run a green connection to the green balun point.
From EACH of the two red dots on the right side, run a red connection to the red balun point.
From EACH of the four remaining unconnected dots run a connection of the same colour to the BLACK (or whatever) dot.

The green/red pair for each antenna is the twinlead, which should be a multiple (including 1) of the optimal half-wavelength (which is the length of the wire from one element to the next). It should also be twisted (keep track of which side is which) and kept away from metal.

Also see the thread on stacking antennae; a horizontal array properly spaced must be quite a monster.

 

[logray]

The PR-4400 is a "balanced" 300 ohm antenna AT ITS CONNECTION POINT. Connecting at other points will play hob with the antenna's characteristics.

How did I do?

...twinlead...should be a multiple (including 1) of the optimal half-wavelength (which is the length of the wire from one element to the next). It should also be twisted (keep track of which side is which) and kept away from metal.

So for example, to optimize ATSC for UHF 25, I would want to go with twin lead of length 33.36" (including 1+1/2 wavelength) or a multiple, for example 66.72". Also does it matter how many twists per foot?

p.s. And yes, it is a beast!!!!

 

[300ohm]

How did I do?

If you go for a vertical stack, which I think is your safest effective bet, then connect up like on a 4 bay bowtie, ie, the two ends are crossed, the middles are connected up straight.

Also does it matter how many twists per foot?

The idea behind twisting the line is so that the line doesnt act like a radiating element. (with twin lead that can become a real problem) The old rule of thumb was 2 or 3 twists per foot for vhf, and 4 to 5 twists per foot for uhf (although you can do more, but you dont want to mangle up the twin lead too much).

 

[jbkeh]

How did I do?

Marvy. The only 'tweak' would be to change the colour of the black lines to match the colour of the corresponding antenna dots, to make the series portion more 'visible' (i.e. that the left side is in series with the right side).

For this approach, the wiring should be the same regardless of whether it is a horizontal, vertical or grid stacking.

(I must admit that there could be something I'm not understanding about the x-over design. To me, it is simply 4-in-parallel, with the outer elements 3/4 of a wavelength from the connection point and the two inner elements 1/4 wavelength from the connection point and the outer elements' phase reversed so the signal phase will match that of the inners. But that implies that the elements themselves are 1200 ohms and they appear to be simple dipoles.... Perhaps 300ohm can clear this up.)

So for example, to optimize ATSC for UHF 25, I would want to go with twin lead of length 33.36" (including 1+1/2 wavelength) or a multiple, for example 66.72".

Oops. In trying to be precise, I have been confusing. The length is strictly an integer multiple of the half-wavelength. I was just trying to say that the "multiple" could be simply "1". Personally, I'd just go with whatever half-wavelength the designers of the PR-4400 selected (distance between two adjacent elements times whatever multiple is required to permit connections, with ALL 4 twinleads having the same length).

Also does it matter how many twists per foot?

More twists are better, but it's diminishing returns; a couple will suffice. The purpose is to minimize the twinlead from acting as an element itself. Keeping it away from metal minimizes changes in its characteristics. (If the twinlead is of the 'shielded' variety, then this is not anywhere near as important.)

 

[mclapp]

Your best bet is to figure out what type of reception pattern you want. Stacking 4 horizontally will give you a verrry narrow azimuth beam and stacking them vertically will give you a verrrry narrow elevation beam. I know stacking just 2 vertically can be touchy elevation wise I couldn't imagine 4.

Your best bet would be a vertical and horizontal stack 2x2. People have had success vertically stacking pr8800's which would be the same idea.

Once you figure out the stacking arrangement then you will know your choices for feeding the antenna better. Keep in mind these are not resistors so which ever arrangement you use you can't just simply use parallel or series ohm calculations based on 300 ohms per antenna. The interactions of each antennas will change in the presence of the others in close proximity and will change with each channel.

Whatever you do you have to make sure that all the antennas are fed in phase all the right side feedpoints are hooked together and all the lefts to the lefts. Anything else will give you multi pattern beams and nulls.

Most likely they will be a better match with a 3:1 or 2:1 transformation overall.

 

[jbkeh]

Whatever you do you have to make sure that all the antennas are fed in phase - all the right side feedpoints are hooked together and all the lefts to the lefts.

The first part is true, but I would think the second is only valid in a parallel situation; in a series hookup, the 'right' feedpoint of one antenna would be connected to the 'left' of the next.

This configuration reminds me of the "Sweet Sixteen" fad (Popular Electronics) of several (many) decades ago when people were taking sixteen medium-sized speakers of the same model and mounting them in a 4x4 configuration, not only geometrically, but as four parallel strings of four speakers in series, all in phase. Net result was no change in impedance and the idea was that the speakers would 'smooth' out the minor differences among the cones and they would also act as a single surface with lower frequency and aggregate power-handling capabilities.

Call this a "Sweet Four"? (Two parallel antenna sets of two strung in series.)

 

[stampeder]

Wiring antennas in series is painful and/or useless in my experience and really messes up the impedence.

For this 4-way rig aligning each antenna to properly integrate into such an array can be difficult enough (best done on the ground and even with hardware store laser pointers aimed to a reflective target far away if you cannot do it with a carpenter's square to ensure a right angle of the reflectors). Aiming the array accurately once it has been aligned will still be very tricky.

 

[jbkeh]

There seems to be a blending of several diverse concepts.

Those who are 'concerned' about the circuitry of the 'two parallel sets of two in series' idea should take it up with Ken Nist - this thread was started to ask a question about THAT subject proposed on HIS page.

Those concerned with the merits of horizontal vs vertical vs grid stacking, element/antenna coupling and antenna aiming would be better referencing the Stacking, Ganging, Combining TV Antennas thread.

 

[mclapp]

The OP posted a picture of a wiring diagram from the HDTV primer site which has to do with ganging not stacking. If wired that way you will get a null as experienced and shown on the HDTV primer site.

I don't know if a total series hook-up would even work so I guess I didn't even consider it. The length of feeder between each antenna would have to be just right to keep the elements in phase from antenna to antenna even with that I'm not sure if it would work well.

In a 2x2 array the 2 side by side are usually connected in parallel and then those 2 are connected in series with the other 2 but even then all the left's are connected to left's and rights to rights.

You could do the same thing 4 horizontal or vertical by tying 2 together and then tie each set of 2 together in the center with a common line and hook the balun to the center of that. That would be sort of a parallel/series hook-up but even then all the right and left sides are tied together at a common spot.

 

[jbkeh]

If wired that way you will get a null as experienced and shown on the HDTV primer site.

Link please.

The length of feeder between each antenna would have to be just right to keep the elements in phase from antenna to antenna

Elements? Think that relates to element-to-element connections within the antenna. As for antenna to antenna connections, when would phasing NOT be have to be "just right" regardless of circuitry structure?

In a 2x2 array the 2 side by side are usually connected in parallel and then those 2 are connected in series with the other 2 but even then all the left's are connected to left's and rights to rights.

No, under Ken's alternative, the "lefts" and "rights" of each antenna in a paralleled pair are joined together and the combined "right" of whichever pair is designated as being "left" connects to the combined "left" of the other pair, with the remaining "left" combined and "right" combined connecting to the overall feedpoint. Whether the 4 antennae are horizontal, vertical or 2x2 is immaterial as is which two constitute one pair and which two the other as far as the circuit structure is concerned.

You could do the same thing 4 horizontal or vertical by tying 2 together and then tie each set of 2 together in the center with a common line and hook the balun to the center of that. That would be sort of a parallel/series hook-up but even then all the right and left sides are tied together at a common spot.

Diagram please.

 

[mclapp]

Link please.

No need for a link look at the proposed wiring diagram from the OP.

Elements? Think that relates to element-to-element connections within the antenna. As for antenna to antenna connections, when would phasing NOT be have to be "just right" regardless of circuitry structure?

Sorry for the mix up I think of the whole structure as an antenna and the pieces as elements so in my mind a whole antenna in an array could be an element or pieces of it, probably not the best choice of words. I think now we are just splitting hairs.

What I ment by "just right" is there is less tolerance than some feeding methods where it's not as critical.
Would you agree there are methods of attaching antennas and elements where phasing and feeder lengths are more critical than others?

No, under Ken's alternative, the "lefts" and "rights" of each antenna in a paralleled pair are joined together and the combined "right" of whichever pair is designated as being "left" connects to the combined "left" of the other pair, with the remaining "left" combined and "right" combined connecting to the overall feedpoint. Whether the 4 antennae are horizontal, vertical or 2x2 is immaterial as is which two constitute one pair and which two the other as far as the circuit structure is concerned.

You are correct that the alternative Nist shows is not connected that way and that is in my mind an exception to the common stacking methods most use. Probably due to the fact few use the type of line needed to stack that way.
I still haven't wrapped my mind around whether it would even work properly or not, for some reason I'm not picturing it, but I'm thinking he must of tried it or simulated it at some point.

Diagram please.

I don't have a diagram drawn up but on a 2x2 it would be where 2 are connected in parallel right to right and left to left then those are connected in the center by another line which puts the 2 previously stacked in parallel? with each other.

Although it wasn't shown I believe that's the way Nist hooked up his 16 bay example. It appears he used factory lines of the 4228's then connected a feed line between them. A diagram isn't really shown but the 16 bay pictures show the factory lines intact so I would think that's how he connected them.

What ever the case, however you connect them the point I was trying to make is that it's not a simple as add, subtract, multiply or divide of the single antenna(s) rated impedance to deturmine the common feed point impedance. The close proximity of the other antennas/elements even if they weren't electrically connected is going to affect the overall impedance. That is all

 

[PolyMeR]

mclapp,

I have two 4228's which are both missing the co phase harness. This is essentially a 2 over 2 stack. If I am understanding the diagram on post #6 then the top 4228 would have both lefts connected to one balun lead, the bottom 4228 would have both rights connected to the other balun lead then the remaing four leads would all be connected together. I wote an email to Ken Nist last year asking him about lossles stacking of two 4228's (16 bay). His reply was: "The optimum solution is four equal length 300-Ohm lines connected together at a single point. This would be perfectly lossless and of unrestricted bandwidth." When i asked him about the impedance balance he replied: "A twinlead “two in series, two in parallel” is not at all unbalanced if it is constructed properly."

I am not sure if this arrangement will work but I have the lines already made up. I never got around to testing this because I built an M8 and It works very nicely. Still, I am curious so i will test it out. Besides, I'd love a reason to build an M16

 

[jbkeh]

No need for a link look at the proposed wiring diagram from the OP.

I was looking for substantiation of your statement, "IF WIRED that way you will get a null as experienced and shown on the HDTV primer site." I believe the nulls/lobes are an artifact of the physical placement (relative to each other and the source) of the antennae in the array (and their phasing).

Would you agree there are methods of attaching antennas and elements where phasing and feeder lengths are more critical than others?

I'm far, Far, FAR too woefully ignorant on the subject to have an opinion. My 'gut' reaction is skepticism (but then, that was the common reaction to Ken's idea).

it would be where 2 are connected in parallel right to right and left to left then those are connected in the center by another line which puts the 2 previously stacked in parallel? with each other.

If you replace the word "parallel?" with "series" you have Ken's symbolic layout - as it is, that would be simply 4-in-parallel. Either way, the lines would not all be of equal length, although that can be compensated by having them in appropriate ratio.

From a mathematical perspective, one could take two antennae and connect them in series, repeat with the other pair and then join the two pairs in parallel. Same result.

the point I was trying to make is that it's not a simple as add, subtract, multiply or divide of the single antenna(s) rated impedance to deturmine the common feed point impedance. The close proximity of the other antennas/elements even if they weren't electrically connected is going to affect the overall impedance.

Could we settle for:

"Although it is relatively simple to calculate the THEORETICAL impedance of joined antennae of identical characteristics, if they are in too close proximity to each other and/or not all aimed directly at the source signal precisely and/or are not properly phased, REAL WORLD results will differ."

 

[jbkeh]

so i will test it out

Looking forward to that.

Although Ken never mentions anything beyond the 4 twinleads having equal length, my (oh so substantial, if not bright) 'gut' tells me they should be one or more half-wavelengths (adjusted for the velocity factor) of the desired centre frequency.

 

[PolyMeR]

Looking forward to that.

Although Ken never mentions anything beyond the 4 twinleads having equal length, my (oh so substantial, if not bright) 'gut' tells me they should be one or more half-wavelengths (adjusted for the velocity factor) of the desired centre frequency.

When I asked Ken Nist if the length of the four twin leads is important he replied:
"The length of the 4 lines is irrelevant, but all 4 delays must be identical."
So I made them identical to work with the two 4228's stacked with the reflectors touching per Ken's reccomendations.

 

[mclapp]

As Ken Nist stated the length isn't that important (as long as they are all the same) but the lengths of the lines could have some bearing for impedance matching purposes. Since the impedance of the antenna and the line will not be perfectly matched on all channels there will be some line reflections which could be used to actually make a better match on a range of channels and worse on others. Changing the lengths (all the same) could move the better and worse range around.

That would be extremely fine tuning which would be hard to do and get the desired results with the equipment most of us have available. It would be cut and try and most likely hard to notice. In any case with that set-up you would still have to make sure that all the feeders were the same length.

I'm thinking by Ken Nists responce on the alternitive method of connecting the 4 antennas that it may have limited bandwidth as compared to the parallel arrangement which was my gut feeling but that light bulb just hasn't turned on in my mind for exactly how the phasing stays in sync on the alternitive yet.