[wee-haggis]

I have 2 - 4221 clones and I am going to stack them outside on a rotor.

Both will be facing the same direction.

Just wondered if anyone has done this and if so,what the most successful method of stacking would be (ie

ne on top of the other or side by side....a-la 4228).

If one on top of the other ,what would the spacing be (some say to touch reflectors,some not).

If side by side,what is the spacing between the two.

Thanks

 

[mclapp]

Side by side (Horizontal Stacked) with the screens touching (bound together) will give you a narrow beam on UHF and some limited VHF-hi reception.


One on top of the other (Vertical Stacked) end up with the same beam as a single 4221 but with the vertical beam squeezed some. Space them so that the top v elements of 1 antenna and the bottom v elements of the other are spaced the same distance as the rest of the elements, I think around 8".


The UHF gain either way will be very close to the same, be sure to feed them with equil lengths of feed line and if using baluns they should be exactly the same too.


Keep track of the phasing, the right side of antenna 1 should hook to the right side of antenna 2 and left of antenna 1 to the left of antenna 2.

 

[Piggie]



Quote:
Originally Posted by mclapp /forum/post/15405217


Side by side (Horizontal Stacked) with the screens touching (bound together) will give you a narrow beam on UHF and some limited VHF-hi reception.


Keep track of the phasing, the right side of antenna 1 should hook to the right side of antenna 2 and left of antenna 1 to the left of antenna 2.

I think about as close as you can space two 4221As is about 20 inches center to center.


According to this chart The Two-Antenna Trick (outdoor version)
http://www.hdtvprimer.com/ANTENNAS/ganging.html


Here are my UHF channels


CH36 - 303 true WUFT

CH28 - 287 true WGFL

CH16 - 280 true WCJB


Ch31 - 249 true WOGX


CH29 - 221 true W29AB


Note on tvfool W29AB is listed wrong, it's on 29.0

I want to null Ch31 some, as it's overloading I think. All the first three come in full scale, so even though they appear borderline into overload they are fine. Ch31 though should be stronger but is only an 80 and I think considering it's closer and a lot more power, I think it's in overload. I have not tried it without the amp due to the location, but next time I am up on the roof I will. (Pigs have trouble on ladders).


It appears if I space them 20 inches (screens touching) but out of phase I should be close to what I need???????


All the channels are close together freq wise except 16, but it's pretty strong.


I tried stacking them on top of each other and things got worse. But I just have screen touching and according to your post they should be 8 inches or the distance of the other elements. I have them in phase. Every channel got worse than one antenna.


I did disconnect the 300 ohm wires on the bottom antenna and things got even worse. I tried to reverse them in case and I had them right.

 

[hphase]

In light of some comments that the new CM4228 doesn't perform as well as the old one, I thought I'd resurrect this thread. It has been suggested that perhaps you should just get two CM4221's instead of a new CM4228.


So, I'd like to try stacking two CM4221's vertically on the same mast. It makes sense to space the (now) eight dipoles pairs equally (8 inches) but what if you can't? Is it OK to "miss" a dipole and space the dipoles from the adjacent antenna by 16 inches?


Discuss!....

 

[neilkaz]



Quote:
Originally Posted by mclapp /forum/post/15405217


Side by side (Horizontal Stacked) with the screens touching (bound together) will give you a narrow beam on UHF and some limited VHF-hi reception.


One on top of the other (Vertical Stacked) end up with the same beam as a single 4221 but with the vertical beam squeezed some. Space them so that the top v elements of 1 antenna and the bottom v elements of the other are spaced the same distance as the rest of the elements, I think around 8".


The UHF gain either way will be very close to the same, be sure to feed them with equil lengths of feed line and if using baluns they should be exactly the same too.


Keep track of the phasing, the right side of antenna 1 should hook to the right side of antenna 2 and left of antenna 1 to the left of antenna 2.

In spite of having read much of what is online at various sites I need to ask what to use as a combiner. What are current options for commercially available and not terribly expensive combiners for arraying UHF antennas?


I have read that the venerable old 4228 (I still have two beat up ones here from about 15 years ago) is even better when each half is fed seperately and then combined via balun and combiner. I am hoping to do some experiments and mods.


Thx .. neilkaz ..

 

[hphase]

Anyone???


I've read a lot about stacking Yagis, but the 4221 ain't one of those...


Surely the CM4221 must interact with what is above and below it. Artistically, a proposed stacked array would look pretty with all of the bowtie bays aligned, but does that correspond to the best performance?


It almost goes without saying that the two will be combined with equal lengths of coax from the included baluns on each antenna. I don't see any need to get creative with anything else.


What do the models/experts predict?

 

[mclapp]

A regular 2 way splitter/combiner will work to combine the antennas. If you use a decent one the insertion loss will only be .5 db or so.


Vertical spacing the 2 CM4221 antennas further than 8" apart center to center of the very top and bottom elements should add some gain, but you are on your own on how effective it will be. Normally when horizontal stacking spacing the antennas further apart will give you a narrower beam with larger side lobes. I would imagine vertical stacking would work nearly the same but in the vertical plane (elevation)

 

[egnlsn]



Quote:
Originally Posted by mclapp /forum/post/16690187


A regular 2 way splitter/combiner will work to combine the antennas. If you use a decent one the insertion loss will only be .5 db or so.


Vertical spacing the 2 CM4221 antennas further than 8" apart center to center of the very top and bottom elements should add some gain, but you are on your own on how effective it will be. Normally when horizontal stacking spacing the antennas further apart will give you a narrower beam with larger side lobes. I would imagine vertical stacking would work nearly the same but in the vertical plane (elevation)

The insertion loss will be what the insertion loss of a 2-way splitter is -- 3.2-3.9dB, depending on frequency. While you will see that insertion loss of 3.5dB, you will also see an increase in the SNR by the same 3.5dB, which is always a good thing.


If you're stacking them vertical for one channel, the antennas should be 1/4 wavelength apart. If it's for a bandwidth, stack them 1/4 wavelength of the center frequency.


As has been written earlier, make sure the cables connecting the antennas to the combiner are exactly the same length. If not, the signals from each antenna will be out of phase with the other one, and pictures will be worse.