But even in a best case scenario of combining two CM4221HDs, you have the .5 db min loss from each of the built in baluns
Even a single antenna usually has a balun, with the same loss. But only one of them. A second balun adds only 0.5dB loss (or whatever), not 1dB. And this still does not change the math that gives +2.5dB or so from combining two identical antennas with or without baluns.

In practice (rather than armchair theory), the two combined PR8800s work spectacularly well here, whereas a single PR8800 does not have nearly the reach.

This indicates a real-life gain of probably 2dB or more.

But I do still plan to go for that extra 1dB or more, by getting rid of *both* store-bought baluns, in favour of a direct wire connection between the two antennas, with a single coax-loop balun in the middle.

Cheers

But mclapp, doesnt your 8 bay work much better with the phasing lines than it would have if you had used two baluns and a splitter to combine the 4 bays ?

I tested it last fall both ways using a spectrum analyzer the main difference was where the peak occured, the open wire feeder peaked around 580mhz and the 2 balun set up peaked a little higher (610mhz).

There were spots where the open wire feeder was 1 db better than the 2 balun and places where the 2 balun was .5db better and other spots where they were even. In both cases the the 8 bays were 1 -3db better than the 4 bay except above 700mhz.

The average gain across the ch 14-50 range my have been .5 db better for the open feeder. I was using a pair of phillips $1 baluns and it's been noted that balun quality can make a difference as well.

These were the results from my particular test someone using different lengths of coax, baluns, or a different type or length of open feed line will get something different for sure.
http://www.frontiernet.net/~mclapp/Antennas/plots/8%20bay%20feeder%20test.gif

But only one of them. A second balun adds only 0.5dB loss (or whatever), not 1dB.
Thats what Im saying, .5 db loss from each balun, giving 1 db total. But Im also using the often quoted .5 db insertion loss per connection, which is probably too high. Someone needs to do a loss analysis of the splitter using it as a combiner, because that loss cant be zero either.

Yeah, Im conducting my own real life testing today. It seems to me that snow is better for reception than rain, heh.

http://img518.imageshack.us/img518/6138/snow030209.jpg

Great photo!

We get tons of that white stuff here, too, but it never builds up on the antennas, thank goodness.

Cheers

Is it possible to simply use aluminum wire to connect the elements of two antennas? Where would you do it? Eg on two 4221s- whiskers or reflector? Is this better than using a conventional joiner/reverse splitter for signal gain/loss?

I know this might be more about the new 4221HD model, but several years ago, I wanted to put a 4228 in my attic on a rotor (didn't really want anything outside if I could avoid it). But the opening to my attic was small and would only allow a 4221 to fit through. So I bought two 4221s (the old kind, of course) and attached them together side-by-side with two long horizontal metal brackets attachd to the backs of the reflectors. I then mounted them on a mast (the mast and brackets clamped to the back side of the reflectors right at the vertical seam between the two), with the U-bolt clamps holding the edges of the reflector screens together right at their edges and against the mast.

I then followed some online close-up photos of the 4228's connection setup, and I fashioned stiff parallel aluminum wires to connect the two 4221s, joined at the center in front of the antennas just like the 4228. I used a small rectangular piece of wood and drilled two holes in it for the attachment bolts. At the time, I tried to orient and wrap the aluminum wires to look identical to the 4228 picture I was following. I used whatever 300-75 ohm balun I had sitting around at the connection bolts and ran coax down to the tv from there.

This setup has worked well over the years. Analog signals were receivable out to about 60-65 miles with a signal strength of about 7 out of 10 (maybe 8 out of 10 at night). In digital, it is right on the threshold of 65-mile reception (somewhat stable at night, not stable or nonexistent during the day).

This question is quite timely for me now, as I've learned a lot about antennas by lurking on this board for a while. From reading the recent balun thread comments, I plan to replace the existing balun with a CM 0089/94444 that I just bought, to see if that helps any. Also, (now that I know much more than when I connected these 4221s) I now suspect that perhaps the lengths of the two aluminum wire connector pieces are supposed to be exactly identical. Could someone please confirm that for me? They might be identical (or close), but I'm not sure how exact I was, so I plan to check that soon also. Although the aluminum wires I fashioned are parallel, I knew nothing at the time about their wrapping at, or angling away from, the attachment points, nor did I know anything about distance for these wires in front of the antenna or proper spacing for the attachment bolts at the center wood block. I'd very much appreciate any comments on which of these might be critical dimensions, and I'll adjust/improve accordingly.

I also seem to remember reading some recent comments about wood pieces/blocks not being that great at connection points for SBGH/DBGH antennas (PVC or other plastic was recommended instead). Wondering if I should replace that wood piece connecting my 4221s with some PVC/plastic.

As a side note, inspired by DogT, 300ohm and others, I've nearly completed a 30"x75" DBGH (original screen version) that very closely resembles DogT's PVC design. I plan to compare the results to my twin 4221 setup, and I'll of course report my results here.

Thanks to all for this very informative and helpful forum...

I now suspect that perhaps the lengths of the two aluminum wire connector pieces are supposed to be exactly identical. Could someone please confirm that for me?
Yes, the phasing lines should be exactly identical. I noted a difference on my first DBGH when they were just 9mm different, reception was better when I replaced them with one that were exactly equal +/- .25mm.

but it never builds up on the antennas, thank goodness.

Yeah, this one was real sticky and heavy. Broke a lot of branches and power lines.

because that loss cant be zero either.
When used as a splitter, the good listed ones have a 3.5db loss. Since the splitting of the signal is 3db, that would mean at least a .5db intrinsic loss in the device. The unmarked ones, from what Ive read, are 4.5db loss or greater when used as a splitter.


Perhaps these old Channel Master 300 ohm twin set couplers would be lower loss, note the different model numbers on the flip side of the bakelite, heh :
http://img129.imageshack.us/img129/3021/dscn0506648x486486x364.jpg

http://img255.imageshack.us/img255/7510/dscn0508648x486486x364.jpg

I'm interested in this thread as well.
As I said in an earlier thread, I've tried to stack 2 of the (old model) CM4228 8 bay bowies.
I tried 2 methods:
(a) using a separate balun on each antenna then combining the outputs using a splitter.
This gave the better results, although not that much better than a single antenna by itself.
For stations about 60miles away, there was a noticeable improvement over a single antenna.
For stations about 120miles away (detroit) it seems to be a little worse than a single antenna (presumable because the splitter and extra cable are killing the signal. With a single antenna, I run a cable from the balun to the TV. With the stacked antenna, I run a 2ft cable from each balun to the splitter, then the original cable from the splitter to the TV, so there's an extra 2 feet of cable with a connector on each end and the splitter)

(b) connecting the antennas with 300 Ohm wire and using a single balun.
I used Nexxtech 1501174 which is "300 Ohm super low-loss foam twin lead 20 ga. copper conductors with polyethelene foam insulation and wather sealed jacket" from Source by Circuit City.
The results were bad: not even as good as a single antenna.

Someone suggested the issue for (b) may be the impedance: is there a source for 2:1 (or maybe even 1:1) baluns for TV ?

when you were connecting with twinleads, did you try to reverse the polarity of one of the two connections when you found out that the results were bad?

often, by reversing the polarity, the antenna work together in-phase instead of opposite phasing from each other

when you were connecting with twinleads, did you try to reverse the polarity of one of the two connections when you found out that the results were bad?

often, by reversing the polarity, the antenna work together in-phase instead of opposite phasing from each other
yes, I tried reversing the twinlead at one antenna.
The impedance theory seems to make the most sense

I've used 450 ohm twin lead to connect the 2 halves of my homemade 8 bay and it worked quite well overall. If you look real close at the picture you can see the windowed 450 twin lead.

http://www.frontiernet.net/~mclapp/Antennas/8%20bay/8%20bay%20bow%20front%202.jpg

I did find certain channels where it didn't make much difference in signal over a single 4 bay. Changing the length of the feeders will change where the gain dip or peaks are.

I would think that 300 ohm twin lead should be similar. Those antennas only have a small area where they are truely 300 ohms or 450 ohms or whatever.

The factory channel master feed is nothing more than a open wire feed line

Just make sure they are in phase and that both feeders are the exact same length.

mcclapp: when I said "impedance", the earlier suggestion was to do with the balun (as in, if the impedance is no longer 300 Ohms when joined together, a different balun might be necessary)

Where I was going with my last post was to say that the impedance will be all over the place depending on the channel it will vary from below 100 ohms to over 500 so 300 ohm, 450ohm or what ever won't make much difference in the average gain.
It will make a difference where the peak is since it will change where the best impedance match is, as will changing the length of the feeders.

Using 2 baluns and a combiner will be about the same since each antenna isn't 300 ohms over the range of tv frequencies the baluns will convert the feed point impedance to some impedance other than 75 ohms which will cause a mis-match to the coax.

Either way you won't find a solution that will be the best for all the channels but maybe you will find a combination that will work best for your channels.

Newbie here.

I came across a post on this forum created in 2001 that had a picture of two 4 bay bow tie antennas on one pipe. It did not show how you connected them. I have an 80 year old brother trying to get a better signal for his digital converter asking me questions I cannot answer. How the two bays connect is one.

Do the wires run parallel or cross?

Where does the connection to the converter tie in?

I appreciate any help. For some strange reason I cannot find this on Google (which means I'm probably not Googling the right thing).

If the answer is another thread, or there is a step-by-step for doing this on the forum, please link to it. I can read and comprehend, I just can't find!

Thanks!

Hi Tek_Freek and welcome here - look through this thread for info on how to get started with your antenna combining research. Above all see the OTA FAQ and especially Post #16 in it.

I want to connect 2 4221 clones together (one one pole on my roof) so I can face one towards the CN tower and one across the lake to Buffalo. Any advice on what I need to properly merge the signal into one cable? Would a basic tv splitter work? I am not concerned at all about analogue stations. I just want HD.

I have one 4221 hooked up now facing buffalo and CTFO, CTV, SUN TV have break ups.

Location is Whitby and I can see the lake and the cn tower from my roof.

Went out to oshawa to see someone trying the same thing 2 clones , i just put up a genuine channel master 4221HD instead and got toronto and buffalo there is a difference between a cheap clone and an original! you can use help in this forum and other places to build your own antenna that will out perform a cheap clone! Even a coathanger will get you CBC in the GTA area! I would not waste time on cloned antennas. If you want to stack them there is enough info here just do a search for stacking antennas in this forum!

4-bay bowtie reflector antennas may resemble each other, but they can differ quite a bit in actual performance! :eek: What may seem like a bargain in a store may turn out to be a pain. Its possible that one CM4221HD may do the job, but since you already own your antennas we need to keep in mind that some situations call for 2 or more antennas no matter which ones you've got (sterney, the thread covering Whitby (http://www.digitalhome.ca/forum/showthread.php?t=36538) shows a wide variety of reception conditions east of Toronto). A read through of Post #16 in the OTA FAQ will walk you through the necessary steps.

Option 1: Get a rotator. They were designed for this.

Option 2: Get a splitter/combiner and combine the 2 antennas. May cause Lots of interference issues. Where the TO stations knock out the Buffalo Stations.

or

Option 3: Use a switch box. Run 1 cable from each antenna to a switch box. When you want to Watch TO. Setting 1. When you wanna watch Buffalo. Setting 2.

Good Luck,
Al

Just stack them on a long pole lots of examples here seen the latest pimp my gear thread in this forum. use exactly the same length of cable and a good quality splitter!