Yes you are right, I learned that 10 years ago. I learned to collect 1 balun to the left 4 bay side first then check field strength meter on TV. It turns out swaping wires on 1 balun gives a high & low signal, I did not expect that. With left side balun connected for high signal then connected right side balun and swapped wires on the right on it for best signal. With right side balun connected to T combiner high signal antenna produces the best signal on the field strength meter. I learned testing a weak signal is many times better than testing a strong signal because antenna improvements are often not noticed when already having a very strong signal. This antenna is 10 years old time to clean it up and test all the parts & make improvements. I like the antenna close to the ground so I can work on it but after getting it working better I want it higher up. I found this antenna in my amateur radio antenna book. There are no 2:1 baluns to be found and no plans to build one either.Another thing that occurred to me is that comparing the two feeding arrangements you show in your first post, one advantage of using open wire feeder to combine the arrays:
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is that you know that you are combining the two arrays in phase. When you use separate baluns like this:
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you run the risk that unless the baluns have some sort of polarity indicator (and the ones I have seen haven't), there is a possibility that the signals are out of phase. You should compare the received signal strengths with the connections to one of the baluns swapped and choose the arrangement that gives you the strongest signal. Do this for each pair of bays to ensure that each pair is working properly. When you then add the two pairs together, you need to again ensure that the signals are adding in phase. You can check this by reversing both baluns on one pair and see what happens to your combined signal strength.
I already have that. I am trying to reduce losses by eliminating 5 coax cable connects, T combiner, 2 baluns.Essentially what you're trying to do is combine two aerials into one - which gives you extra gain, by making the complete array more directional.
This is usually done with a 'phasing harness' - essentially three pieces of coax (of specific sizes) connected in a Y shape.
And is it accurately calculated and constructed? - you can't just stick bits of old coax together, it needs to be accurate, and presumably without spurious joins?.I already have that. I am trying to reduce losses by eliminating 5 coax cable connects, T combiner, 2 baluns.
When I built my first antenna years ago I copied the CM4228 antenna, I assume factory antenna is correct it works? Somewhere I read coax from each 4 bay should be 1/4 wavelength each, 2 coax 10" long are 4" too short the 4 bays are 24" apart, I can not find that information now. I'm not exactly sure when calculating antenna MHz do I use total dipole length = 1/2 wave length or the length of 1 element = 1/4 wavelength? If I can make the 2 coax 1/2 wave length they will be long enough.And is it accurately calculated and constructed? - you can't just stick bits of old coax together, it needs to be accurate, and presumably without spurious joins?.
They were available ready built from the aerial manufacturers, for combining either two or four aerials to provide greater gain.
Yes......if you compare 8 bay TV antennas CM4228 and DB8 to ARRL 8 bay antennas electronic rules do not apply. I hate to waste time building another copy of CM4228 and still have the same thing I already have. I wanted to build an antenna with only 1 balun but someone said, impedance matching works best like the antenna I already have. Only improvement I can actually make is build a new antenna with plastic frame not metal and use plastic screws not metal, maybe I can eliminate 2 coax connectors by soldering coax cable directly to the copper antenna wires. Putting antenna up another 10 ft higher might be better than trying to make improvements or build a better antenna.Defining things in terms of wavelength only works if you are dealing with a single frequency or a very narrow range of frequencies. You are trying to over a wide range.
I have read this several times and still trying to figure out what it is telling me?You need a fairly broadband antenna to cover the UHF channels (510 - 640MHz), and you want to throw in a couple of VHF ones as well, down to 79MHz.
This means that you have to be careful in taking a narrow-band design, like that ARRL collinear, and using it for likely dimensions. Spacing to planar reflector - I'd suggest quarter wavelength or a bit less at the bottom of the band, but this is a starting value - it's a trade-off over the range. I could make similar suggestions on element lengths, spacings etc.., but in an array all these things interact and the only real way to know what is going on is to build and experiment or to simulate. If you just pick likely numbers for each parameter it will work in some fashion, but you would be lucky to get the best gain for your effort. I'd look for published designs, preferably with measured gains, or reliable simulations.
There seems to be a reasonable amount of activity out there with folk using antenna design tools to simulate and try to optimise this sort of design, over the frequency range you want to cover. e.g.
User mclapp on that thread is doing NEC simulations of his designs and seems to have a reasonable number of happy devotees building his designs. The sort of data he produces: https://imageevent.com/holl_ands/multibay/8bayrefl/cm4228hdmod
is the sort of thing I'd expect from this sort of simulation, so maybe his results are trustworthy. No guarantees, but I suspect there are others out there.
As far as the reflector material is concerned, you need a good array of horizontal rods. At the top of your band the wavelength is about half a meter, so you don't need the rod spacing any less than lambda/10 = 50mm (2in). You do need continuous horizontal rods though (and not too skinny), whether these are held together by a few or many vertical ones is simply a construction preference.
The only data I have is from an old copy of Jasik (Antenna Engineering Handbook)
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So these do provide useful broadband gain, but he does omit to tell us the spacing to the reflector.