TV antenna question - not a Tablo problem

For me, the combiner brought in 3 pixelating stations much more clearly and had no negative effects on the other channels. I only utilize approximately 10 stations - all networks, a couple of PBS stations and a couple of old movie stations.

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In an antenna stack, two identical channel\frequency signals will sum up. That is if the two antennas are joined by equal length coax cables and facing the same way. This is known as a gang (horizontal joining) or a stack (vertical joining). If the cables are of different lengths, the two identical channel\frequency signals will subtract from each other. The equal length cables ensure the signals are in phase, which they have to be in order to sum up. Usually the second antenna in a stack adds 2 to 3 db to the overall signal.

If each antenna picks up different signals in a gang or stack, the strongest signal of a strong-weak pair will predominate.

If the two antennas are facing different ways to pick up different channels, the cables can be of different lengths.

Two antennas can be joined by a channel selector such that each antenna only brings in the specified channels. A splitter costs $2; a selector $20.

Here BTW is a picture with details of a stack (which I built) designed by someone well known in the OTA community:

http://imageevent.com/holl_ands/stacked/horizontallystackeduhfantennas/horizstkff6vdarhhh

What does it cost to build a stack? Mine cost less than $20 ($8 per antenna) with materials from Home Depot and twice as powerful as any $100 antenna one can buyā€¦

BTW youā€™ll notice that the antenna designer has run simulations using software from the US Navy freely available to analyze its architecture and performance (no hocus pocus). I was able to customize the antenna dimensions specifically for the frequencies I was interested for my area. Why have a generic antenna to pick up non-existent frequencies when the antenna can be molded to optimize those frequencies actually used in the area? Especially if there are hard to pick up channelsā€¦ As I indicated in another thread, there is a wonderful picture of an antenna ā€œfarmā€ in someoneā€™s attic (Toronto) with DIY antennas arrayed to pick up channels from the Ontario and Buffalo areas.

Incidentally since signals can subtly shift over the course of a day or season by several degrees, multiple antennas, having a wider coverage area, will pick up these shifts.

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The biggest issue with using a combiner is that on a particular channel given the individual lengths of your coax, you might combine two signals that are out of phase in a manner that will cause them to destructively interfere, which will of course diminish the effective signal at your receiver.

If this occurs, you can play around with length of the coax between your combiner and one of the antennas. Also, if youā€™ve got one antenna pulling in relatively strong signals in one direction and other antenna pulling in weak signals in another direction, you can try putting an attenuator after the antenna pulling in strong signals, just before your combiner.

One doesnā€™t have to use coax cable with a combiner. I used ladder lines (450 ohm) to connect the two antennas equally in phase. This eliminates the splitter\combiner and trying to get equally sized cables.

For those combining antennas but interested in different channels from each antenna, this site has affordable channel selector\antenna combiners (convert from Euros to dollars):

http://www.antenne-komponenty.eu/english/main/product/zlucovace.html

I use the purchased Winegard FL5500A and it is the best indoor antenna Iā€™ve found for me. It is designed for both VHF and UHF. The VHF (broadcast - virtual channel UHF) is in Killeen , TX and Iā€™m in north Austin, TX. I do lose them during heavy rain, but otherwise they are good. Location is very important - did not come in in the living room, but do in the bedroom window.

Which one did you get, and how did it do?

Are your two antennas running the same cable length to avoid interference, or is it performing well with different length cables on the antennas?