Originally posted by Everton66
The antenna I am currently using successfully is a Radio Shack 15-2160 and has these specs
UHF Band Chan. Average Gain:.........................................9.5 dB
Median Av. F/B Ratio:.............................................UHF 14 dB
I thought the DB4 would be an improvement on that, but the web site only lists maximum gain (13.5dB) and as you have pointed out a useful 11dB. I don't want to get much bigger than the CM4225. If I am not gaining much then I will probably leave as is and try combining two of the same.
I think Radio Shack's numbers are usually highly inflated. Knowing the 15-2160 as I do, I'd be surprised if it has 9.5 db of gain on any frequency. More likely, it's a 7-8db of "real gain."
Joining two identical antennas together in a stack will get you no more than (and probably slightly less than) 3db of gain. It will get you a hefty increase of front-to-back ratio as well as a significant decrease in beamwidth. Those are good things, no doubt about it. But they're going to be larger than 1 4228 or DB8, because you're going to have to mount them a minimum of 30" apart.
If you're pointing the antennas in different directions to receive stations in two areas, it doesn't matter if they're the same, different, red, green, blue, or coated in a special polymer. They're going to mess each other's signals up unless you use a Jointenna or similar filtering mechanism. You can get cable lengths perfect, place them perfectly, and still have them mess each other up. I've said it a million times and I'll keep saying it until I'm blue in the face: You cannot combine two antennas designed to receive the same frequency, point them in different directions, connect them via a simple splitter/combiner and *expect* to get good results.
So I guess, in the immortal words of Clint Eastwood, "Do you feel lucky?"