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Originally Posted by teleview
... does not solve the problem of multipath when the antenna panels are aimed in different directions. ...
... does not solve the problem of signal power bleed off of signal from one antenna panel to the other antenna panel when the antenna panels are aimed in different directions...
A modified directional coupler is one way to somewhat solve the problems , however there is a big signal power loss (dB) when using directional couplers.
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And not because I do not know any thing about the subject.
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It sounds like you are arguing against claims that have not been made. I don't see any claims that would suggest multipath has been eliminated, dealt with, overcome or solved... I see no claims of zero loss or perpetual motion. I haven't even seen a claim that the DB8E has perfected cold fusion.
The manufacturer's documentation is the most complete I've seen from any antenna builder... and it's clear, that if you opt to aim the panels in different directions, directivity and net gain will be reduced. It follows that one should not expect the split aim configuration to be impervious to multipath. Having said that, I fail to see any reason to be critical of the design or the detailed technical specifications provided. As with any other antenna from a reputable manufacturer, this is not a 'one size fit's all' solution and the antenna is not being promoted as such. I see a very well built high gain UHF only antenna, that has a well documented feature set that can provide an outstanding reception solution when properly spec'd and installed.
In theory, ganging two identical antennas would offer a gain increase of 3 dB. There are inefficiencies in the real world, so achieving 2 dB or more gain when ganging is doing well in my book. Given the credible gain specifications of the DB2E (12.0 dBi) and the DB4E (14.5 dBi) the engineers at Antennas Direct have done very well... achieving a net gain of 2.5 dB by ganging two DB2E arays. The results for the DB8E are even more impressive, at 17.4 dBi Max Gain, the combining networks incorporated into the design of the DB8E are doing extremely well... I see no evidence of "...signal power bleed off..." or "... big signal power loss...".
In the end, should one find they are beset with multipath, they have the option of cabling each DB4E section separately, and using an A/B switch or an axillary HD capable STB tuner.
http://forum.tvfool.com/showthread.php?t=2882
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Circuits A and B preform the same functions.
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Yes the function is the same, impedance matching and interfacing balanced to unbalanced... but the micro-strip-line has slightly less loss in it's designed frequency range.