Thanks so much for your reply.
Quote:
Originally Posted by Tower Guy
In order to determine the advantage of stacked antennas you should add 2.5 db to the gain of a single antenna. But even then the spacing must be optimum, which can't be true on all channels at once. Next you SUBTRACT the 3 db noise figure of the 7777 preamp. The gain of the preamp can overcome the loss of the coax and splitters, but never add to the NM.
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Well, I do have a Kitz preamp that advertises a lower noise figure and nominally higher gain...but the CM actually pulls in more stations when I do an A/B comparison.
Is NM the
only determinant of "viewability", or is the dBm equally important? Is NM stated in terms of a dipole reference? In that case, stacked Yagis should give you something better than10 dB extra martin, right? (Sorry for the newbie questions, but NM is a new term for me in this context.)
Quote:
Originally Posted by Tower Guy
As for the low power stations, most of them are on low band VHF. Perhaps your stacked yagis are not intended to receive channels 2-6.
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Nominally, they are full-VHF band...but none of the elements is longer than 40 cm so it's not going to have a bunch of gain down at 80 or even 60 MHz...but it won't have zero gain. With the NM of the repeaters (and a couple of them are LOS) I'm not understanding why I don't see their signal. Of course, I don't have a spectrum analyzer so I only have the TV to go by...
[/QUOTE]Next, verify your location using the online maps scheme.[/QUOTE]
Did that, the system places me correctly in the terrain. But the signal analysis indicates I should be "seeing through hills" that have me in the shadows for sure.
In particular, channel 3 (second item on
the report) has a huge NM and PWR rating...so it should be screaming thru, right? Yes, there's an overlap of a weaker signal (sixth one down in the list), it's 30 degrees off in azimuth so nicely attenuated in the antenna's side-lobes. Similar story with channel 6, third one on the list.