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Old 5-Jul-2013, 1:48 PM   #37
tripelo
Senior Member
 
Join Date: Jan 2010
Location: Dallas, TX
Posts: 173
Quote:
Originally Posted by Pete Higgins View Post
That’s interesting, I assume you derived your measurement through empirical testing for channel 13?
Yes.

The signal strength of the combined stack was observed on a signal level meter while the lower antenna was moved up and down by approximately +/- 18 inches.

Interesting about Winegard recommendations, in that they list two recommended stacking heights.

In general, the wider spacing (around 1 wavelength) yields higher gain for a given channel.

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On the stacking gain topic:

In recent years, read several accounts of unsatisfactory experiences with vertical stacking.

Stacking two antennas for gain (horizontally or vertically) requires near equal illumination of both antennas (equal signals). If the two antennas do not receive equal signals, then the situation tends towards the two-antenna situation discussed earlier. The antenna receiving the weak signal tends to load the strong one and either loses signal in the combiner or re-radiates signal.

The above scenario more likely occurs with vertical stacking as compared to horizontal stacking. The sub-optimal effect on vertical stacking is mainly due to layering (signal reflection from ground, or diffraction from an elevated edge). To equalize the received signal in each antenna, it is usually necessary to have them mounted high above ground, so high that layering affects both antennas about the same.

How high is high enough for effective vertical stacking? Don't know, depends.

In many cases, probably high enough that the spacing between the antennas represents only a small fraction of the height above ground (could be 10 wavelengths or more).

Unequal illumination is related to another factor that has a role in producing less than expected gain from vertical stacks. That factor is vertical angle-of-arrival of received signal.

Stacking antennas may have some advantage (space diversity) other than increasing gain.

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Quote:
My TV tower rotor is an NTE ECG U106 with a TB-105 thrust bearing ~ 2.5’ above it.
What are your impressions regarding the NTE rotator, compared to the Radio shack rotator?

Quote:
...Channel Master was one of the premier brands here from the mid 1950’s through the late 70’s or mid 80’s...
Interesting that Channel Master was into California that early. Many of the antenna manufacturing companies in those days were sort of regional. Seems as if Channel Master must have had the best (Quality x Performance)/Price ratio of all manufacturers.

Quote:
...when it seemed like their antenna quality and customer service really declined...
Probably about the time when satellite-fed cable was coming on strong.

Last edited by tripelo; 5-Jul-2013 at 2:16 PM. Reason: typo & comment
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