Thread: Rca ant751
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Old 22-Apr-2017, 8:00 AM   #26
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Rca ant751

I found an initial answer to the question I posed to rabbit73 above regarding how the "new and improved" RCA ANT7511 would compare to the previous versions of the ANT751. It was a reply from holl_ands on the AVS Forum in a thread on the antenna subsection back on 12/28/2016. Here is what he said:

IF you provide detailed Measurements and multiple PHOTOS (incl. a RULER in the Photo), then I can TRY to model ANT-7511 ES (or most any other Antenna of interest). But I haven't published 4nec2 Results for ANT-751 because Log-Yagi's (ditto YA-1713) do NOT model very well on the upper frequencies wrt Gain and SWR for ANT-751 was "off"....I suspect I need pricey NEC4 Engine to model the Cross-Over Feedlines and hopefully eliminate these shortcomings.

UHF portion of ANT-751 and ANT-7611 ES are SLIGHTLY different...but not by much and SAME number of UHF, probably about the same UHF given in Spec Sheet for HD-7000, from which the UHF part of ANT-751 was derived:

My simplified 4nec2 model for the ANT-751R/EZHD calculated 6.3 dBi (Minimum at band edges) to 7.5 dBi (Max Mid-Band) Hi-VHF Gain. When I removed the most forward Hi-VHF Director to emulate the ANT-7511 (although without SAME Element Spacings) it is reduced to 5.6 dBi (Minimum at band edges) to 7.0 dBi (Max Mid-Band). So only 0.5 to 0.7 dB reduction in Hi-VHF Gain.

FYI: Slightly higher Hi-VHF Gain numbers (esp. on upper Channels) were found when I OPTIMIZED 3 and 4-Element Hi-VHF Yagi's [which tend to provide more Gain than Log-Yagi's, esp. on higher frequencies], using Folded-Dipole Active Elements designed for Hi-VHF Band....rather than going THROUGH the UHF Folded Dipole Active Element, as done in the ANT-751 Log-Yagi [UHF Dipole and TWO Hi-VHF Active Elements form a 3-Element LPDA structure]...which is clearly causing some minor degradation, esp. on Ch12/13:

Here is where I actually found the above comment:

So it appears from his findings that there is a small loss in gain from the RCA ANT7511 to the ANT751, if I'm reading him correctly. Any thoughts?
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