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Old 1-Jun-2015, 3:57 PM   #1
rickbb
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Join Date: Dec 2014
Posts: 281
4 bay out performs 8 bays

Kind of a long post, I apologize for that.

http://www.tvfool.com/?option=com_wr...f1f063131b14c3

Spent a weekend experimenting with my reception dilemma. Used 2 mast locations and 3 variations of the Mclapp M4 and M8 antennas.

I tried 3 antennas, my current DIY M4 10 x 9.5, a new DIY vertical M8 10 x 9.5 and a “twisted” M8 10 x 9.5. All using Mclapp’s designs. I got the twisted design from a NEC simulation I found on a site from holl_ands. (The top 4 bow ties are aimed at 90 degrees to the bottom 4 bays to take advantage of the null zones of each 4 bay panel.)

I combined the 4 bays on the M8’s 3 different ways, one with dual baluns and a splitter reversed, one with identical lengths of 300 ohm feed line and single balun and one using instructions for co-phase lines for vertical M8's on Mclapp's web site.

I have the situation of having 3 main directions to receive from. 2 are almost 180 degrees apart so my DIY M4 gets both of those directions just fine. The third direction is almost 90 degrees apart from the others, and in the RF shadow of 2 large Maple trees in my front yard. Hence my problem and experiments.

I knew I needed a different location so I mounted a new 10 mast on the other side of the roof line, 16 feet west from the current mast point and 10 feet north. This would give me a clear shot around the trees to all broadcast directions. Height was about the same 25 ft. AGL.

The results? Reception was worse overall for all antennas at the new location. I got greatly improved signal from the SSE towers since I had cleared the trees from the line of sight. The towers from the west were the same as before, but the towers from the ESE were all way worse. A few even gone completely.

Tried all 3 antennas back at my original and current mounting point and signals were back to where they have been. The funny part is my M4 outperformed both versions of the M8 in both locations. I will go back over the construction of the 8 bays to make sure I haven’t made some mistakes in spacing, etc.

I wound up just putting my M4 back and adding 6 feet to my original mast height and improved signal quality from the east quite a bit. Signals from the south, behind the tree, are still dropping out on me. When the wind blows it’s so bad it’s unwatchable.

I have 2 more locations on the roof to try, I’m guessing that perfect looking spot wasn’t so perfect after all.
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Old 1-Jun-2015, 6:06 PM   #2
rabbit73
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Quote:
DIY vertical M8 10 x 9.5.....I combined the 4 bays on the M8’s 3 different ways, one with dual baluns and a splitter reversed
With the vertical M8 that was not twisted, and fed with dual baluns and a splitter reversed, did you try reversing the 300 ohm wires on ONE of the baluns to see which way was better? When the two M4s are properly phased together you get one main lobe for increased gain. When the two M4s are not properly phased, the main lobe splits in two, with a null between.

When you use the vertical stack of two M4s the vertical beamwidth is greatly reduced; the horizontal about the same as an M4. I have found that is often necessary to tilt even a single M4 for max signal while watching my Sadelco signal level meter.
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Last edited by rabbit73; 1-Jun-2015 at 6:22 PM.
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Old 1-Jun-2015, 9:21 PM   #3
rickbb
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Yes, I reversed the 300 ohm lead on one M4 for both the dual balun and single balun setups. Signals seemed the same to me, still slightly less than the single M4. But I don't have a decent signal meter, have to use either the TV or Windows Media Center's signal meter.

I thought about the vertical beam width but didn't really make any plans for a way to adjust it on the mast. Something I'll have to correct on my next go around with it.

Making all the changes and adjustments on a hot roof, (and going up and down the ladder several times to get the tools I forgot), was a bit of a challenge. So I may have missed some of the finer points of aiming and switching the feeds around. Especially when it was on the high side of the house up a 10 foot mast.

I've got a feeling that either the vertical angle needs working on, or I have messed up on the measurements on the phase lines, or both.

Even the setup with the Mclapp co-phase lines to combine the 2 M4 panels, it seems to have the same signal quality as the 300ohm single balun setup. And still slightly less than the M4.

The channel that drops off the most is WRAL, it's gone from both M8's but good to strong on the M4. I also lost my Roanoke channels, (virtual 7 and 10), but those are hit or miss most days anyway depending on weather.
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Old 4-Jun-2015, 5:06 PM   #4
Jason l
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Join Date: Apr 2014
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m4 better than m8

I did tests with the 10-9.5 m4 and m8verticle 10-9.5 the 8bay beet the 4 bay always on the very farthest uhf channels. And yes I had to tilt the 8 bay slightly more at less height and less at more height. The 4 bay didn't change much for me from tilting it.
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