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Discussion Starter #1
Question.

I just obtained a CM 3023 UHF yagi. I've noted in other message strings that you can achieve more gain by adding a sheet of hardware cloth or something similar to the reflector screen on the back of other antennas like the 91xg.

Could I see a similar improvement in gain with this antenna if I add something like hardware mesh or galvanized chicken wire behind the screen? I need the most gain for an occasional catch on Ch. 17. I can pick up some 1" by 1" chicken wire for next to nothing at a local farm and home shop. I figure if I can get another DB of gain on the low end of the UHF band it might be worth a try.

Your thoughts?
 

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A tip for our members: the Channel Master 3023 might be hard to get information about these days but the later CM4248 model number describes the exact same antenna when fully assembled. :)

The thing about chicken wire is that you don't want the hexagonal stuff - the wires need to be mostly horizontal. The most useful mesh is often called "corn crib" fencing or "welded fence": http://www.digitalhome.ca/forum/showpost.php?p=1084891&postcount=273
 

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Yep, modeling has shown that 1" hex chicken wire is about equivalent to 2" X 4" mesh at channel 38, with a lot more wind resistance.
 

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I wrote the wrong dimensions for corn crib mesh earlier - it is usually 3" x 2" or 4" by 2" in precut rolls, although some stores sell it off the spool by the foot or metre.
 

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I need the most gain for an occasional catch on Ch. 17.
1" X 2" mesh only offers a tiny gain increase over 2" X 4" mesh on channel 17. On channel 51, the gain increase is much larger with the smaller mesh size.
 

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I believe your ION 51 is on real channel 23. Give it a try, it should help some.
 

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I put the chicken wire up and well... not sure.
I used 10 square grid and put it right on the back of the 4221HD

Turned on the TV and it seemed that allot of the chanels were up to 98%.
But, I lost 49-1 and 2. Did nothing for ION.

Took it off and got 49 back but, still, most of the other chanels were still at 98%

I don't know what to say. I thought it would have worked.

oh well.... any ideas?
 

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I put the chicken wire up and well... not sure.
I used 10 square grid and put it right on the back of the 4221HD
Im not quite sure what you did. Is that a 10" X 10" piece or 20" X 20" piece ?
Post your TVFool again.
 

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CM4248 15-ELEMENT FD-YAGI with ALTERNATIVE CORNER REFLECTORS:

Ken Nist posted a model of the CM4248, presumably based on his own Measurements. Many years ago user <300ohm> imported and adapted the file to run under 4nec2. The CM3023 is reportedly similar (if not the SAME) as the CM4248.

After tweaking for AGT=1.0, I posted 4nec2 Results....comparing the Original with 14 Reflector Rods (RR's) in the Corner Reflector to an alternative (b) with 12 RR's (same Width) inserted half-way between the existing 14 RR's and an alternative (c) with a pair of (nearly) SAME SIZE Reflector Screens (with 1x1-in Grid) replacing the Original 14 RR's. I also ran models with WIDER RR's and WIDER Screen Grid, but found that the Original 33-in Width was very close to OPTIMUM already, with Gain being reduced (esp on higher freqs) as the Corner Reflector Width was increased:
UHF CM4248 15El FD-Yagi + Corner Refl's

NONE of the alternatives provided more than an insignificant improvement on Ch17 (491 MHz) compared to the Original.....and only provided as much as about 0.5 dB improvement on the highest channels...which is probably TOO SMALL to notice much difference in live watching conditions. So if you're looking for SIGNIFICANT improvements, consider a modeling Optimization exercise to determine BEST dimensions for a BOOM LENGTH EXTENSION (1.5-3 dB more)....or BETTER YET, consider using a PAIR of MATCHED STACKED Antennas for 2.5 dB to 10+ dB Space Diversity Combining Gain:

 

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Discussion Starter #13
Hollands. Thanks for resurrecting the old thread. Forgot about it. Not going after Ch. 17 at the new location but instead looking at channels in the low 20's.

What is the best way to combine two of these with minimal to no loss? No point in using a coupler that will lead to 2.5 db in loss since that will offset the gain by adding the antenna.
 
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