Bent CM 4228

[rjs0905]

So I was replacing the mast on my OTA HD antenna, which consists of 2 CM 4228's mounted one over the other and connected together, and despite the greatest of care, I dropped the mast and bent the heck out of the 4228's. One got it worse than the other, but both were bent up to some degree.

I unbent them by hand as best I could, but even though they look OK, they are still not totally right, in that most of the components are no longer completely 100% plumb and level (i.e., the screens have some small amount of wave and curve to them, the bowties are slightly out of plumb with each other and the screen, crossbars have a very small bend in them in the middle). Because of the way the antenna is constructed I found it pretty much impossible to get the assembled antenna hand-bent back to its 100% original condition.

The unit basically works, although I can't really tell whether I'm getting the same level of signal and performance as before the "accident." I haven't tried to disassemble the antenna (i.e., pull the screen off the bowtie assembly), get out the tools, and try to bend everything back completely true and plumb because I'm not sure whether it would be: 1) possible; 2) worth the effort. Anyone have any experience with this or have an opinion on the degree of "foregiveness" here - As with horeshores and hand grenades, does "close" count with antennas?

 

[KSbugeater]

My bowties aren't all aligned anymore and my installation has introduced some warp to the grid, but the thing still works great. Like you, I'm curious to know if it would work even better if aligned perfectly. I'm guessing not more than 5% better.

 

[bhelms]

Interesting posts, as in "been there, done that"...! Not the same situation, but it left me with essentially the same questions. No doubt, changing alignment of the components in an array changes the reception pattern. But unless you have a means to measure that and some baseline for comparision then it's about impossible to answer the question of whether or not the performance has changed much. Assume it has. But some points to consider: 1) out-of-the-box these assemblies aren't perfectly aligned, so there is certainly some variability that the manufacturer allows that would make any two units have slightly different performance, and; 2) you apparently have acceptable performance with your repaired units, so I wouldn't do anything more until/unless you notice a change for the worse. Who knows, you might have made them even better than they were originally! I'd leave well enough alone for now until you have some time to see if there were any noticeable changes...

 

[Barry Erick]

On digital, signal level doesn't mean a thing until you get too close to the threshold or introduce too much mutipath by the bends. If you have an 80 level now, it won't look any different than a 95 did. Down to a 55 and you'll start to see errors. If analog, it means a snowy and ghostly signal as it gets lower.