Originally Posted by Larry Kenney
You guys down in the South Bay, Turbo and Xn0r, might also be close to that infamous cliff edge and you might be seeing the effects of the changing conditions right now.
There hasn't been a lick of rain here in Sunnyvale for over three days, so my personal "cliff edge" had more to do with the drips of water which came out of the matching transformer at the antenna when I took it down today. Here's the heart-stopping, edge-of-your-seat story...
I was comparing the signals today to what I "normally" get, and noticed that KRON was now at 0% signal. I was contemplating the theory that I had a problem with UHF, but it didn't completely add up. 44 had gone from 86% down to about 68%. But channel 54, which should have roughly the same signal strength where I live actually increased
from 67% to 83%, and it's transmitter is over in Fremont, 90 degrees east of where my antenna is pointed, and
54 is even higher up in the UHF spectrum than 44. Normally, with my antenna left pointing toward Sutro, 54 over in Fremont was on the bad side of spotty, but when KTEH transmission began on 9-2, I just left 54 behind. But since most of my signals took a dump this last week, 54 miraculously increased in strength, with no break up. KICU also increased from 86% to 92%, and it's well up there in the UHF, too. So the notion my problem might be UHF-related had pulling my hair. Realizing that there's not much left up there to pull, I needed to find the answer before it was too late.
So, I figured I had to go through the motions of at least pulling the antenna down for a look-see before giving up. I just couldn't see anything wrong with the elements, nor did I see much that could
go wrong with the front of the antenna. I examined the 300-75 ohm matching transformer. I was admiring my stellar job I had done at waterproofing the coax-to-transformer connection. Silicone around the coax, followed by heat shrink tubing and zip ties at each end. Then more silicone around that, then larger heat shrink tubing around the end of the transformer's shell and over the coax, followed by more zip ties at each end. I and my imaginary friend were nodding in unanimous approval, when I felt a drip of water come out the other end, where the 300 ohm flat lead enters the transformer's shell. Umm, well, it looked
sealed from the factory, so I had completely ignored that end! But what looked sealed was simply a seam, and it was finally breached. I took the transformer off and puffed into the coax connector, and the fountains of Rome came spewing out the other end. The contact was rusty. The resistance measured anywhere between 13 ohms and 200 ohms, depending on how I pushed and pulled the lead. Do ya think, maybe...?
So I installed a good used transformer and sealed both
ends, thank you very much, with coax seal this time. And of course, the new transformer solved the whole problem. But, now I am left with new confusion. Recall channel 36 and 54 that had miraculously increased in strength, while most others took a nose dive. With the installation of the new transformer, the signals on those two channels dropped back down to "normal." With the rusty transformer, 54 was barreling in at 83%, but with the new transformer, it's back down to 62% and spotty. Likewise, channel 36 loved the rusty transformer, with a signal of 92%, but dropped to 82% with the new transformer. Can anybody explain what strange things lurk in such a simple device that could cause such unexplainable behavior? And why did the analog signals seem to come through the crapped-out transformer normally?
Just FYI, the signals for all the channels I watch, before and after transformer replacement, were/are:
2: 33% & 92%
4: 0% & 79%
5: stayed at 100%
7: 79% & 92%
9: 87% & 92%
11: stayed at 100%
20: 83% & 86%
36: 92% & 82%
44: 68% & 100%
54: 83% & 62%
I have a question about exactly which element(s) on my antenna deal with UHF. I have the UHF/VHF combo, with the large section composed of many long elements arranged in a chevron pattern. At the other end are smaller elements arranged in a vertical fan tail configuration. Jutting out from the center of this fan tail is a horizontal piece with very small elements along it's length. And where all three of these different pieces come together, is a teeny bow tie element about as big as, well... a bow tie. Is this little bow tie element the only part that pulls in UHF, or do the vertical fan tail and horizontal sections on the rear also contribute to UHF reception? God, if it's just that puny bow tie element, I'm amazed I pull anything in, and can only imagine what I could get with a nice UHF antenna.