|Originally posted by bmello
Mike, any luck with the Hughes E-86 or DST-3000? How about the Panny?
The customer with the E-86 didn't have me add the second antenna line (would have had to pull a second coax through 70 feet of 3/4" I.D. conduit), so that one will have to wait. I recently installed a Sony HD-100 with two separate input lines, one labeled for cable and one for antenna, but its "automatic" add channel procedure made me choose between one input and the other. I was hoping that I could use both and that the "capture range" of the cable TV input was wide enough (2Mz) to capture the nearest UHF broadcast channels on that input, but it wouldn't let me.
Funny thing about antennas not connected to one another. I service a fourteen story high-rise in McLean, Virginia, maybe ten miles or so from most of the Washington, DC transmitters, where they keep building taller buildings "behind" it and I have to keep relocating the antennas. They used to have cheap (discontinued) Channelmaster single channel antennas for channels 7 and 9 on the same mast. Then, when another building went up, they developed a little bit of a ghost, so I replaced the 5 element channel 9 antenna with a ten element 7-9 antenna and the improved front to back ratio made the ghost image subside. I also noticed that the channel 7 signal coming off the 7-9 antenna was a little better than off the cut-to-channel 7 antenna, so I made that new antenna the source for both channels.
One day, I decided to clean up the antennas at this headend, and I removed the old, abandoned channel 7 antenna . Before I even left the site, however, one of the residents called the management office to complain that her channel 7 reception had just become terrible. To make a long story short, I determined by measuring from the 7-9 antenna to the rust line formed where the channel 7 U-bolt had been clamped that these two antennas had been exactly one half wavelength apart. Like, within half an inch. And they had been resonating in such a way as to improve the front-to-back ratio of the 7-9 antenna's channel 7 reception, so I had to put the junk antenna back on the mast to restore the picture quality.
In an unrelated fiasco, I once tried to improve the signal quality of channel 8 from Richmond Virginia at a multifamily dwelling in Charlottesville (maybe 60 miles away). I tried stacking a second Blonder-Tongue ten element channel 8 antenna, but the picture did not improve. Because I was working at the top of a 40 foot ladder on a roof that was not flat, I didn't bring a test TV up with me, which makes this kind of work very difficult. Instead, I had a reliable guy watching TV indoors and communicated with him by walkie talkie. When I finally told him I was giving up, he replied that I had just made things better than they had ever been. Well, I hadn't deliberately done anything. Again, to make another long story short, in shuffling different combinations of cabling around, I had inadvertently misconnected one of the stacked antennas to the wrong side of the two-way splitter/combiner, making of one the antenna inputs twenty or so dB weaker than the other and messing up its linearity as well, AND I was standing "inside" the lower of the antennas, meaning I was physically interrupting the signal at the same time, and that combination of errors produced by far the best quality picture.
I later figured out that the most significant contributor to the reception problem was one or more weak FM transmitters that developed harmonics on channel 8 (91.1Mz, 91.9Mz and 92.7Mz are all within a couple of miles) and my ill conceived "stack" was somehow mitigating them.
The reasons for sharing all of this with you are to show that stacked antennas can interact with one another in different ways that are not always predictable, that the fact that something worked well for you does not mean that it will work for anyone else (a lot of people are getting excellent reception from Terk antennas, for example) and none of us ever know so much about developing multiple antenna arrays that we can't benefit from getting lucky now and then.