Quote:
Originally Posted by Ronbo
Well the old station channels corresponded to an actual frequency i.e. ch 4 was the same frequency everywhere.
On over the air you have ch4-1, 4-2, ect but they aren't on any specific frequency, it's a VHF channel on the old system on ATSC it's what ever frequency the FCC assigns and likely a UHF frequency. Your TV treats the old channel number like the call sign. (WGBH) Basically makes the transition easier for people ch4 is still displayed as ch 4.x (up to 4 sub channels)
Sorry if this is confusing, it's only because it is.  Scary part is it makes sense to me. 
To put it briefly the TV doesn't know where ch4 got parked on the new band so on initial setup it scans the whole frequency band. Neat thing is they can re-assign a channel and the info is transmitted to your TV automatically. Your guide will load channels that you can't tune in though. (mine does) Where I'm at it shows channels from Gainsville, FL. because some people are in an over lap area and can pick up both cities. I can't and my TV doesn't know it's actual location. (Sat receivers ask for your zip code)
BTW the antenna your using a lot of people think the "front" is the arrow pattern (the longer VHF rods) it's actually the stubby UHF three prong portion. (short rods) The two offshoots are actually reflectors to the center section. (don't ask, some guy with a lot more grey matter than me designed it) |
Ronbo,
Thanks for the explanation. It helps make sense why my set-top digital tuner(s) originally tune to a specific UHF frequency and thereafter flips the displayed channel info to read traditional channel numbers for known local networks. At first I thought it odd but apparently they all do it according to plan.
My simple understanding of VHF parallel reflector and director antenna elements are that the reflectors are spaced 180 degrees out of phase, and behind, with the chosen wavelength and the director elements are in phase ahead of the main dipole. Or is it visa-versa? The "tapered" length variation supposedly broadens the band response, I think. A V-shaped UHF array is even more mind boggling.
Quote:
Originally Posted by Ron61
The original TV antennas were designed with the longer rods to pick up more of the old analog signals than the short ones that feed the TV would. That way you got better reception and not so many ghosts. When we had antennas here I figured out all the frequencies, we only could receive 6 stations and cut aluminum rods to the exact length of each frequencies wave length. Worked great. No standing wave refractions at all.
Ron
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I'd like to see that, Ron. I used to wonder if I couldn't place tuned lengths of twin-lead dipoles stapled on my ceiling to match specific local channels. The idea was to paint over them to obscure their presence but my wife wouldn't let me try it in HER house.
I wasn't sure how I could mix and match the various 300 ohm feeds.
We used to have only have three VHF channels, PBS, NBC and CBS for years. Somewhere in the '80's we got two UHF channels, ABC and FOX. I don't think the UHF have as much broadcast range, but I think the VHF is good up to about 75 miles. Lucky for me I live close to all.
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