Originally Posted by thatdonguy7
Howdy all I'm new and don't know if I'm butting in ,in the wrong place. I lost my channel (3, kiem Eureka CA) in the digital switch. They are now 3.1, but still VHF. The digital signal is too weak. As I'm only after one channel I want to try a custom dipole instead of an amp. We are off the grid and any fraction of an amp adds up. I have lots of room, lots of coax, and lots of copper, (solid core, maybe 12G)
Question, if I make say a 12, 25, 50 foot simple "T" dipole could that help? I know their direction, but not the MHz Any thoughts? On that scale would the length be specific for their VHF brodcast? Thanks, Don.
I built my dipole by cutting it to the wavelength of 36, which is in the middle of the band I receive and the most problematic channel. It is basically twinlead taped to a 2nd-story window, and receives high-V and UHF great from 21 miles away. But 3 means a much longer dipole. I am not sure cutting to the wavelength will really buy you that much gain. Plus, a dipole only has about 3 dB of gain at the max, and is not very directional. Here is a little Java calculator to figure out the size:http://www.qsl.net/w4hn/antennaCalc.htm
Channel 3 returns a dipole of 7 ft, 7 and 23/32 inches.
It is unlikely, but possible, I guess, that a station would choose a low-VHF channel for DT, as it is susceptible to impulse noise which could thwart reception. Almost all DT is high-V or UHF, and most of those who were originally allocated low V unfortunately (such as Chicago CBS 2, which was a nightmare to receive on 3) have gone to a better high-V or U channel after 6-12-09. I would check first very closely to be sure that their physical channel is indeed 3 (3.1 may be a virtual channel, a remap from any other physical channel).
Assuming it indeed is channel 3, if distance is your true problem (as yet undetermined), and as you say, you have the room, I would look into this:http://www.tpub.com/neets/book10/42o.htmhttp://kyes.info/antenna/build.html
Which is about rhombic antennae. Large, cheap and easy to build, and very good for DX-ing distant TV signals. All you need is about 300 ft or so square of land (they don't require height or line of sight). They can give 20 dB of gain. About the best antenna you can buy only gives about 12 dB. Slap a Channel Master preamp on the output, and it should pull in anything up to and just past the curvature of the earth. There's a good chance that you may be able to get away without a preamp, though.
If that is your problem (distance/low gain), then a rhombic is just what the doctor ordered. But that might not be your real problem, it might be multipath interference. Directionality is then what you are after. Typically the more gain the more directionality, and vice versa
, but I do not know if this is true of the rhomboids; more research can probably determine that, however. Apparently, increasing the sides of the rhomboid to multiple wavelengths increases directionality, so build it as big as you can.
If a dipole really is the answer, you might find this article about how to build one interesting as well:http://www.tackyliving.com/article.php?id=61