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#11
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A DTV antenna
Dave Platt wrote:
Unfortunatly, I can't mount an outdoor antenna. I rent, and the landlord won't allow it. Isn't there a federal law allowing TV antennas? Or did you sign a personal contract agreeing not to install a TV antenna? The OTARD rule (to which you're referring) allows installation of an over-the-air TV antenna, but it only applies if the antenna is installed in an area which is exclusively for the tenant's use. People who rent houses are usually able to take advantage of it. Apartment dwellers often can't, because they aren't renting the whole building and thus don't have "exclusive use" rights to the roof or exterior. But if you have a terrace or a porch, you may install a receiving antenna for broadcast or satellite on that porch. |
#12
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A DTV antenna
Ian Jackson wrote:
In message , Richard Clark writes When the band shift comes, rabbit ears could work quite well. Don't take the plunge into elaborate designs until you have some basis of comparison is all I am suggesting. I would start with sticking a screwdriver in the TV antenna socket. While a properly designed and constructed DTV antenna, mounted in the right place, will undoubtedly work well, some of the homebrew designs you find on the internet are probably even less efficient than a screwdriver. I have seen some very clever antennas on the internet. More clever than the BS this newsgroup is top-heavy with. |
#13
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A DTV antenna
Dave Platt wrote:
The OTARD rule (to which you're referring) allows installation of an over-the-air TV antenna, but it only applies if the antenna is installed in an area which is exclusively for the tenant's use. People who rent houses are usually able to take advantage of it. Apartment dwellers often can't, because they aren't renting the whole building and thus don't have "exclusive use" rights to the roof or exterior. However, they do have exclusive rights to their balcony or patio so that's something to consider. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
#14
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A DTV antenna
On 25 Apr 2009 06:33:45 +0100, Gordon wrote:
This seems to be the only news group devoted to the topic of antennas. (and the origins of the universe). So maybe you guys can help me with this. Cosmology is often easier to understand than the antenna designs. I have been experimenting with fabricating a decent indoor DTV antenna. Please define "decent". You know, the numbers. How big? (max allowed length, width, height) How much bandwidth (VHF, UHF, or both?) Minimum (average) gain? Mounting limitations? Omni or directional? Rotator? I'm also partial to NEC2 models of creative designs. They often show problems that are not obvious until after the antenna is built. If you're going to design your own, spend the time building a model. I have tried several things. You seem to have done your homework. Also see: http://www.hdtvprimer.com/ANTENNAS/comparing.html Some are indoor antennas, which should give you a clue as to what to expect. What I have now is two bowties spaced about 7 inches apart on a wood dowel. A peanut butter jar with rocks in it makes up the base. 2 element yagi like design? It seems to give pretty good performance. It could be better. But I am wondering about a few things. 1) Right now all the digital transmissions are in the UHF band. but in 6 weeks, three stations will move back to their VHF assignments in the VHF high band. How well can I expect my antenna to work in that frequency band? Dunno. I haven't seen any dimensions. Plug the current design into an NEC model and see what comes out at VHF frequencies. My guess is that it will be worse than hideous. You would do better with adjustable rabbit ears. 2) I have not trimmed or dressed the twin lead from the bowties. I understand that twin-lead can act as antennas. So what is the best way to manage the twinlead? Cut it back? I noticed that when i laid the leads together, in an attempt to make a neat assembly, I got signal cancelation. Lose the twin lead. The problem with balance line is that any mechanical imbalance (i.e. proximity to walls, objects, people, etc) will unbalance the line, causing some radiation. Such radiation shows up as loss, something you can barely tolerate with such a minimal antenna. If your design is setup for a 300 ohm match, install a balun and run 75 ohm RG-6/u coax instead. 3) Any suggestions to improve this design? Improve how? More gain? More bandwidth? Smaller? Numbers please. 4) Any suggestions for alternitive DIY designs? Yes, but you may find them rather unconventional. I once built a log periodic antenna on a sheet of plywood, using #14 AWG house wire and two parallel wires for the transmission line. Elements were arranged on both sides of the plywood and secured with a staple gun. This was for a ladyfriend, who was stuck with severe limitations on outside antenna installations. I hung it from the ceiling, which was the only place suitable for the monstrosity. 4-6dBi gain from 60 to 800MHz (no channel 2). Where were a few ghosts, but it worked much better than the rabbit ears and UHF loop it replaced. However, it only lasted about a month. The landlord found out and demanded its removal while muttering something about attracting flying saucers and alien visitors. Oh well. Another TV antenna I built took advantage of the chicken wire buried under the stucco outside of the house. The chicken wire acted as the antenna reflector, which was conveniently arranged in the right direction. The driven elements were 4ea phased bow-tie dipoles, hidden behind a decorative wood grating. It didn't work as well as I predicted, but good enough to get decent OTA TV reception. If you have a suitable window facing the right direction, you can do something with aluminum foil tape. I use aluminum duct tape cut down to size for this purpose. For electrical connections, copper stained glass tape soldered to the coax cable. Any antenna with horizontal polarization will work. You won't get much gain, but the outside window location will somewhat compensate for the lack of gain by offering a less cluttered line of sight to the TV xmitter. Anyway, use your imagination, but also run the numbers and do a model. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#15
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A DTV antenna
On Apr 26, 12:17*am, (Dave Platt) wrote:
Unfortunatly, I can't mount an outdoor antenna. *I rent, and the landlord won't allow it. Isn't there a federal law allowing TV antennas? Or did you sign a personal contract agreeing not to install a TV antenna? The OTARD rule (to which you're referring) allows installation of an over-the-air TV antenna, but it only applies if the antenna is installed in an area which is exclusively for the tenant's use. People who rent houses are usually able to take advantage of it. Apartment dwellers often can't, because they aren't renting the whole building and thus don't have "exclusive use" rights to the roof or exterior. -- Dave Platt * * * * * * * * * * * * * * * * * AE6EO Friends of Jade Warrior home page: *http://www.radagast.org/jade-warrior * I do _not_ wish to receive unsolicited commercial email, and I will * * *boycott any company which has the gall to send me such ads! Unless they have a balcony which is their "own space". |
#16
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A DTV antenna
On Sun, 26 Apr 2009 16:54:12 -0700, Jeff Liebermann
wrote: What I have now is two bowties spaced about 7 inches apart on a wood dowel. A peanut butter jar with rocks in it makes up the base. Like this? http://www.hdtvprimer.com/ANTENNAS/DoubleBow.html -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#17
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A DTV antenna
Dave Platt wrote:
Unfortunatly, I can't mount an outdoor antenna. I rent, and the landlord won't allow it. Isn't there a federal law allowing TV antennas? Or did you sign a personal contract agreeing not to install a TV antenna? The OTARD rule (to which you're referring) allows installation of an over-the-air TV antenna, but it only applies if the antenna is installed in an area which is exclusively for the tenant's use. People who rent houses are usually able to take advantage of it. Apartment dwellers often can't, because they aren't renting the whole building and thus don't have "exclusive use" rights to the roof or exterior. It's considerably more subtle than that, since there are large commercial interests at play (unlike for ham antennas).. Go to the FCC OTARD page and get the real scoop. http://www.fcc.gov/mb/facts/otard.html As a practical matter, the courts/adminstrative law judges have held that the landlord's control does not cover, for instance, the air space outside your window, so if you can mount the antenna within the window's dimensions(either inside or outside), you're good to go. It is ok for the landlord to prohibit, say, attaching to the wall outside, though. Whether the window frame itself is "under your control" is another question. |
#18
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A DTV antenna
Jeff Liebermann wrote in
: On Sun, 26 Apr 2009 16:54:12 -0700, Jeff Liebermann wrote: What I have now is two bowties spaced about 7 inches apart on a wood dowel. A peanut butter jar with rocks in it makes up the base. Like this? http://www.hdtvprimer.com/ANTENNAS/DoubleBow.html Sort of. At least that's the right configuration. What I did was to go out and buy a pair of bowties from Radio Shack. Then I got a dowel at Ace Hardware. I clipped the bowties 7" apart (measured on center). to the dowel. The bowties came with about 12" or so of twin-lead attached. I ran these to a balun and then through a short length of coax to the DTV converter. I don't have a reflector, but one could be used to improve directionality. |
#19
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A DTV antenna
Jeff Liebermann wrote in
: On 25 Apr 2009 06:33:45 +0100, Gordon wrote: This seems to be the only news group devoted to the topic of antennas. (and the origins of the universe). So maybe you guys can help me with this. Cosmology is often easier to understand than the antenna designs. I have been experimenting with fabricating a decent indoor DTV antenna. Please define "decent". You know, the numbers. Decent is subjective. When I first hooked up the converter box I used the rabbit ears. They didn't work worth a darn. Signal strength (according to the OSD indicator) was 40 at best. THe picture and sound were constantly breaking up. I then hooked up a bowtie and got better reception, but only barely. That's when i got the idea for the double bowtie. Now my worst signal strength is 40 and my best is 75. Still could use some improvement, but picture quality is good. How big? (max allowed length, width, height) That's the thing. I don't have room for a ginormus antenna. How much bandwidth (VHF, UHF, or both?) Right now, UHF 27 to 48. After the change over, add VHF 8, 10, and 12. Minimum (average) gain? Mounting limitations? Prefer indoor not outdoor. A high ceiling makes that mounting arangement unusable. Although I could hang a flat antenna on the wall around the corner from the TV. Omni or directional? Rotator? All the stations are located within a 7 degree cluster, due east from my location. Directional is good. No rotor needed. I'm also partial to NEC2 models of creative designs. They often show problems that are not obvious until after the antenna is built. If you're going to design your own, spend the time building a model. I have tried several things. You seem to have done your homework. Also see: http://www.hdtvprimer.com/ANTENNAS/comparing.html Some are indoor antennas, which should give you a clue as to what to expect. What I have now is two bowties spaced about 7 inches apart on a wood dowel. A peanut butter jar with rocks in it makes up the base. 2 element yagi like design? It seems to give pretty good performance. It could be better. But I am wondering about a few things. 1) Right now all the digital transmissions are in the UHF band. but in 6 weeks, three stations will move back to their VHF assignments in the VHF high band. How well can I expect my antenna to work in that frequency band? Dunno. I haven't seen any dimensions. Plug the current design into an NEC model and see what comes out at VHF frequencies. My guess is that it will be worse than hideous. You would do better with adjustable rabbit ears. 2) I have not trimmed or dressed the twin lead from the bowties. I understand that twin-lead can act as antennas. So what is the best way to manage the twinlead? Cut it back? I noticed that when i laid the leads together, in an attempt to make a neat assembly, I got signal cancelation. Lose the twin lead. The problem with balance line is that any mechanical imbalance (i.e. proximity to walls, objects, people, etc) will unbalance the line, causing some radiation. Such radiation shows up as loss, something you can barely tolerate with such a minimal antenna. If your design is setup for a 300 ohm match, install a balun and run 75 ohm RG-6/u coax instead. 3) Any suggestions to improve this design? Improve how? More gain? More bandwidth? Smaller? Numbers please. 4) Any suggestions for alternitive DIY designs? Yes, but you may find them rather unconventional. I once built a log periodic antenna on a sheet of plywood, using #14 AWG house wire and two parallel wires for the transmission line. Elements were arranged on both sides of the plywood and secured with a staple gun. This was for a ladyfriend, who was stuck with severe limitations on outside antenna installations. I hung it from the ceiling, which was the only place suitable for the monstrosity. 4-6dBi gain from 60 to 800MHz (no channel 2). Where were a few ghosts, but it worked much better than the rabbit ears and UHF loop it replaced. However, it only lasted about a month. The landlord found out and demanded its removal while muttering something about attracting flying saucers and alien visitors. Oh well. Another TV antenna I built took advantage of the chicken wire buried under the stucco outside of the house. The chicken wire acted as the antenna reflector, which was conveniently arranged in the right direction. The driven elements were 4ea phased bow-tie dipoles, hidden behind a decorative wood grating. It didn't work as well as I predicted, but good enough to get decent OTA TV reception. If you have a suitable window facing the right direction, you can do something with aluminum foil tape. I use aluminum duct tape cut down to size for this purpose. For electrical connections, copper stained glass tape soldered to the coax cable. Any antenna with horizontal polarization will work. You won't get much gain, but the outside window location will somewhat compensate for the lack of gain by offering a less cluttered line of sight to the TV xmitter. Anyway, use your imagination, but also run the numbers and do a model. |
#20
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A DTV antenna
Ian Jackson wrote in
: I would start with sticking a screwdriver in the TV antenna socket. While a properly designed and constructed DTV antenna, mounted in the right place, will undoubtedly work well, some of the homebrew designs you find on the internet are probably even less efficient than a screwdriver. You mean, like the beer can antenna?? Sorry, I don't have a link. |
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