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Old 03-15-2019, 11:42 AM
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Antenna issues with Agile Modulator Help please

I currently have a BT 40-550 set to CH10 and I made a dipole antenna cut to 14.4 inches each side. (I know the 40-550 is weak, I have ordered a 60-550 but it has not arrived) I think that even the 40 should work better then it does. I have tried rabbit ears, an outdoor antenna (Just standing next to my bench) and the dipole attached to the basement ceiling. In the same room it works well, it is watchable one room over. If I go up to the main floor, it is all but washed out. What I want to know is how the dipole should be mounted? Horizontal or Vertical? I would think Horizontal but I am not getting good results. Where in the house is best? I followed the instruction in the posted video on how to make the dipole, I think I did it correctly. I am not over modulating (The lights are off) In my area according to TV fool, CH7 is still in use, CH9 is in use but takes an outdoor antenna to get it. 11,12, and 5 are red and required an amplified outdoor antenna pointed at the correct direction. So aside from CH7 and to be safe CH9, the rest are ok to use. I picked 10 because it seems to work the best for me. Look for help to make this work better because I still want to be able to use the BT40 even when I get the BT60, basically making sure I have this thing setup as good as possible. Thank you
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Old 03-15-2019, 06:57 PM
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On Channel 9 I have an AM40 throwing signal at least 3 houses down the block at max power.

I've got horizontal polarization, I followed shango66's youtube vid except for not having a SWR meter when I made it (I have access to a network analyzer (which makes a SWR meter look like a cheap toy) at work so I may remake my antennas soon). One thing to note Shango used an equation that probably came from ham radio and probably assumed 50ohm (or maybe 300) transmission line instead of the 75ohm the BT uses...He cut the antenna length down to tune it to the line impedance.....If I recall my antennas elective correctly to tune a dipole to TX line impedance you need to change it's length by a percentage...That percentage holds over frequency so calculate what percent he trimmed, and remove the same percent of your length.

Also what your house is made of and where your ant is within it will affect reception...Ductwork, tile, masonry, stone, pipes, many layers of floor, metal furniture, people (yes when people move multipath varies) all can attenuate or reflect your signal...If you didn't see your house built from a frame avoiding that stuff is pure guess work...It does seem like my basement and 2nd floor rigs don't like to talk to each other static free though (despite traveling as much as a block radially).
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Old 03-15-2019, 08:45 PM
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You didn't say what kind of antenna is on your receiver or its orientation. I would put the transmitting dipole horizontal, but then expect to also use a horizontal dipole on the receiver, and have it oriented the same way, that is, if the transmit dipole is oriented east-west, the receive dipole should be also, not north-south. This would be the least loss in an open field; but as Electronic M says, in your house you could have all kinds of reflections and attenuations. If your house has foil-faced insulation in the walls and attic, you may get strong standing waves, in which case both antenna locations can make a difference just by moving their location a quarter wavelength.
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Old 03-15-2019, 10:27 PM
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My house is wood frame with a steel I beam in the middle of the basement running north and south. The BT is in my shop room in the back of the basement, the A/C metal trunk is above part of the ceiling. I am using a Radio Shack 5" color with a single stick antenna, I also have 3 other little hand held tv's with stick or cord antennas. In the other room I have a set of rabbit ears connected to a vcr that is connected to my big sony crt. (This one gets a picture but it is not very clear). If I go up to the main floor in the bedroom (above and just south of the shop) I can watch but it is not very clear. When I got home from work today, I taped the dipole to the wall in my shop (vertical) and it very clear if you are in the same room but the same issue everywhere else. Tomorrow I will change it to horizontal and look into changing the length (I built it based on Shango's video). And I will make sure that the transmitting antenna is pointed the same as the tv's. Seems that if you guys can get 3 houses from the antenna to work, maybe something is wrong with the BT? I guess I will be able to rule that out once I get the new one. (Next week)
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Old 03-15-2019, 10:49 PM
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Also BTs output level varies with channel (Based on 2 AM40s, 1 AM60, and 2 fixed channel BAMz I have). Most are strongest on 7 and worst on 2 (I've never tried UHF)... you might want to try another channel. Low band isn't necessarily best but 4 might be an option.
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Old 03-19-2019, 07:26 PM
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I got my 60-550 today, built a loop antenna for it and it works well. I built the loop so that it would not be directional. Still want to find the best location for the antenna in the house.
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Old 04-28-2019, 10:40 AM
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Hi, I too just started using the AM60, it is working but being very new to this, I'd like to get it working in a non directional manor. Can you elaborate on this loop antenna and what channel you are using? I am currently using a dipole.
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Old 05-02-2019, 07:53 PM
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I cut mine for ch10, I think it is 43 inches. I used solid copper ground wire bent into a circle and soldered an rg6 coax to the ends. They say Ch7 is the best to use but it is in use in my area. I have the antenna mounted horizontally on the ceiling of my basement. It works very well.
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