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Thread: OTA Antenna

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    Hi guys, back at this one. I have reviewed and noticed Terryl mentions amplified splitter, and Jvvh mentioned pre amp, what do you think is better? I did change the cable from Antenna to the house, from the house in, I did not bother, to much work. I also changed the Balun, (channel master brand). I think there was mention I might have a pre amp, but I do not, the box near my antenna was the Motor housing. So which should I get? If I got a pre amp, can I add it maybe ten feet down from Antenna for easy access? When I first changed the Balun, I received a crazy amount of channels, but as time went on, it seems I am back to square one and getting half about 20 something.

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    A pre-amp should be as close to antenna as possible. A power splitter would be used in the house as you have to run coax from each output to your end point--one does not want to do that at the antenna even if you have a weather-tight enclosure.

    The drop in channels is a bit of a puzzle. A balun would not go bad, so, I would think that you had good propagation conditions for a while and then they went poor--that is a sign that you are far from the transmitters, have an obstruction in the path and at times the weather permits better propagation but at times restricts propagation.

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    ok thanks. Yeah it was odd, I had like 40 channels, then next day pretty much gone. Is a pre-amp better than a power splitter? which do you think will work better? I am right near lake Ontario so I should have very little obstruction.

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    couple other quick questions... should the large section of the antenna face towards where i am aiming antenna or small v section? also you guys suggested power splitter, my splitter right now is outside under wooden eaves, will this work as i assume i need to power it to a electrical outlet? Also why would my motor all of a sudden not work, new issue? lol

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    Weather conditions over a lake can create odd density gradients and density gradients are why radio/TV signals bend as they go through them.
    Motor going out could be lots of things: it is old and rusty and does not have enough lubricant, or a wire could have come off.
    I'm not sure I can picture your antenna from what you are saying, but a "small V section" is likely the UHF part of the antenna and it should point to where you want to get signal. The largest elements of an antenna go to the back and away from where you want signa
    I suspect your power splitter came with instructions--you should follow them.

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    Thanks Jvvh5897, I will check the motor, and lubricate it, my Antenna faces the right way based on what you have said. and I will go out and get a pre amp and try.

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    I agree with some of what JVVH has said, however in many many many years of field repairs to antenna systems I find that mounting the pre-amp where it can be easily and/or safely reached is the best setup, if the mast is 30 feet tall off the roof and the pre-amp is right below the antenna then you will have to drop the whole mast to replace it, and they do go bad.

    A short 10, 20 or 30 foot piece of good RG-6 quad coax will not drop the signals all that much, the pre-amp will work just as good.

    However using one with a shot over a large body of water will/can cause problems, as JVVH mentioned the signals can and will bounce and that causes a out of phase signal drop or total loss of signal, this because the bounced signal is 180 degrees out of phase from the main signal, if you use a pre-amp you will also amplify the bounced signal.

    The normal TV antenna like you have now has a beam angle and beamwidth to it, this if looking from the top looks like a stretched out tear drop, (pointy end at the front of the antenna) it will look the same from the side, it is this beamwidth and angle that is also picking up the bounced signals, one thing that has been done is to tilt the antenna up (or down) to keep the bounced signals out of the main lobe of the received beamwidth, you will need to know how wide the receiver beamwidth is for the antenna you have, then with a little trigonometry you can calculate the amount of tilt you may need on the antenna to still get the main signal and try to reject the bounced signal.

    This may prove difficult depending on the terrain and where the lake/bay/river/ocean is located from you.

    To help you understand the beamwidth here is an application PDF file for a UHF antenna, the 91XG from Antennas Direct is a very good high gain UHF antenna, as you can see the first picture is looking at the forward gain and receive beamwidth of the antenna, (looking down at the antenna) the second one is it's receive beamwidth angle looking at it from the side, you can see the angles that the signals could be picked up at.

    On this antenna the half power beamwidth for TV channel 14 is 51 degrees, if you tipped the antenna up about 12 degrees you can drop the bounced signal severely, how much ???? it all depends on the antenna.


    Code:
    https://www.antennasdirect.com/cmss_files/attachmentlibrary/91XG-TDS.pdf
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    Thanks Terryl, great info. but nit grasping the learning curve. So are you now saying, for get the pre-amp?

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    Hi guys back at this one. I just bought a CM-700-1 Tuner and a CM-3414 Distribution Amp. I got a good deal so I bought them. Is there any benefit to this tuner vs running antenna cable, direct to tv? Anyways my questions is, I bought the amp to experiment with better signal quality, but now I might have a dilemma. I have one cable coming down from antenna to a two-way splitter, branching off to two tv's at opposite ends of the house. Ideally, I would like to remove splitter and replace it with the amp. However because the splitter is outside, this will be a issue to connect the amp, as I need a power supply. I have nothing outside or nearby, So can I keep the splitter and connect the distribution amp after the splitter in the line.

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    You can, but the best place to put an amp is as close to the antenna as possible. The splitter with decrease signal to both port's output and an amp should be before that splitter. You can buy cheap in-line amps that you run the power to them on the coax line itself, the power will run through the splitter if you have to do it that way, but it is better to get the signal into the building before splitting it. An amplifier can cause issues if you don't use it correctly (mostly an issue when you have strong, near-by transmitters).

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    This was a distribution amp. I actually did a trial run, just plugging in the power supply outside, and found no improvement. I removed the splitter and replaced with the Cm-3414 Channel Master. Do you think I need a pre-amp as well? I seen no or very little gain.

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    By-and-large an amp should be used to boost signal to compensate for the looses in the coax and splitters between antenna and TV. If your coax run is short or if your losses at the TV channels you get is low with your coax or if you have strong signals to start with, then little or no amplification is needed and if you have amplification then it just causes your TV's AGC circuit to reduce the signal level (assuming that you don't overdrive the front end).

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    Hi guys, thanks for continuing to respond to this post. I recently, now have bought a new channel master CM-9537 Antenna rotator control unit. I also ran all new 3 conductor rotator wire. The Antenna now rotates again. I also mentioned I added the CM7000-1 converter box, not sure it helps in anyway, but I got the signal and quality on many channels best I can. On many i get 100% quality but signal never much past 50%, would this be a indicator my signals are weak? Most channels are like this American and Canadian. Would this be an indicator I do need a pre-amp?

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    I've played with a number of converter boxes and the Q and S indicators are really no indication of much of anything--they are built to help non-tech folks aim their antennas and little more. I have found that early RCA boxes had a "hidden" set of menus that gave SNR readings (and the code could be modified in interesting ways), and early boxes of some others had similar "hidden" diagnostic screens. I don't know about the CM boxes though. If you peek inside and report on the processor then maybe I could tell you more--there is often a TTL level serial port connector of some sort in the converter boxes that let you figure out stuff. The MStar processor's code usually have a serial monitor program running that lets you do lots of stuff over serial port like dump memory to usb port. You find rebranded MStar boxes from lots of folks lately (like the last RCA box)---so if it has usb recoding feature, odds are it is MStar based.

    OH--just went to google and checked on cm7000 and found that that is an old box--I remember it. It has jtag port inside and STM micro processor. It is not a bad old box but had it's issues where we tried to use them (as they got older they had trouble booting up was the biggest one). I did use the jtag port to dump the flash and looked around a little.

    Those MStar boxes are a little better with marginal signals--but all the boxes have similar digital cliff so if you are getting the channels OK then a better box will not get you more, just give you newer features (maybe not better features).
    Last edited by jvvh5897; 07-05-2017 at 04:50 PM.

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    Thanks Jvvh, kind over my head, but good knowledge. I spent enough climbing the tower and running the new cable. lol. So I guess I should not pay attention necessarily to the number it provides. The project is coming along, slowly but surely. do you think I should even use the tuner? Is there any advantage to just hooking direct to tv? I have a 4 years LG tv.

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