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What I spent my Saturday afternoon doing...


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13 replies to this topic

#1 OFFLINE   Mark Lamutt

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Posted 02 October 2004 - 06:05 PM

I put up a 2nd OTA antenna this afternoon to get rid of a splitter that was in the line. Nothing like the never-ending battle of picking up digital signals that are broadcast with just slightly more power than a 100 watt lightbulb... (and no, I'm not kidding or exaggerating...)

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#2 OFFLINE   BFG

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Posted 02 October 2004 - 06:10 PM

are you using something like two of these? http://www.radioshac...duct_id=15-2160

I feel your OTA pain, the stations around me broadcast around 1000kw or less... Which is about 1/5 the power they use for analog. Digital stations, just don't wanna pay their power bill :(

#3 OFFLINE   Mark Lamutt

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Posted 02 October 2004 - 07:27 PM

Yup, those are them. At this point, I think I'd kill for 1000kW of power. I'm 2.3 miles from the worst station in Denver. They are broadcasting at less than 3kW of power from the top of their 6 story building in downtown Denver.
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#4 OFFLINE   boylehome

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Posted 02 October 2004 - 08:47 PM

I put up a 2nd OTA antenna this afternoon to get rid of a splitter that was in the line. Nothing like the never-ending battle of picking up digital signals that are broadcast with just slightly more power than a 100 watt lightbulb... (and no, I'm not kidding or exaggerating...)

Mark, It looks like you have more than one antenna positioned in a different direction, did this cause any signal loss? On mine, when I used a splitter the loss dropped about 20 points on the mid power signals and I lost all of the low power signals. I used my 6000 to measure the signal strength. How do you have the antennas in-line? Currently, I'm dependant on one deep fringe antenna with an amplifier and rotor. I would love to be able to have a separate antenna for each transmission location. The low power stations are about 65 miles away.

#5 OFFLINE   Mark Lamutt

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Posted 02 October 2004 - 11:47 PM

The top yagi runs to my 921 and my HTPC Hipix card through a splitter. The bottom yagi and the gold double bowtie run into an A-B switch, and from the switch directly to my office Hipix card. I'm just about dead even between our standard Denver broadcast tower location (Lookout Mountain) where our WB and Fox digital channels are, and downtown Denver where ABC, CBS, NBC and PBS digital channels are coming from.

I'm not getting any signal loss with the 3 antennas positioned like that (or at least no noticible signal loss), but nothing's being combined together either.
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#6 OFFLINE   boylehome

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Posted 03 October 2004 - 07:39 AM

I'm not getting any signal loss with the 3 antennas positioned like that (or at least no noticible signal loss), but nothing's being combined together either.

Have you checked the signal of the channels solely with the one antenna and one cable? If you experience no noticeable signal loss with your configuration, then this may be the way to go? I wonder if they make an amplifier that has two or more inputs and one or more outputs? Thinking if they did, then I could use one RG6 for each antenna to maintain the highest db gain, provide a boost and branch to more than one TV/Monitor. Ever hear of doing something like that?

#7 OFFLINE   Mark Lamutt

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Posted 03 October 2004 - 11:00 AM

I'm not sure what you mean with the check - I haven't checked signal strength with just one of the antennas mounted on the mast with one cable straight through to one receiver. But, as none of the cables coming from the antennas are combined together at any point, I know I'm not getting any loss from that. I do get the standard 3.5dB loss from the one splitter I have in line, and I probably get a miniscule loss from the A-B switch on the other line.

I don't know of an amp like that for RF cable. I've seen them for composite and svideo, but not of RF. If one is made, it'd be pretty expensive I'd bet.
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#8 OFFLINE   kenglish

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Posted 03 October 2004 - 03:59 PM

Actually, 1/5 of the analog power is about what it takes to get equivalent coverage on the digital.

BTW, if you are using two antennas in a stacked configuration, and have baluns (transformers) on the antennas.....connect BOTH baluns twin-lead wires to one of the antennas and see if the signal drops significantly. If so, swap leads on the second balun and try again. You want them to ADD, making more signal. Mark the leads, then connect them to the two antennas.

Most baluns are randomly wired, so you have to do this to see which leads are (both) positive or negative. Also, be sure the antennas are both "right side up", by matching the way the elements are connected. (I did this backwards one time. Felt so stupid, I didn't do it again, though!)

#9 OFFLINE   boylehome

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Posted 03 October 2004 - 04:50 PM

Actually, 1/5 of the analog power is about what it takes to get equivalent coverage on the digital.

BTW, if you are using two antennas in a stacked configuration, and have baluns (transformers) on the antennas.....connect BOTH baluns twin-lead wires to one of the antennas and see if the signal drops significantly. If so, swap leads on the second balun and try again. You want them to ADD, making more signal. Mark the leads, then connect them to the two antennas.

Most baluns are randomly wired, so you have to do this to see which leads are (both) positive or negative. Also, be sure the antennas are both "right side up", by matching the way the elements are connected. (I did this backwards one time. Felt so stupid, I didn't do it again, though!)

Concerning the baluns, are you referring to 300 ohm leads as the twin leads? If so, I didn't know that it would make a difference in how they were connected. Would it be better to take a 300 ohm cable and hook it to one end to one antenna then the other end at the antenna with the balun then have the 75 ohm cable output from there? And also, is there a required distance between the antenna's? I do know that it you use two or more antenna's but aim them in different directions, they will lose db, but if they are aiming in the same direction, db should increase. Because of the distance and low amount of power of some local OTA's and the fact that they are located in different geographic locations, I've been unable to have more than one antenna work. I do think that if there were separate leads from each antenna and if the leads went into an amplifier with isolated inputs, I could maintain the distant low power signals. I will give the balun twin lead hook-up the test to see if there is a difference.

#10 OFFLINE   Mark Lamutt

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Posted 03 October 2004 - 10:10 PM

I'm not using my antennas in a stacked configuration. They separately provide signal to different receivers. I don't really understand the stacked configuration anyways. Don't the antennas have to be an exact distance apart depending on what channel frequency your're trying to get? And connected together somehow with an "exact" length of cable?
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#11 OFFLINE   boylehome

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Posted 04 October 2004 - 06:23 PM

I'm not using my antennas in a stacked configuration. They separately provide signal to different receivers. I don't really understand the stacked configuration anyways. Don't the antennas have to be an exact distance apart depending on what channel frequency your're trying to get? And connected together somehow with an "exact" length of cable?

I'm no expert here but my research suggests that the antennas must be separated according to the wavelength for S:W:R. there is a mathematical equation for the distance. I don't know where it is. The exact length of cable my be helpful but as a rule, "as short as possible" is advised. Not having the equation, the best thing to do is aim the two or more antennas with at least an equal distance apart, check your signal. try moving each of them equally apart and see if there is signal improvement. Continue the process until it starts to degrade then move them back. Slow but sure process. The cable or 300 ohm wire needs to be twisted 360 about every so many feet?

#12 OFFLINE   Mark Lamutt

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Posted 05 October 2004 - 08:43 AM

I spent a little time last night modifying my setup here. I took out the double bowtie antenna from between the yagis, and put another 18 inches of space between the yagis. I went from 4.5 between them to 6 feet between them. And then I put the double bowtie antenna on the bottom at roof level. After making this adjustment, I now have a full 10 points more signal strength on my weakest channel. After a little research yesterday, I determined that spaced at 4.5 feet, the antennas were interfering with each other. At 6 feet, things seem to be better.
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#13 OFFLINE   boylehome

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Posted 06 October 2004 - 07:20 AM

I spent a little time last night modifying my setup here. I took out the double bowtie antenna from between the yagis, and put another 18 inches of space between the yagis. I went from 4.5 between them to 6 feet between them. And then I put the double bowtie antenna on the bottom at roof level. After making this adjustment, I now have a full 10 points more signal strength on my weakest channel. After a little research yesterday, I determined that spaced at 4.5 feet, the antennas were interfering with each other. At 6 feet, things seem to be better.

Good going Mark. If you come up with an idea that will help me (as stated in previous posts) let me know. I would like to be rotorless.

#14 OFFLINE   Mark Lamutt

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Posted 06 October 2004 - 07:53 AM

I think your best bet if you want to lose the rotor would be to put up another deep fringe anteanna or two on different masts pointed in the different directions, and then use an A/B/C switch (however many you need) between them. You'd definitely be better off going that route than trying to combine them to one cable coming in.

There are a ton of threads about anteannas, stacking and the like over at AVSForum in the archives. That's where I found that I had mine too close together initially.
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