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Discussion Starter · #1 ·
I need help bad. I am on something like my 10th antenna trying to get local HDTV broadcasts about 10 miles away. My house must be made of lead, because NO indoor antenna will pick up the digital signals.


I now am using a Yagi antenna with excellent reception in my garage attic. Some of the weakest channels in the area show up nicely, but only 20% signal unless I use a preamp (then they are 79%)


Problem is, with the preamp, my weakest DTV channels come in nicely at 79% signal, but CBS (which has the strongest DTV transmitter in the area) cuts out with the preamp on. I think it is experiencing 'signal overload' with the preamp on, every 10 seconds or so the signal strength goes from 100% to 0% and lose pic for one second. I also think NBC, (the second strongest signal in the area) is experiencing some overload because it seems the picture pixellates in fast- motion scenes. This pixellation may just be a crappy compression by NBC, so please comment.


I would like to know:


1) Should I buy a signal attenuator and attenuate my signal to lessen the effects of the preamp? If so, should I install the attenuator before the preamp on the antenna, or after the power inserter by the reciever, or in the middle with all of that Direct Current running about?


----- OR --------


2) Should I just ditch the preamp and buy a distribution amplifier to put up by the antenna.


PLEASE GIVE ME HELP I AM AT THE END OF MY ROPE HERE.
 

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Get the RS adjustable attenuater, and see if it helps,put it after the the pre amp
 

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Discussion Starter · #3 ·
I will try that, but you are sure that putting it after the preamp wont hurt the attenuator with all the DC voltage running around?
 

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After the power supply/inserter for the preamp.
 

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Put the attenuator between the Tuner/STB & the Power Supply.


IOW, the attenuator is the first thing connected to the ANT-IN jack on the STB.
 

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Discussion Starter · #6 ·
I put the attenuator between the power injector and the receiver, and I am able to adjust the attenuator to where I still recieve a signal on my weak stations, but the strong stations still are clipping video even though signal meter shows 100 percent.


I am considering putting the attenuator in between the antenna and the preamp to try to attenuate the signal before it gets amplified. I am thinking that whatever noise exists on this strong signal is getting amplified to near the top of the signal window for my reciever. If I could just attenuate that signal, life would be great.
 

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Discussion Starter · #8 ·
yeah, that individual thing is just what i need. Now, if only someone could tell me how to attenuate one or two channels while leaving everything else amplified I would be in perfect shape!


I imagine that in the future when some broadcasters actually start broadcasting at 'full power' for thier digital signals, this may be a common problem.
 

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Discussion Starter · #11 ·
if i unplug the power I cannot recieve stations at all because the power inserter causes a loss of the signal. with the power inserter totally removed from the line, I can recieve the 3 highest signal stations, but cannot get fox.


Another board I am using the person suggests that using a channelmaster preamp would give a lower signal/noise ratio than the radioshack preamp i am using. They also state it might have a higher 'power output' without distorting than the radioshack preamp. I might try this next.


Next thing I will try is using an inline amplifier for 10db gain. The preamp i am using is 26dB gain, and I am excited to try lower gain with inline amp. I will let you know how it works.
 

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Quote:
Originally posted by lisadaveh
Another board I am using the person suggests that using a channelmaster preamp would give a lower signal/noise ratio than the radioshack preamp i am using. They also state it might have a higher 'power output' without distorting than the radioshack preamp.
Absolutely. The Radio Shack amps are not real high quality amps. The channel master 77xx series is fairly resistant to overload and would definitely be worth looking into.
 

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What channels are overloading? What are the actual channels they are broadcasting digital on (not the "n-1" numbers).


What is your ZIP code or city?
 

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Discussion Starter · #14 ·
Just tried every possible combination of antenna angle, 26db preamp, 10db preamp, no preamp, and both preamps with different attenuations, and I am giving up.

I really thought that a digital signal would be easy to lock on with a yagi in the attic of my garage. Two of my friends are able to get thier local stations with indoor antennas. I have tried every indoor antenna, and the silver sensor was close to perfect, but still had dropouts and really had to aim the thing to pick up 2 of my channels (that stunk cuz all 4 of my locals come within 7 degrees of each other.)

I guess my roof must be made of radioactively enhanced radio wave blocking material or something, because I am starting to give up on the whole overload theory, and starting to believe my problem may be reflections from the roof/attic. If i point my antenna 6 degrees less than all of the transmitters, I can get 70% ish signal on all 4 of my stations without a preamp, but they will all drop out every few minutes.

Tomorrow I will get my butt back on the roof and put my antenna back on my chimney. When it was there before, I had PERFECT analog reception (even better than cable tv locals) If i can't get these 4 stations after putting the antenna on the chimney, I will lose my mind. (by the way, i was trying to avoid putting it on the roof because I had many sleepless nights worrying about lightning hitting the thing, I never properly grounded it because it is in the middle of the roof)


FYI: I live in Mishawaka/South Bend IN 46545. I only want to get channels 30, 35, 42 and 58.
 

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You shouldn't need any preamp at all.


A CM 4221 or RS 15-2160 on the roof and aimed at those stations should get 'em all.


And yes, you should ground the coax with a grounding block, where it enters the house. Also ground the antenna mast. Both should be grounded to your home's main electrical power ground.


This won't prevent damage in case of a lightning hit, but it will reduce the attraction of lightning to your antenna, lowering the odds of a direct hit. It prevents wind induced static buildup on the antenna, which if ungrounded, may eventually discharge into your STB, TV, etc. Over time, this can kill sensitive componenets.
 

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Discussion Starter · #16 ·
can i ground the both the coax and the antenna to the little pole in the ground that the cable company put in many years ago. I assume this would be proper ground rod as they use it for my cable internet and such....
 

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Assuming the "little pole" is a suitable ground rod, you may ground both the coax and the antenna mast to it. But you must also run a ground wire from that ground source to the main electrical power ground. This is called "bonding".


Not bonding your grounds to the main power ground can lead to equipment damage from possible voltage potentials between the different ground sources. The risk of equipment failure is very real (speaking from past experience) :(
 

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Discussion Starter · #18 ·
Have put it on the roof. All Stations come in perfect and solid. The breakup of signals every minute or so when it was in the attic must have been multipath problems. Still weird that the solid stations in the attic would become unstable when amplified, but I assume now that the amplifier was making whatever multipath the attic had on these channels much worse.

I am still unable to get a stable signal on fox28 wsjv on the roof. Can't remember if I ever had a stable signal on it in my attic. I have read that this wsjv fox28 is only broadcasting 10kilowatt digital signal, and therefore I may just have a weak signal in the first place. I am writing their engineer tomorrow about it.

Thanks for all of your help. I have learned a very valuable lesson here. Multipath is the enemy of digital transmissions. Even though my analog stuff was fine in the attic, the digital was too sensitive to the mutlipath.


Dave
 
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