sundance-communications.com/forum Forums Wiring - Telecom Carriers - Trunks & Services Cabling Telephones Systems Wiring House with too many TV's and not enough Signal strength.

Hey Hal,

You seem to know a fair bit about this, I've always been curious about something;
Vaximily mentioned in his original post that the drop amp is a 4 way. It has a 3.5, and three 7dB outputs. I too have seen them like this. How can that be? You are right that they go in multiples of 2 way. Those amps have to be 7dB each tap or if it truly does have one 3.5, then it would have one 7 and two 10.5 drops. Am I wrong in thinking this? There is one brand of DA that I tend to use all the time and it's labeled the right way. Actually it says 3.5, 7, and two 11 taps.

Vaximily out of curiousity, I would try unhooking that 2 way splitter that you have in your room. Hook that feed directly up to the modem and do another test. Right now you have a 7dB drop with those two splitters and it would be only a 3.5 with just the one in the basement.

Just a side note, 3dB is half of your power. Think of it this way, if you have 100% and you drop 3dB, you only have 50% power. Split it again, and you have 25% power. Those splitters are rated 3.5 because the circuit in the splitter has some loss (roughly 1dB).

I heard they make splitters that have no drop at all... doesn't seem possible... do these exist?

/edit/
I have also done some other changes that have put me down to Recieved Signal Strength: -10.3dBmV.

I'll let you know what I get when I put the line directly back on the Amp.

[This message has been edited by vaximily (edited September 02, 2005).]

You want to try to get that up closer to the 0dBmV point.

[This message has been edited by twisted pair (edited September 02, 2005).]

Thanks for the tip, I'll fool with it some more on monday, my next day off. Right now I'm sitting in my car a block from my girlfriends house on an open wireless network, just got this new 14" iBook, I love it, so glad I got it instead of a Windows machine!

Twisted Pair you are close. I have worked with a lot of analog audio transmision circuits and there are four things that can cause loss. You are correct that spliting the signal causes a 3DB loss. The second loss is from "Hysteresis". In 600 ohm to 900 ohm transformers it is about 0.5 DB. in hybrid 2wire to 4wire transformers it is 1 DB. The third loss is from impedance mismatch. With a mismatched impedance say a 75 ohm spliter to a 50 ohm coax. The forth is loss in the transmission line. The longer the line the more the loss.

Yeah I kind of know something about this. I had a decent MATV company back in the mid 60's installing off-air antenna systems in houses and multiple dwelling units. Then when cable came to town I did a lot of work for them as a tech doing everything from installs to outside plant installation and maintenance. Pay was lousy so I went into this business and been there ever since.

I've always been curious about something;
Vaximily mentioned in his original post that the drop amp is a 4 way. It has a 3.5, and three 7dB outputs. I too have seen them like this. How can that be? You are right that they go in multiples of 2 way. Those amps have to be 7dB each tap or if it truly does have one 3.5, then it would have one 7 and two 10.5 drops.

I have never seen one like that but then again I haven't checked Radio Shack or something made in China off ebay selling for $15.00. Only way you are going to know for sure is to feed it a signal and use a signal level meter to see what is on each out. I can't see why anybody would purposely make something like that anyway.

Any 4 output drop amp, house amp, home run splitter (or whatever they want to call it) that I have ever seen had the same level on all outputs. Internally it is an amplifier feeding a 4 way splitter so each output would be 7db down. The amplifier usually has a gain of 7db making the whole thing a wash. It just allows you to split four ways without any loss, giving you the same levels on the outputs as on the input. This is probably what you are talking about-I heard they make splitters that have no drop [attenuation] at all...

That said, I never liked to use those. I always used an amplifier with more gain, usually adjustable and hung my own splitters on the output as necessary. That way I could make what I want and even compensate for a low drop level and long cable runs if necessary. But you have to have test equipment to set it up. Too much gain will cause problems just as sure as a low signal level and keep in mind that when thinking about amplifiers you can't make something out of nothing. If the signal is poor or very low an amplifier will only make things worse.

-Hal

Thanks guys, I learned something here too.

Well the comcast guy came out this morning, apparently the plug they had run up to my room was never crimped, so that was making the signal fluctuate so much. Hopefully no more drop offs, he also replaced the splitter that I put in before the drop amp.

His last suggestion before re-running EVERYTHING was to put a splitter at the side of the house directly off the main line, that'd cut out quite a bit of wire because it wouldn't have to run all the way to the center of the house and the back out and up. (The main line comes in at the same place that the line for my room comes out). So if I'm still having trouble I'll give that a shot.