Question: Running coax off the antenna

fletch99

DTVUSA Member
#1
I put an antenna in the attic and am satisfied with the reception. Now I would like to get the coax under the house and then up to to where the connections are needed. I plan on putting a Wingard HDP-269 after the antenna then run off that down through a utility closet to get to the crawl space. Then a three way spliter. My question is should the splitter go in the attic and make three longer runs or is it okay to put the splitter under the house with three shorter runs?
 

IDRick

DTVUSA Member
#2
Welcome to the forums!

It would be easier and cheaper (less cable used) to install the three way splitter below the house. TV signal strength will not be influenced by either install location.

Have fun!

Rick
 

FOX TV

Contributor
#3
I put an antenna in the attic and am satisfied with the reception. Now I would like to get the coax under the house and then up to to where the connections are needed. I plan on putting a Wingard HDP-269 after the antenna then run off that down through a utility closet to get to the crawl space. Then a three way spliter. My question is should the splitter go in the attic and make three longer runs or is it okay to put the splitter under the house with three shorter runs?
Sorry IDRick, I have to disagree on the strength being the same on both setups. All cable has some loss per some measure, usually ohms per feet, or ohms per hundred feet. You would also induce more loss by running 3 cables from the attic, as opposed to running one main cable as far as possible, and then 3 shorter ones closer to their destinations.

It may not be noticeable at the receiver, but there is some loss, and it may only be measurable with some sensitive test equipment, but there is loss in even one foot of coaxial cable. I do agree with your final setup, and I am not trying to criticize, only trying to inform !!
 

IDRick

DTVUSA Member
#4
FoxTV,

Perhaps I do not understand losses. To me, if I have a 100 ft run between the antenna and tv, the expected loss equals the loss for that frequency/100 ft plus the loss going through 1 leg of a three way splitter. It doesn't matter where you insert the splitter, the loss will be the same in this 100 ft run. I do agree that the total loss (summing across the three legs) will be higher with an attic install (3 lines with longer runs) than a below house install. But summing across runs does not accurately portray the loss at the individual receiver. My understanding anyways...

Best,

Rick
 

FOX TV

Contributor
#6
FoxTV,

Perhaps I do not understand losses. To me, if I have a 100 ft run between the antenna and tv, the expected loss equals the loss for that frequency/100 ft plus the loss going through 1 leg of a three way splitter. It doesn't matter where you insert the splitter, the loss will be the same in this 100 ft run. I do agree that the total loss (summing across the three legs) will be higher with an attic install (3 lines with longer runs) than a below house install. But summing across runs does not accurately portray the loss at the individual receiver. My understanding anyways...

Best,

Rick
Ok look at it like this. If he needs 40 feet from his antenna with one cable to the splitter, and then only three short runs of 5 or less feet from the splitter in the basement to the receivers. That is a total of 55 feet of cable used for this setup.

If you were to split it at the antenna and run 3 separate cables of 45 feet each, the total cable length is now 135 feet, plus a short piece from the antenna to the attic mounted splitter.

With this setup, the very same signal level now has to traverse 135 total feet of cable, plus the short jumper at the antenna to feed the receivers. Since all coax has some loss, you are lowering the signal level using this setup because you have tripled the amount of cable used, thus tripling the loss factor for the entire system based only on the loss factor of the cable itself, with all else being the same.

I was not really considering the splitter loss, only the effect of more total cable length in the system.

I don't know that it would make a difference in a lot of situations, but theory says more total cable means more total loss when all else is the same. Did not mean to offend if I did...Sorry !!
 

M4ny

DTVUSA Member
#7
In attic (short run) with 3 long runs to each receiver or in cellar (long run) then 3 shorter runs to each receiver sounds pretty much like a wash to me. Only the OP knows for sure which is shorter I guess.
 
#8
the very same signal level now has to traverse 135 total feet of cable
Bob,

Each terminal signal run in a parallel circuit must be calculated separately as the loss in the three runs are not additive (not a series circuit).

The signal power at the end (of the run) of a N-way splitter followed by a 50' run off each leg will be identical to the signal power if you run a 50' followed by an N-way splitter.

Signal-wise in this example, it is a wash. The preference then should go to the option that offers the best combination of economy (least cable used) and convenience of installation.

run 3 separate cables of 45 feet each, the total cable length is now 135 feet
While the total length of cable used is 135' (not particularly economical), the signal only traverses 45' on each leg. If an "approximate" loss of 6 dB/100' at 700 mHz is assumed, the signal power at the other end of each cable run will be (45/100*6) lower than at the input to each cable run.

As an example, consider the following example including a 3-way splitter (numbers are approximate):

A balanced 3-way splitter should exhibit around 6 dB insertion on each leg relative to the input.

Assume a 700 mHz signal measuring +18 dBm is fed into a 100' length of typical RG6 coax (6 dB loss), then into a 3-way splitter (6 dB loss on each port), then sent down 3 identical 100' runs of RG6 (6 dB loss each) making a total cable length of 200'. In an ideal situation, the signal measured at each of the three terminal runs will be identical at 0 dBm. 18-6-6-6=0

Consider if the same signal were sent directly into the same 3-way splitter. Each output is then fed into a 200' run of RG6. The output of each port of the 3-way splitter will have +12 dBm of signal (6 dB loss per port). After 200' of cable (12 dB loss), the output of each cable will be 0 dBm. 18-6-12=0

It's a wash signal-wise at the end of each cable although one option used a much greater amount of cable.

Disclaimer: All numbers are rounded up to the next typical whole number for the sake of illustration. Actual "numbers" for individual products are not being considered in these examples.

Fletch: Pick whichever is easiest and most economical. Since you're running a pre-amp, you should have adequate signal. Pick whether you want to spend more time rooting around in the attic insulation or crawling around under the house. Both can suck...

PS89
 
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gary350

DTVUSA Member
#9
You are doing it the hard way. Drill a 5/8" diameter hole in the header on the top of the wall where you want the coax wire. Use a tape measure and measure over from the side wall to the location where you want the wire. Go to Lowe's or Home Depot and buy a pop in box and a cable cover. Go to the attic and measure over the same distance you measured down stairs and drill your hole. Cut a hole in the wall for the pop in box. Go to the attic push a wire down inside the wall to the hole near the floor and through the box. Pop the box into the hole attach the cable to the cover and screw on the cover. Now you screw the coax from the TV to the connector on the wall. You can put wire and a box in any room in the house and the wires will be much shorter than running it under the house plus you don't have to crawl under the house in spiders and mud. The good thing about this is there is no wire sticking up through the carpet or wooden floor to get in the way. The box on the wall never gets in the way of steam cleaning carpet of vacuum either. If you put the antenna in the center of the attic you can probably wire any room of the house for TV with only 50 ft or less of coax cable. If you run the wire down a wall, under the house then up it will talk a lot more than 50 ft of coax cable.
 
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FOX TV

Contributor
#10
Bob,

Each terminal signal run in a parallel circuit must be calculated separately as the loss in the three runs are not additive (not a series circuit).

The signal power at the end (of the run) of a N-way splitter followed by a 50' run off each leg will be identical to the signal power if you run a 50' followed by an N-way splitter.

Signal-wise in this example, it is a wash. The preference then should go to the option that offers the best combination of economy (least cable used) and convenience of installation.



While the total length of cable used is 135' (not particularly economical), the signal only traverses 45' on each leg. If an "approximate" loss of 6 dB/100' at 700 mHz is assumed, the signal power at the other end of each cable run will be (45/100*6) lower than at the input to each cable run.

As an example, consider the following example including a 3-way splitter (numbers are approximate):

A balanced 3-way splitter should exhibit around 6 dB insertion on each leg relative to the input.

Assume a 700 mHz signal measuring +18 dBm is fed into a 100' length of typical RG6 coax (6 dB loss), then into a 3-way splitter (6 dB loss on each port), then sent down 3 identical 100' runs of RG6 (6 dB loss each) making a total cable length of 200'. In an ideal situation, the signal measured at each of the three terminal runs will be identical at 0 dBm. 18-6-6-6=0

Consider if the same signal were sent directly into the same 3-way splitter. Each output is then fed into a 200' run of RG6. The output of each port of the 3-way splitter will have +12 dBm of signal (6 dB loss per port). After 200' of cable (12 dB loss), the output of each cable will be 0 dBm. 18-6-12=0

It's a wash signal-wise at the end of each cable although one option used a much greater amount of cable.

Disclaimer: All numbers are rounded up to the next typical whole number for the sake of illustration. Actual "numbers" for individual products are not being considered in these examples.

Fletch: Pick whichever is easiest and most economical. Since you're running a pre-amp, you should have adequate signal. Pick whether you want to spend more time rooting around in the attic insulation or crawling around under the house. Both can suck...

PS89
Who is Bob?
 

fletch99

DTVUSA Member
#11
I'd like to run it down the walls as described above. How do I know that there is not a 2X4 between the studs which would block the cable from coming all the way down ?
 
#12
I'd like to run it down the walls as described above. How do I know that there is not a 2X4 between the studs which would block the cable from coming all the way down ?
You can either use an electronic stud finder to see if it can find fire blocks or you can drill a hole through the top plate and run a fish tape down the stud bay to see if it goes all the way.

Fire blocks typically are installed 4-5' off the floor and are required on exterior walls by most fire codes. Interior walls may or may not have them depending on local codes and building practices.
 

gary350

DTVUSA Member
#13
I'd like to run it down the walls as described above. How do I know that there is not a 2X4 between the studs which would block the cable from coming all the way down ?
Studs are on 16" centers. Drill a hole if you hit something move over 8" and drill another hole. It's not a big deal to drill several holes. The top of the wall has TWO 2x4 boards there it will be like drilling through a 4x4 board.
 

fletch99

DTVUSA Member
#15
Okay. I got two runs down interior walls with no problems. I thought the third would be the same. I drilled thru the top plate and the coax is hitting something about 18 inches or so down. This is an interior wall also but it joins a wall shared with the attached garage. I can only guess that it's a 2x4 between the studs. Do I give up on that run or is there a trick I'm not thinking off. I know I could cut a hole in the wall but that's out right now.

Thanks for the help
 

Orrymain

, Blogger: Orry's Orations
#17
The only thing I can say I know is that each time you use a splitter or make an alternate connection, you do lose strength of signal. I have a crazy set up and I've lost track on how many times cable and tv techs have mentioned that to me. It actually can be visible depending on the connection.
 

fletch99

DTVUSA Member
#18
Finally got the last run in. Got tripped up by studs on 24" centers when the other two were 16" on center. Now a little "repair" work on the walls and I'm done. In hind site it was better to come down the walls than running down to the crawl space and splitting it there. Appreciate the help!
 
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