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View Full Version : Really Long Coax Run



Gerowen
06-27-2014, 10:38 PM
I have a friend who is wanting to set up a CB radio in his house. Mine is on my back porch, as depicted in the video I posted in the other topic, but he lives in a valley that is really narrow, and in my experience helping set up antennas for other people, narrow valleys like that hamper you a lot. My mom set one up in her front yard in a valley about that size, and she just barely makes it to me from less than 3 miles away. So in order to get up and over the mountain-sides he wants to run coax up the side of the hill for about 450 feet. Several people around here have gotten some left-over TV cable from the cable company for dirt cheap when they run new lines (big thick stuff about the size of your thumb), and they'll run 50 feet of RG8U into their radio, and 50 feet into the antenna, but they'll put that thick stuff in the middle, and they get good results. The problem is I don't think the cable company has any extra laying around for sale, and since it's just a couple hundred feet instead of a couple thousand like some of the guys who use that hardline, we're thinking of just buying a big 500 foot roll of RG8X or RG8U and rolling out what we need and keeping the rest for spare jumpers, etc. Would RG8X or RG8U be OK to use for a run this long? Would there be any serious loss? RG8X obviously is cheaper, so if it would work alright we'd like to stick with that.

222DBFL
06-28-2014, 01:27 AM
The losses will be high with rg8x over that long a run. IMO, I wouldn't skimp out here. You need good coax for that long a run. And the cable company coax won't work as it's 75ohm coax, not 50ohm coax. You need either ladder line, or something like ldf4-50a. I wouldn't even think to use that long of a run of rg8x. JMO.

Gerowen
06-28-2014, 01:56 AM
Found some for $3.18 a foot, that's crazy expensive, but I agree that for going that length where line loss would become noticeable, it'd be better to get the best you can afford and not worry about it ever again. I might just help him do say 100 feet of RG8U for now, and then save up the money to get something better later. Seems like all of really low loss cables out there cost a pretty penny.

222DBFL
06-28-2014, 03:40 AM
I don't pay for mine as I Find most of what I need at job sites where there is leftover coax. I will look around for ya, no guarantees, but I might be able to find some ldf4, or some lmr 400. Let me look around at work. I am a cell site technician, and every so often I will run across a decommed, site that has coax not being used. I'll see what I can find. God bless and have a great day.

BOOTY MONSTER
06-28-2014, 04:46 PM
i'll second the ladder line ...much less loss than any coax you'll find for that long of a run !

http://www.arrl.org/feed-lines

222DBFL
06-28-2014, 05:54 PM
The bigger the better!! Just don't find 1 5/8" sections that long laying around!! The best I get these days is 60ft pieces of Andrew LMR400 and some 60ft lmr240 with an Andrew n-male connector on one end. That's a great find for me these days!!! Anyway, yes sir some 7/8" or been some LDF4-50A would work. Low loss!! I will look around and see what I find as I have been trouble shooting for sprint lately and there's so many colocation sites it's silly. 4-6 carriers on one tower is common place these days lol. But anyway, coax will be going to the wayside soon for fiber. Less work and much faster data. It's all about data these days!!

BOOTY MONSTER
06-28-2014, 10:46 PM
fiber optic coax will be awesome !!!! :300 (254):
with no copper/aluminum even direct lightning strikes on the antenna will have no effect on equipment in the house/shack . :love:

222DBFL
06-29-2014, 02:18 AM
One day booty monster, it's coming, maybe 5-10 years the way we do things. But it surely will decrease weight, time, and money!! And the speed. All for the good.

BOOTY MONSTER
06-29-2014, 12:17 PM
being serious again ..... since FOC is't electrically conductive it would be a pretty big deal IMO . if it could be made to transmit a electrical current (RF is AC) and keep loss to almost zero it will revolutionize the power transmission from the nation's power grid to electronics constronics to flash lights . no signal/electrical loss and no grounding concerns .... WOW !

222DBFL
06-29-2014, 12:21 PM
It is some near stuff. They are building DAS (distributed antenna systems) in stadiums and hotel natonionwide that the antennas are light being feed by fiber. Cool stuff , they turn RF into light through duplexers and a major fiber network. Helped build the largest one in the US at the super dome in LA. Wish I would have taken photos!!!!

Tallman
07-03-2014, 04:31 PM
Maybe you should just rig up a repeater for yourself. transmit with low power to your tower of high power!

BOOTY MONSTER
07-03-2014, 08:59 PM
It is some near stuff. They are building DAS (distributed antenna systems) in stadiums and hotel natonionwide that the antennas are light being feed by fiber. Cool stuff , they turn RF into light through duplexers and a major fiber network. Helped build the largest one in the US at the super dome in LA. Wish I would have taken photos!!!!

pics would be sweet .
soooooo ... the velocity factor of fiber optic coax/feedline should be somewhere between 100 and 99.999 ?

222DBFL
07-03-2014, 09:04 PM
It's fast as light!! Losses are very low, normally under .5db with a fiber tester. This is through the entire system. The technology is here, and there is more to come!! The days of pulling in long coax runs up the tower are now becoming a thing of the past. Good and bad!! Less work in the end, but less time to complete the job as well.

NY714
07-05-2014, 04:15 PM
Times Microwave LMR-400, from MPD DIGITAL Company directly on the web This hobby can get expensive, but you want to do right and only once. Buy in bulk rolls to save money. "It Cost Money To Run With The Best" Sure you can do cheaper but will you get the same results "NO"

mjd420nova
07-10-2014, 02:59 PM
My first thought would be a long wire and balun. Is the hillsides on both sides clear of any other utilities?? If there are no obstructions, some light wire and a bow and arrow would give you coverage. Multiple wires could even be used, only two at a time, to get the coverage that works best. I use this method in the woods and directional arrays are possible. I use very fine wire, but a little heavier would be best for longer exposures.

BOOTY MONSTER
07-10-2014, 04:08 PM
.......he wants to run coax up the side of the hill for about 450 feet. .....

even with lmr-400 that's almost 1 s-unit (4-4 1/2 db) of signal loss on both tx and rx . about 1/3 of your tx power will reach the antenna .... the majority 2/3 of your tx power will be lost in the coax run .

soooo .... spend $500ish and lose contacts for less effort...
or
spend a quarter of that with more install effort for much less loss/more power reaching the antenna keeping most of the systems ERP .

222DBFL
07-11-2014, 12:03 AM
He needs some LDF4-50a or similar. The larger the better. 7/8" coax would work as well. But at 450 ft. You are taking about a bit of money. Not going to be cheap that's for sure!!

hotrod
07-22-2014, 02:23 PM
get a starduster m400 mount it as high as possible next to home , and use lmr 400 coax . this antenna will
help him get out of valley better and no need for 450 feet of coax thats just insane