| Author |
Message |
    
Freebird
| | Posted on Friday, August 22, 2003 - 11:30 am: | 
|
i was thinking about putting my i max 2000 up in a big pine tree but from where my radio is to way up in the tree i think im gonna need about 250 maybe 300 feet of coax.will these mess anything up? |
Taz
| | Posted on Friday, August 22, 2003 - 12:44 pm: |
|
no, just run a minimum of lmr 400, I wouldnt even go that small.
Try the biggest stuff you can afford. |
Scrapiron63
| | Posted on Friday, August 22, 2003 - 1:00 pm: |
|
Freebird, if you will be raising the antenna quite a bit, you will gain lots more than the little loss in the extra coax. My tower is next to my little radio shack, I have about a 100 feet of coax from the antenna into the shack. When I switch into the house, I come thur another 150+ feet of coax, and I can tell very little difference in the house or shop. You can't beat height for a CB antenna. Just my opinion. scrapiron |
Twa77
| | Posted on Friday, August 22, 2003 - 1:22 pm: |
|
you will probably need some good low loss coax. 9913 belden may work or else some of that times lmr 400. someone correct me if i'm wrong.
tony
cef 153 |
Taz
| | Posted on Friday, August 22, 2003 - 1:48 pm: |
|
well RG8U wont work, I would even stay away from belden. I would take LMR400, minimum.
I would probably go with LMR600 |
Taz
| | Posted on Friday, August 22, 2003 - 1:53 pm: |
|
According to my calculations,
LMR900 would be more desirable.
http://www.timesmicrowave.com/cgi-bin/calculate.pl
|
Scrapiron63
| | Posted on Friday, August 22, 2003 - 3:59 pm: |
|
I'm using Belden 8214 RG8 super flex,, the 150 ft coming in the house is buried, has been for about 9 years, no problems yet. 8214 has the same loss as 9913, same center conductor, just a little less shield, thats why it's super flex. The reason I used the 8214, the superintendent of the Belden plant about a mile from my house is a friend, and he told it was the best for the money, for my use. And i've been well satisfied with it, the price was right too, ;>). scrapiron |
Freebird
| | Posted on Friday, August 22, 2003 - 4:39 pm: |
|
Scrapiron63 what kinda coax you running?..right now i just have the thin gray coax the mini b by belden.thats what i was gonna use but im dont wanna go by 200 more feet of it if im gonna lose lots of power cause im running 300 feet of the stuff. |
Taz
| | Posted on Friday, August 22, 2003 - 5:15 pm: |
|
Freebird,
9913 at 300 feet will be very lossy.
Frequency = 27MHz
Attenuation(db/100 feet) = 0.642
Average Power (KW) = 3.51
Run Length (FEET) = 300
Total Run Attenuation(dB)= 1.9
TOTAL EFFICIENCY = 64.2%
At that rate with 9913 you loose 46.8 percent of your power.
What a waste, just go with LMR 900 coax, because with that you will lose around, 19% which is very acceptable.
Im not telling you how to spend your money, just dont want you to be dissapointed. |
Znut
| | Posted on Friday, August 22, 2003 - 5:54 pm: |
|
And WOW you will spend your money on LMR 900! I think it's like 8 or 10 dollars/foot. Connectors are about 30 to 50 dollars each. LMR 400 is pretty affordable these days and there is some competition on the cable/connector market for LMR 100, 195, 200, 400, 500.
I like that loss calculator too Taz. |
Scrapiron63
| | Posted on Friday, August 22, 2003 - 7:34 pm: |
|
Freebird, no doubt you need to buy the best coax you can afford. I wouldn't wanna use 300 feet of mini-8 for sure. On my setup, like I said, I can tell very little difference in the radio in the shop than the one in the house although its going thur another 150 feet of coax. If I have a 30% loss, it would hardly show, the reason why, to raise a meter one S unit on the other end it takes from 2 to 4 times the power, some say 2, I have a hygain antenna book that says 4. Using either number, a 30% loss wouldn't amount to but maybe half an S unit. And like so many have told me over the years, they can't tell if I'm in the shop or the house. scrapiron |
Alsworld
| | Posted on Friday, August 22, 2003 - 7:39 pm: |
|
A good low loss coax would be your best bet. You've got Belden, Times as mentioned and also a great coax not mentioned yet is Davis Bury Flex. Low loss, double shielded that may save you some money without compromising quality. http://www.DavisRF.com
It's your call but fortunately at the CB frequencies, the coax is pretty forgiving compared to the loss factor at some of the ham frequencies.
Heliax would be great at that distance but pretty expensive. If it were me (I run a solid 125ft section of Davis RF myself), I would try and get the best "Low Loss" coax I could afford. The longer sections you buy at most dealers who sell these brands, it gets cheaper by the foot length.
Copper may have an answer on where they can get some of this (low loss coax) if you ask customer service.
Alsworld
|
Taz
| | Posted on Friday, August 22, 2003 - 7:47 pm: |
|
Ive forgotten about heliax, I think that it would be your best bet (1/2in) |
de
| | Posted on Friday, August 22, 2003 - 7:49 pm: |
|
TAZ should be a Ham Op....
Taz is correct. 300 feet is a very lossey lenth even for the lower loss coax let alone any higher loss small diameter coax.
ALSO remember that loss works both sides of the street. Coax that has a high loss factor on transmit also has a high loss factor on receive.
HOWEVER if you wish you just might be able to get away with a long wire antenna. Get a hold of the ARRL Antenna Book and look up long wire antennas. You have the potential for some very nice wire antennas. |
Taz
| | Posted on Friday, August 22, 2003 - 8:19 pm: |
|
Thanks DE.
Im studying, I might go take the test for the heck of it.  |
Bigbob
| | Posted on Friday, August 22, 2003 - 9:23 pm: |
|
Something else you might consider,go with your lossy coax,4 watts at radio,2.5 watts at antenna,just about right to drive most rf amps.If you have a tower then this becomes practical,make a weather proof container with baffeled vents on bottom insert klv550,attach to tower,insert a remote switch in extended power cord,adjust amp to your liking and voila instead of losing 46% of your amplified signal you lose a very negligible amount,heck run 600 feet and you still have 450 watts at your antenna.I read a variation of this idea in an old arrl manual,of course it was 2 meters and a whole lot more compact,but I think it would work,just don't key down for extended periods. |
Bullet
| | Posted on Friday, August 22, 2003 - 10:45 pm: |
|
lmr 600,900,and hardline.thats all nice coax and very spendy as well. i got a 100'run of 600 and thats 130 bucks plus about 60 bucks for conectors. not what most people look to do.
why not use twin lead very low loss better than either coax's mentioned and you can run this in very long runs and lose very little. do a little matching and drive on. |
mikefromms
| | Posted on Saturday, August 23, 2003 - 1:09 pm: |
|
I think the additional height will well make up for any line losses. At the 27 mhz I'd go middle of the road meaning 9913 in the shortest run possible and not worry about it. It wouldn't cost an arm and a leg and the loss wouldn't be as great in reality as it might appear on paper.
Now, if this was 144 mhz or above I'd be whistling another tune.
mikefromms |
Bigbob
| | Posted on Saturday, August 23, 2003 - 6:11 pm: |
|
People must think I'm just spoofing,but I really did read about a remote rf amp installation in an arrl handbook and to me it really makes sense,and if I had a tower YOU DARN BETCHA I'd try this out,you don't need a klv550,heck a 100 watt mobile amp would do,a base amp would be harder to install but you wouldn't need two 6-gauge wires 100 feet long running to it.And in the winter you would never overheat the unit. |
Taz
| | Posted on Saturday, August 23, 2003 - 7:54 pm: |
|
MikeFromms,
Keep in mind, your receive will be half of what it used to be, and so will be your ERP at the antenna.
Even though your going so much higher, I would still go with better coax. |
Tech833
| | Posted on Sunday, August 24, 2003 - 12:10 am: |
|
Taz,
Don't tell me you're a believer now!
I passed on something to the younger generation. Wow. |
Taz
| | Posted on Sunday, August 24, 2003 - 1:38 am: |
|
LOL 833 |
Bullet
| | Posted on Sunday, August 24, 2003 - 5:10 am: |
|
there finally looking at those calculators and figuring these things out! |
Bullet
| | Posted on Sunday, August 24, 2003 - 5:12 am: |
|
i know its enuff coax when my wife says so!
hehehe |
Scrapiron63
| | Posted on Sunday, August 24, 2003 - 11:28 am: |
|
Bigbob, I've ran a remote similar to what your talking about for years. I sometimes use an amplifier that's in my shop with the radio in the house, this is thur a 150 foot 'jumper'. When it's noisy at night and I need the amplifier, it's on a timer, generally set to go off about 11:00 pm, several times i've been talking past that time and someone will tell me it's time to go to bed, my timer just went off because my signal dropped to nothing. I should explain that several guys I talk to are 50 to 100 miles away, thats the reason for a little extra power needed. scrapiron |
Scrapiron63
| | Posted on Sunday, August 24, 2003 - 12:03 pm: |
|
Hey guys, we all know we need to use the best coax and equipment feasible, but we need to understand what we're reading. The posts saying your losing half your receive and tx between RG8 and the other choices are not exactly right, I don't believe. Taz check your math in your post above, you have a 46.8% power loss for the RG8, try 35.8%,I believe that will add up to 100%.
So the RG8 has 35.8% loss, the LMR900 19% loss, the difference would be 16.8%, thats how much more loss you would have between the two. What does that mean on 'getting out' power. Well if your radio is doing 5 watts, with the RG8 you would get 3.21 watts to the antenna, with the LMR900 you would get 4.05 watts to the antenna. That's less that a watt difference, which would hardly be noticed on the other end, and I doubt if any receive difference would be noticed. Remember, it takes 2-4 times the power to raise that signal 1 s-unit. Ok, does my math cipher rite. Like Mike said above, the differences would not be as great as they seem from the figures. scrapiron |
bruce
| | Posted on Sunday, August 24, 2003 - 12:59 pm: |
|
Scrap isn't the point of max lengh when P(loss) =P(in)? |
Bigbob
| | Posted on Sunday, August 24, 2003 - 4:34 pm: |
|
bruce when you get to that extreme wouldn't it be more feasible to have a stick by your shack to tx to a repeater on top of your tower connected to the beam,then you get away from line losses. |
Taz
| | Posted on Sunday, August 24, 2003 - 6:57 pm: |
|
Scrapiron, read my post again. I stated 9913, not rg8/u.
Pretty decent difference between 9913 and generic rg8/u.
9913 is better than the regular rg/8 stuff, so rg/8 would be even less scrap.
Keep in mind all that lost wattage will go into the air as spurious emmisions, and that seems like a waste of money to me, plus it can bother the neighbors too. |
Scrapiron63
| | Posted on Sunday, August 24, 2003 - 7:28 pm: |
|
Taz, 9913 and 8214 like I use, and several others are grouped under RG-8, at least they are under Belden's specs. Thats really what I meant when I said RG-8, I was talking about the 9913 specs you had posted. And your right, anything you can keep in the coax is better, its just according to what you can afford, and if the difference is worth it. scrapiron |
Bullet
| | Posted on Monday, August 25, 2003 - 2:04 am: |
|
so are you guy's telling me that 1000 foot spool of rg58u ive got with conectors at both ends un spooled just enuff to get to the antenna and to the radio is not the way to do things?
i stay so confussed.......
hehe |
Znut
| | Posted on Monday, August 25, 2003 - 3:19 pm: |
|
I beg your pardon Taz. The energy lost in the coax is not manifested as "spurious emissions" my freind. As you do know, energy is not lost, just changed in some way. When electrical resistance is encountered in a circuit the electric energy is simply changed to heat. It may not be enough to feel but run some wattage through a piece of rg316 and you will feel it get hot. |
Bigbob
| | Posted on Monday, August 25, 2003 - 6:09 pm: |
|
Bullet,sounds like the mother of all chokes whether coiled or not. |
applejack
| | Posted on Monday, August 25, 2003 - 11:21 pm: |
|
well hey what about "ladder line"? i know a guy in virginia that lived on BIG A mountain and ran that stuff way up through fields and woods to a ground plane, and talked all over. |
bruce
| | Posted on Tuesday, August 26, 2003 - 8:30 pm: |
|
apple jack ever seen 300 ohm TV TWINLINE? well ladder line is almost the same thing. It is low loss but also in the 400 ohm inp range so some tricky matching would be in order but yes it would work on cb would it be worth your time i doubt it. |
Bigbob
| | Posted on Wednesday, August 27, 2003 - 11:23 pm: |
|
An 8 to 1 balun,or a coax T,quarter wave trap on one leg and a 4 to 1 balun on the other,and I don't know what I'm talking about,lol.hehehe. |
Bullet
| | Posted on Thursday, August 28, 2003 - 12:50 am: |
|
bigbob,(last post)
lol thats what ive always said man im glad someone else finnally see's it as well.
Taz, if your buying id love two 120ft runs of LMR1700 with N conectors please. this will go nicely on my next beam and tower when its done. |
Bullet
| | Posted on Thursday, August 28, 2003 - 12:56 am: |
|
how much coax is to much?
when it starts spewing out of the window of your house its time to stop!
i run enuff to get from point A to B with enuff slack to move my equipment from one wall to the next in the house and enuff for a rain loop. and thats enuff. |
|
