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coiling coax
- Thread starter The Jerk
- Start date
W
W9WD
Guest
I've seen it mentioned about making 3 coils about 12" diameter at the antenna.
Seems like if it made a difference going one way it would make a difference going the other.
Another mystery
Seems like if it made a difference going one way it would make a difference going the other.
Another mystery
W
W9WD
Guest
Try doing a google search for "Coiling Coax" There's all sorts of interesting stuff. Mostly what I read seemed to suggest that unless it was very tightly coiled (like 4") it wouldn't matter. Seems the reason for doing it is to keep the RF from coming back down the outside of the coax from the antenna, which would seem to indicate that there's a problem with the antenna in the first place
I just coiled up a bunch (didn't want to cut my 100' piece) but I made the coils about 3-4' in diameter and leaned it against the house
I just coiled up a bunch (didn't want to cut my 100' piece) but I made the coils about 3-4' in diameter and leaned it against the house
Coiling coax doesn't harm the coax unless it's coiled too tightly. How tightly can you coil coax? Only way I know to say it is until you have to use any appreciable force in making the coil. Doesn't really tell you much, huh? Or, you might see what size the core is on the roll that coax came on. Another not too likely thingy, right? Oh well. A fairly good 'guestimate' is about a foot or so for average coax. If you're talking about 9913, or some really stiff coax, make that coil as large as you can. You can uncurl stuff like 9913 or hard line, but you ain't never going to get all the kinks out of it, make it easy on yourself.
A coaxial choke affects what's on the outside of the coax, not what's on the inside. And it does that in 'both' directions, to/from the antenna. So if you happen to have common mode currents (CMCs) on your feed line they aren't a bad thing to have. They affect things 'after' the choke, not 'before' the choke. That 'before' and 'after' thing depends on where that CMC originates, at the antenna, or at the transmitter. Which basically means put that choke as close to the antenna's feed point, or the output of the radio/amplifier/whatever as you can.
Chokes usually don't hurt anything. If they make a noticeable change, then there's something going on that you need to look into. Got some extra coax you didn't really need and didn't cut off? Coil the stuff up. Shouldn't make any difference. If it does, you got something going on that you need to be aware of. What? Beats me, I have no idea of what your set up is.
- 'Doc
A coaxial choke affects what's on the outside of the coax, not what's on the inside. And it does that in 'both' directions, to/from the antenna. So if you happen to have common mode currents (CMCs) on your feed line they aren't a bad thing to have. They affect things 'after' the choke, not 'before' the choke. That 'before' and 'after' thing depends on where that CMC originates, at the antenna, or at the transmitter. Which basically means put that choke as close to the antenna's feed point, or the output of the radio/amplifier/whatever as you can.
Chokes usually don't hurt anything. If they make a noticeable change, then there's something going on that you need to look into. Got some extra coax you didn't really need and didn't cut off? Coil the stuff up. Shouldn't make any difference. If it does, you got something going on that you need to be aware of. What? Beats me, I have no idea of what your set up is.
- 'Doc
Its in a mobile...DX959, 4-pill (ab-1), and a 102". Swr is 1:1 without power and 1.2:1 with power.
Just looking to see what I can do with the excess, short of cutting.
Just looking to see what I can do with the excess, short of cutting.
It is perfectly ok to coil your coax as long as you do not exceed manufacturers specs. chokes are usually a good thing.
I'm too tired (lazy) to retype this post that I made in another forum so I copied and pasted it here.
" Coax cable is self shielding which means that each turn in a coil cannot "see" any other turn. People claim all the time that you should not coil up excess coax because it will affect your SWR. NOT TRUE! If it does affect your SWR you have other problems causing it such as common mode currents on the coax shield which is very undesireable.Take it from someone that spent 22 years in the commercial AM/FM broadcast business and had many RF installations with excess cable coiled up in equipment racks or ceilings to faciitate future moves of equipment while not going off the air. These installations ranged from the AM broadcast band up to 1.7 gigahertz in frequency range and never, not once, was SWR affected by a coil in the coax cable.
Just a quick note to add. A really tight coil in coax cable may cause the inner conductor to migrate towards the shield and eventually cause a short in the cable. This is especially true of cables that have a foam dielectric and subjected to the heat of the sun. Every coax cable has what is called a minimum bend radius that should be followed when making turns in cable. "
Coiling coax will in no way affect RX/TX performance or SWR .It is better however to use the shortest run as possible from purely a loss point of view.
" Coax cable is self shielding which means that each turn in a coil cannot "see" any other turn. People claim all the time that you should not coil up excess coax because it will affect your SWR. NOT TRUE! If it does affect your SWR you have other problems causing it such as common mode currents on the coax shield which is very undesireable.Take it from someone that spent 22 years in the commercial AM/FM broadcast business and had many RF installations with excess cable coiled up in equipment racks or ceilings to faciitate future moves of equipment while not going off the air. These installations ranged from the AM broadcast band up to 1.7 gigahertz in frequency range and never, not once, was SWR affected by a coil in the coax cable.
Just a quick note to add. A really tight coil in coax cable may cause the inner conductor to migrate towards the shield and eventually cause a short in the cable. This is especially true of cables that have a foam dielectric and subjected to the heat of the sun. Every coax cable has what is called a minimum bend radius that should be followed when making turns in cable. "
Coiling coax will in no way affect RX/TX performance or SWR .It is better however to use the shortest run as possible from purely a loss point of view.
Thanks...
I thought I remembered that being the case, just wanted to verify that coiling would not affect TX/RX.
I would cut it, but I do not have any way to solder new ends...and none of thew shops around here do it correctly, so its not like I could even cut it to length and have the solder the ends on.
The reason I asked is that I will have most of the interior of my truck removed to rewire the amplifier and that's a involved in itself, don't need to be tearing it out again to uncoil everything.
Thanks to all that replied.
I thought I remembered that being the case, just wanted to verify that coiling would not affect TX/RX.
I would cut it, but I do not have any way to solder new ends...and none of thew shops around here do it correctly, so its not like I could even cut it to length and have the solder the ends on.
The reason I asked is that I will have most of the interior of my truck removed to rewire the amplifier and that's a involved in itself, don't need to be tearing it out again to uncoil everything.
Thanks to all that replied.
W
W9WD
Guest
In my case I am moving hopefully sooner rather than later and I don't know what length of coax I will need exactly. So I bought two 100 foot lengths and will cut it when I get to where I'm going.
With my luck, if I cut it now it would be a foot too short