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KC2ESD
06-28-2006, 01:34 AM
I going to build a new multi-band dipole for 40-20-10 Meters.
What is a better way to feed the antenna, Coax Cable or Ladder Line? I have a MFJ-941E Tuner with a Built in 4:1 balum and a connection for Ladder line as well as Coax PL-259 connectors. There are Hams in my area that swear by ladder line. I want the best for my new antenna project.
73 de Rick KC2ESD

W6ECE
06-28-2006, 01:43 AM
Ladder line

WA4NMS
06-28-2006, 01:50 AM
Multi-band antennas are almost always better with ladder line. Keeping in mind the tuner only affects the line between the tuner and the radio. The line between the tuner and the antenna will be unchanged and possibly extremely high VSWR, with attendent losses if coax is used. Ladder line losses are much lower given identical mismatches. Coax is generally best used with tuned antennas.

Dave Marshall
WA4NMS

VK2TIL
06-28-2006, 02:27 AM
In another topic recently, WA6OML told us about this page of LB Cebik's site;

http://www.cebik.com/edz/aledz.html

A good guide to what you propose.

Thanks, OML.

N4AUD
06-28-2006, 02:41 AM
Ladder line.

Coax works well in some situations, balanced feedlines in others, as stated above.

VK4XJB
06-28-2006, 02:53 AM
Ladder line.

The trick question is would you want to buy some 450 ohm window line or make some ladder line yourself? 2 lengths of wire, some spacers every 2 feet or so and you have your own low loss transmission line.

KC2ESD
06-28-2006, 03:19 AM
It looks like so far the vote for Ladder Line is Unanimous.
I'll order some soon.
Rick KC2ESD
Any one who wants to chime in go ahead.

K3STX
06-28-2006, 03:24 AM
I'll be the devil's advocate and say "coax". I have a ladder-line antenna (and a tuner), and it is great. The only problems come when you have to get the ladder-line into your house!! It is best to keep it away from metal objects (at least a couple of inches), so there goes squishing it under my storm door or casement window. Other problems with ladder line too (no point going on, as I say I love my ladder line antenna).

A resonant antenna fed with coax is a dream. No tuner needed, you can bury the stuff in the ground, squish it under storm door, tie it to your metal ductwork, no problems.

For a SINGLE wire antenna, use ladderline and a tuner. If you can make a fan-dipole, coax is great (I have one of them too, you can never have too many antennas).

paul

AI4EP
06-28-2006, 03:37 AM
http://www.qrz.com/iB_html/non-cgi/emoticons/tounge.gif

Ok folks...what are the BAD points to LADDERLINE ?

http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

WA9SVD
06-28-2006, 06:08 AM
Quote[/b] (ai4ep @ June 27 2006,20:37)]http://www.qrz.com/iB_html/non-cgi/emoticons/tounge.gif

Ok folks...what are the BAD points to LADDERLINE ?

http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif
Well, as already pointed out, one BIG problem can be getting the feedline INTO the shack! It really does NOT like being in close proximity to metal objects, and that includes aluminum siding, aluminum rain gutters (vinly gutters usually don't pose much problem) and of course, metal window frames. Not insurmountable problems, but requiring a bit of careful planning.

Also, the connections at the antenna elements can be a bit more frail that coax connections, unless properly supported.

WZ4I
06-28-2006, 10:19 AM
Ladder line.

W5JO
06-28-2006, 11:02 AM
If you decide to use ladder line, then take a look at antennas made by W7FG. The wires are continous and it is true ladder line. The window line will deteriorate in the sunlight over the years leading to changes in impedance.

Since the wire is continous, you don't have trouble soldering the line to the antenna and that makes for a much stronger installation. This will stand up to flexing in the wind which soldered connection won't as well.


I, personally, don't like the built in baluns in tuners. The can get hot and be lossy, depending on the match to the line and antenna. This can become an issue if you use an amplifier. If you want to do that, you can put the balun at the antenna and use coax to the rig from the antenna.

WA2ZDY
06-28-2006, 11:25 AM
W5JO is correct - the baluns in most tuners aren't the best. #They're like any other "parts of something else;" they're the minimum necessary so the maker can say "and it has THAT too."

Use an outboard balun and you can solve the problem of getting the ladder line into the shack too.

Radioworks (yes, I love mine) has a current balun (very important: #don't get a voltage balun) they call the "Remote Balun." #Use a length of no more than about 10 feet of #GOOD coax - 9913, RG213, LMR400 - from the coax output of your tuner to the outboard balun. #Use the coax to get through whatever opening you choose to the outside. #And run the open wire/ladder line from the balun to the antenna.

You'll still be trying to tune the coax which is never a happy occassion. #But it'll only be a very short length of good quality coax and thus will be worth the trade-off for the convenience of using coax to get outside.

Why open wire? #Coax gets ugly when there's a mismatch between it and the load (antenna.) #It becomes more lossy and radiates. #As long as you have a good match up there, like K3STX notes, coax is great. #Once you tune away from the frequency that antenna is cut for, you start to cause yourself trouble.

Open wire works much better with wild mismatches at the feedpoint. #This is why you can use a tuner efficiently in the shack with open wire. #You still have the mismatch at the feedpoint, but it doesn't cause the problems it does with coax.

The ideal arrangement? #Having coax to the tuner and having the tuner at the feedpoint. #If you have an autotuner, that might be practical. #I've done that. #But for #most it's not convenient, so the other set up is second best.

Good luck.

W8JI
06-28-2006, 12:03 PM
There are a few common misconceptions being propagated in this thread.

First, SWR does not cause or cure cable radiation. Feedline radiation is caused by common mode currents, and that is a balance issue. It is not an SWR issue.

Connect a coaxial cable directly to a perfectly balanced antenna like a dipole, and the cable will radiate even with a 1:1 SWR. Change the SWR to 100:1 with no changes in anything else and the cable will radiate exactly the same amount.

Second, ladder line is not always as good as we might hear or assume. There are cases where it has less loss than a good coaxial line, and cases where ladder line has more loss. The real low loss open wire line was constructed quite a bit differently than the W7FG and window ladder lines. It generally had large bare conductors with a minimum of dielectric materials.

The W7FG line has dielectric covering the wires, that's not a good thing. It has wider spacing than window lines, that's not always good news either.

I'm sure either type of "ladder line" would be a much better choice overall in a single wire element dipole than trying to use conventional coax, but there are other alternatives that would have less loss and fewer problems. Fan dipoles and trap dipoles with well-constructed traps come to mind.

If you don't mind paying for and using a tuner (especially one with a good balun), ladder line is a very good choice. It isn't the end-all showstopper, however. It is just a good choice if you have a good tuner and balun, or unless you are willing to use other complex matching schemes with the ladder line.

By the way, use the lowest impedance (closest spaced) ladder line with the heaviest conductors you can find. Matching will be easier.

73 Tom

W5DXP
06-28-2006, 12:45 PM
Quote[/b] (w8ji @ June 28 2006,06:03)]Connect a coaxial cable directly to a perfectly balanced antenna like a dipole, and the cable will radiate even with a 1:1 SWR. Change the SWR to 100:1 with no changes in anything else and the cable will radiate exactly the same amount.
How do you change the SWR from 1:1 to 100:1 without changing anything else? http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

W5DXP
06-28-2006, 01:00 PM
Quote[/b] (KC2ESD @ June 27 2006,19:34)]I going to build a new multi-band dipole for 40-20-10 Meters. What is a better way to feed the antenna, Coax Cable or Ladder Line?
You didn't say if it would be a fan dipole or single wire dipole. For a fan dipole, I would use coax. For a single wire dipole I would use ladder-line.

Here's a rule of thumb for smoothing the SWR's across the bands. EZNEC says that you may encounter feedpoint impedances between 50 ohms on 40m and 5000 ohms on 20m. SQRT(50*5000) = 500 ohms. Ladder-line with a Z0 of 500 ohms will limit the maximum SWR. In other words, the SWR for the 1/2WL dipole and for the one wavelength dipole will be approximately the same at 10:1, perfectly acceptable for ladder-line. And if you want to run that dipole without a tuner, use N*1/2WL of ladder line on 40m and add or subtract 1/4WL of ladder-line for 20m operation.

W0LPQ
06-28-2006, 01:12 PM
I would opt for a fan dipole (not di-pole or di pole) and use coax. Given the bands you want, you also get the option of using teh 40M section for 15M.

I have one fan for 40/17 and another for 40/20. They are notin the same location either. One is out back and is driven by either the SR-150 or TS-50. The one in front is driven by either the 1000MP or TR-4C. I also have a full size 40M vertial out back with coax relay switching between antennas and radios.

In both cases, I have a choke balun (8-10 turns of RG-213) at the feed point of each antenna.

No problems with RF in either location.

As has been said, if it is a single wire, then the choice is obvious. Ladder line.

Bill, W0LPQ

K3UD
06-28-2006, 01:42 PM
Over the years I have tried ladder line and 300 ohm twinlead for various wire antennas and have never had what I would consider good luck with them. My largest problem was RF in the shack and interference to phones and TVs in the house. Using coax cable on resonant half wave dipoles or quarter wave half slopers I do not get the RF and the interference to other electronics in the house.

Now this is probably a quirk unique to my situation, but I have not been able to beat it using ladder line or twin lead, but it all goes away when I use coax. Getting the ladder line into the house also presented problems as my feedlines come in through a hole in the in the bottom aluminum part of the storm window and then through a hole in the bottom wood part of the house window.

I once condidered cuttiing a 2-3 inch hole through the outside and inside wall directly into the shack and putting a PCV pipe section through hole and running the feedlines through it, avoiding the contact with the aluminum. My wife talked me out of it though.

Ladder and 300 ohm twinlead seems to work for many hams in their installations. It has always been a bit tricky for me in my installation. YMMV

73
George
K3UD

W8ZNX
06-28-2006, 05:01 PM
hello

for wire antennas like dipoles, big loops
open wire

love the stuff, easy to use
works great
costs less than coax
best multi band wire antennas
ive ever had were all fed with open wire

open wire does not cause rf in the shack

i run from qrp to well over 600 watts
using open wire feed
antenna tuner is a old Johnson Match Box

have not had one bit of rf in the shack

shack is in basement
wood frame house

more than one place the feed line
comes with in 8 in of metal objects

feed line comes right in thrugh the wall
in to shack
runs for 15 feet over head in side the shack

mac

W5DXP
06-28-2006, 05:59 PM
Quote[/b] (K3UD @ June 28 2006,07:42)]Over the years I have tried ladder line and 300 ohm twinlead for various wire antennas and have never had what I would consider good luck with them.
That's because the result usually doesn't depend upon luck but upon knowledge, experience, and hard work. In particular, to avoid Murphey's law, it is necessary to understand the impedance transforming properties of transmission lines with reflections.

W5DXP
06-28-2006, 06:03 PM
Quote[/b] (w8znx @ June 28 2006,11:01)]i run from qrp to well over 600 watts using open wire feed antenna tuner is a old Johnson Match Box have not had one bit of rf in the shack
It's pretty difficult for common-mode current to get past that link-coupling in the Johnson Match Box. http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

W5JO
06-28-2006, 08:44 PM
Quote[/b] (w8ji @ June 27 2006,23:03)]The W7FG line has dielectric covering the wires, that's not a good thing. It has wider spacing than window lines, that's not always good news either.

73 Tom
Tom the W7FG stuff does not have dielectric on the wire. It is bare copper weld (I think) wire with high quality spacers about every two feet or so. It is a single wire from the feed end up to the specified amount of feeder, then splits into one leg of the dipole. The other leg is just like it.

KA5S
06-28-2006, 09:27 PM
Quote[/b] (KC2ESD @ June 27 2006,21:34)]I going to build a new multi-band dipole for 40-20-10 Meters.
What is a better way to feed the antenna, Coax Cable or Ladder Line? I have a MFJ-941E Tuner with a Built in 4:1 balum and a connection for Ladder line as well as Coax PL-259 connectors. There are Hams in my area that swear by ladder line. I want the best for my new antenna project.
73 de Rick KC2ESD
"Better" covers a lot of ground.

Ladder-line and window-line tolerate high SWR's better than coax, due to having much less dielectric loss. Since they contain less copper -- now quite expensive - they may cost less than coax (but figure in the cost of baluns or tuners). As they are neither of them shielded, you may get more noise on receive if they pass near a source of noise, and more RF in the shack if they are unbalanced by passing near conductive objects.

You can use ladder line without a tuner if you use a balun that matches the line you have. If you are feeding an antenna with a 50 ohm coaxial feedpoint you'll need two such baluns, one for each end. Or use a tuner on one end and whatever you need on the other end.

You will already have been clued in on the problems routing parallel-wire line. Coax is much less critical. However, if there's 200 feet to the antenna, compare the cost of new cable!

You can get decent multiband operation from an 88 foot dipole center fed with "open-wire" line. For this you'll need to use the tuner and its balun, which should work fine.

Have fun!

Cortland
KA5S

KL7AJ
06-28-2006, 10:43 PM
Use ladder line for transmitting and coax for receiving. When you transmit, ladder line gived the electrons something to hang on to when they climb up to the antenna. During receive they can just slide down the inside of the coax. If your rig is higher than your antenna, then of course you'd do just the reverse.

Eric

K3UD
06-28-2006, 11:11 PM
Quote[/b] (w5dxp @ June 28 2006,12:59)]
Quote[/b] (K3UD @ June 28 2006,07:42)]Over the years I have tried ladder line and 300 ohm twinlead for various wire antennas and have never had what I would consider good luck with them.
That's because the result usually doesn't depend upon luck but upon knowledge, experience, and hard work. In particular, to avoid Murphey's law, it is necessary to understand the impedance transforming properties of transmission lines with reflections.
I guess you are right about needing to have the experience and the knowledge.

Having tried ladder line and 300 ohm twinlead off an on for over 40 years I have to admit that if I felt that it was not working out I just terminated the project and went back to coax fed antennas. I do have an old Johnson 275 watt Match Box and have used it when attempting to use ladder line in the 60s and 70s.

Might give it another try later this summer just to see if I can tame the beast and make it work. Time to crack open ye olde antenna handbook.

73
George
K3UD

W5DXP
06-28-2006, 11:20 PM
Quote[/b] (K3UD @ June 28 2006,17:11)]Having tried ladder line and 300 ohm twinlead off an on for over 40 years I have to admit that if I felt that it was not working out I just terminated the project and went back to coax fed antennas. I do have an old Johnson 275 watt Match Box and have used it when attempting to use ladder line in the 60s and 70s.
The Johnson Match Box doesn't have a wide enough tuning range to match everything that ladder-line can throw at it. But by changing the length of the ladder-line, a compromise impedance can usually be reached that works very well. It's just a matter of solving the problems.

W8JI
06-29-2006, 12:54 AM
Quote[/b] (W5JO @ June 28 2006,13:44)]
Quote[/b] (w8ji @ June 27 2006,23:03)]The W7FG line has dielectric covering the wires, that's not a good thing. It has wider spacing than window lines, that's not always good news either.

73 Tom
Tom the W7FG stuff does not have dielectric on the wire. #It is bare copper weld (I think) wire with high quality spacers about every two feet or so. #It is a single wire from the feed end up to the specified amount of feeder, then splits into one leg of the dipole. #The other leg is just like it.
No kidding! A guy brought an antenna to field day he called a W7EG antenna, and the feedline and antenna wire was insulated soft wire!

Are there different models, or was he mistaken?

73 Tom

W8JI
06-29-2006, 12:59 AM
Quote[/b] (W5JO @ June 28 2006,13:44)]
Quote[/b] (w8ji @ June 27 2006,23:03)]The W7FG line has dielectric covering the wires, that's not a good thing. It has wider spacing than window lines, that's not always good news either.

73 Tom
Tom the W7FG stuff does not have dielectric on the wire. #It is bare copper weld (I think) wire with high quality spacers about every two feet or so. #It is a single wire from the feed end up to the specified amount of feeder, then splits into one leg of the dipole. #The other leg is just like it.
I just looked at the web site and it looks exactly like the antenna the local ham had at field day.

As I recall his was a black insulated flexible stranded #16 gauge wire with PVC spreaders, and that's what the photo's at the w7fg site look like.

Look here:
Ladder line (http://www.w7fg.net/ladder/runtower.jpg)

73 Tom

W8JI
06-29-2006, 01:03 AM
Quote[/b] (w5dxp @ June 28 2006,16:20)]
Quote[/b] (K3UD @ June 28 2006,17:11)]Having tried ladder line and 300 ohm twinlead off an on for over 40 years I have to admit that if I felt that it was not working out I just terminated the project and went back to coax fed antennas. I do have an old Johnson 275 watt Match Box and have used it when attempting to use ladder line in the 60s and 70s.
The Johnson Match Box doesn't have a wide enough tuning range to match everything that ladder-line can throw at it. But by changing the length of the ladder-line, a compromise impedance can usually be reached that works very well. It's just a matter of solving the problems.
The easiest thing to do is get inside the matchbox and take a turn or two off the link.

That will extend the matching range greatly.

All of my Matchboxes have two taps on the link, one for low Q one for high Q.

73 Tom

N0WVA
06-29-2006, 02:41 AM
By "multiband dipole" do you mean seperate dipoles cut for different bands connected to the same feedline?

Personally, I like the ladderline with folded dipoles. They are broad banded and will match the ladder line well. I would not use ladder line with regular dipoles. Id use coax for that.

Some may ignore the mismatch at the antenna when using ladderline. Im more of the opinion that it may as well be done right so there is maximum power transfer and minimal rf on the line. Using folded dipoles gets us closer to that.

KC2ESD
06-29-2006, 05:35 AM
Quote[/b] ]You didn't say if it would be a fan dipole or single wire dipole. For a fan dipole, I would use coax. For a single wire dipole I would use ladder-line.

A Fan Dipole.


Quote[/b] ]By "multiband dipole" do you mean seperate dipoles cut for different bands connected to the same feedline? Yes.

KA0GKT
06-29-2006, 05:56 AM
The great thing about folded dipoles is that they are more broadband than a single wire flat-top; the drawback is that they don't accept power at even harmonics, but work pretty well on odd order harmonics. A folded dipole where both elements are the same gauge wire will have a resonant impedance of about 300-Ohms, so it makes for a pretty good match to window line; however that really isn't the point for using a balanced feed line, as has been mentioned elsewhere in this thread.

Neither Coaxial Cable nor balanced feed line is necessarily better than the other in all situations. For unbalanced antennas (verticals, for instance) an unbalanced feed is usually best. For balanced antennas, a balanced feed is best; this can be in the form of ladder line or coaxial line and a Balun (BALanced to UNbalanced). For a single antenna to cover as broad of a range of frequencies as possible, the largest flat-top with a balanced line feed and a good transmatch is still a good answer. The antenna doesn't need to be pruned to resonance and a non-resonant doublet will get you on the air with little fuss.

One other advantage to ladder line is that, unlike coaxial cable, it can easily be home brewed, if you are so inclined. I made a couple of hundred feet once using film reels from 120 and 220 (2 1/4") roll film. I was working at the time for a wedding photographer and had an "IN" at the local pro lab. I bought a barrel of the reels for the same price the recycler offered.

Some question mismatch losses when using ladder line, however, these are minimal, especially when compared to losses using coaxial cable in a similar situation. I have posted this link in other ladder line threads, and for simplicity's sake, I'll post it once again in this thread.


"The Lure of Ladder Line"; December, 1999 QST Magazine (http://www.arrl.org/tis/info/pdf/9312070.pdf)


73 DE KAGKT/7

--Steve

W5DXP
06-29-2006, 12:26 PM
Quote[/b] (w8ji @ June 28 2006,18:59)]As I recall his was a black insulated flexible stranded #16 gauge wire with PVC spreaders, and that's what the photo's at the w7fg site look like.
I bought 200 feet of the w7fg open-wire line. It seems to be ordinary #16 stranded insulated 600v wire with 3.25" spacers made out of irrigation tubing. What would be your estimate for the dielectric losses? The rats ate the insulation and ate through the copper wire before I could get it installed. http://www.qrz.com/iB_html/non-cgi/emoticons/sad.gif

Also, as far as losses are concerned, does a solid copper transmission line have any advantage over stranded or vice versa?

WA9SVD
06-29-2006, 09:50 PM
If you are talking about seperate dipoles cut for each band, and connected to the same feedpoint, then I'd go with coax. We thought you were putting up a single dipole to use on multiple bands!

You will run into some interaction, so the exact lengths will have to be a bit of "trial and error" with some trimming in order, as with any dipole, except you will have more than one dipole to trim...

Just make sure you have good, solid connections to the individual dipole elements; I'd suggest stainless bolts, lock washers, and nuts with ring terminals on the wires, crimped AND soldered for connection at the feed point. Unless you do that, don't even THINK you can add dipoles for other frequencies ar a later time! If you just solder it all together at the feedpoint, you will regret it sooner or later.
And be sure to provide some sort of strain relief for the feedline, so wind/ice/birds don't cause it to break.

VK4XJB
06-29-2006, 09:52 PM
Quote[/b] (KC2ESD @ June 29 2006,15:35)]A Fan Dipole.
With a fan dipole I would say coax will be easier. My view is fan dipole - coax and a single dipole for multiband use - ladder line.

W2VW
06-30-2006, 03:07 AM
Both feedlines have major drawbacks. Coax feed can cause backaches and an upset xyl due to all the up and down it will take to prune the antenna for lowest SWRsss's. Ladder or openwire line could end up straining the brain trying to digest ac theory.

W5DXP
06-30-2006, 01:10 PM
Quote[/b] (w2vw @ June 29 2006,21:07)]Both feedlines have major drawbacks. Coax feed can cause backaches and an upset xyl due to all the up and down it will take to prune the antenna for lowest SWRsss's. Ladder or openwire line could end up straining the brain trying to digest ac theory.
Virtually anyone can download the *free demo version* of EZNEC and configure a dipole with a transmission line. Not much RF theory to learn and EZNEC does all the straining. Now what was your excuse again? http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

http://www.eznec.com

AG3Y
06-30-2006, 10:41 PM
I experienced a very easy thing with significant results, today. I have been struggling with an open wire fed antenna for some time, now. I had been feeding it with a 4:1 balun, and just could NOT get it to act right on the lower bands it was designed for.

To make a long story short, I stuck a 1:1 balun on it, and matching it to 40 and 80 became a cinch !

Bottom line, get a couple of different baluns, and if one doesn't work, for whatever reason ( balanced line length in my case ) the other one quite possibly will !

73, Jim

AG3Y
06-30-2006, 10:42 PM
"SWRsss" http://www.qrz.com/iB_html/non-cgi/emoticons/rock.gif http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif

W2VW
06-30-2006, 11:50 PM
Quote[/b] (AG3Y @ June 30 2006,15:42)]"SWRsss" http://www.qrz.com/iB_html/non-cgi/emoticons/rock.gif http://www.qrz.com/iB_html/non-cgi/emoticons/biggrin.gif
Yup. I plan to use the term enough so that it will be considered normal.
73'ssss.

WA2ZDY
07-01-2006, 09:57 PM
Jim, the discussion on the DX Engineering site gets into why a 1:1 is a better choice in most cases than a 4:1.

http://www.dxengineering.com/pdf/Choosing%20the%20Correct%20Balun.pdf

Go to the last quarter of page 2. There is more detailed discussion further into the document but I haven't time right now to look for it.

I never had trouble with my 4:1 current balun from RadioWorks, but the info on DX Engineering does make sense and I'd trust it if there are troubles like you had. And as you found, the solution was the correct one.

WA7KKP
07-03-2006, 09:04 PM
Ladder line / open-wire feed line

Coax lines have to have a reasonable match (less than 2:1), and that rarely happens the first time out on dipoles. You have to nip and tuck the wires to get them to work right, and you need a seperate feedline for each dipole, unless you feed them in parallel.

Ladder line can tolerate high SWR with less loss, and one feedline can go to ONE dipole, whose length is not critical. By using an antenna tuner such as the Matchbox, you simply tune the complex impedance at the transmitter end to 50 ohms needed by the transmitter/rig. No trimming, and as long as you have a half-wave in the air on the lowest band you intend to use, you'll get out just fine.

Gary wA7KKP

K8JD
07-04-2006, 04:31 AM
COAX, YES for a multi wire, fan dipole, also try one of the 1:1 baluns in the center, the kind that also can provide a support for the weight of the ant and feedline at the center. I use the MFJ balun for two of my dipoles. works great.

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