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Author Topic: Carolina windom 80s - few questions ??  (Read 2143 times)
GM1ZVJ
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Posts: 152




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« on: July 10, 2012, 10:31:12 AM »

Carolina Windom 80 special, having just put up the support pole for the short leg off my Carolina windom80s today I am planning on taking the other longer leg straight down to the bottom off my garden where there is a tree situated where I am going to tie the second leg off the windom to. the questions I have are :

1/ would it effect the performance off the antenna if the antenna was tied to the main trunk off the tree but within the foliage  ?? or would it be advisable to fit a short pole to take the end off the dipole above the tree and obviously clear off this foliage ??

2/ should the vertical section off the CW80s be kept 100% straight ot would taking it at a slight angle be okay for joining up with the main feeder coax ??
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KG6YV
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« Reply #1 on: July 10, 2012, 10:45:44 AM »

I have had a Caroline Windom 80 (133 ft.) in the air since 1996.  The short end is tied about 40 ft. up to a pole inserted in a large tree.  The antenna wire comes thru the tree foliage for about the final 10 ft.  The longer wire goes thru another tree in a similar fashion.  I have noticed no degradation in performance although I only use the antenna on 80/40M. 

As for the vertical radiator, I doubt if it makes much difference if the wire is still primarily vertical.  The biggest no-no is to have the vertical section within 20 ft. or so of any metal structure like a tower....

Greg
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GM1ZVJ
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« Reply #2 on: July 10, 2012, 11:12:31 AM »

Greg thats exactly the information / answers I was looking for ! thank you so much !

to be honest although yes a short pole within the tree would take the antenna slightly higher I feel I would get a better, more secure fixing with it fixed directly to the tree itself and this will hopefully pull up the slack on the line and help bring the heavy vertical section slightly further up from the ground.

have two off these spring tensioners that I plan to use   at both ends off the windom to hopefully get the dipole length that bit tighter to again hopefully bring the centre section slightly up which is proving to be a bit off a problem due to the combined weight off it !!

unfortunatly this end only have around 25 feet in height one end down to around 22 feet or so at the far end although it is going to be in one complete straight line so thats fine.

anyway thanks once again, your advice is much appreciatted.

john - gm1zvj
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GM1ZVJ
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« Reply #3 on: July 10, 2012, 11:54:05 PM »

Just wonder if anyone here has replaced the rg58 coax within the vertical section off the CW80S with ladder line ?? been advised that this   indeed cure the sagging problem. having never used this 300 Ohm line before just wonder what would be involved in replacing it on this particular antenna and if there would be likely to be any downsides to doing so ??

regards.
john - gm1zvj
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K4SAV
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« Reply #4 on: July 11, 2012, 07:38:14 AM »

Just wonder if anyone here has replaced the rg58 coax within the vertical section off the CW80S with ladder line ??

That's probably a bad idea.  The ladderline section is supposed to radiate and the choke is there to hopefully keep the coax below it from radiating.  In truth, the ladderline section radiates very little (contrary to what manufacturers would have you believe).  Its main effect is in changing the SWR on 15 meters.  The choke does reduce the amount of radiation from the coax but there is still lots of common mode current on the coax (as evidenced by the large number of people that have RFI with this antenna).

If you change the ladderline length that will probably change the SWR on several bands and depending on the ladderline length may cause the ladderline to radiate significantly, which will probably make the RFI problem worse.  Of course if you use ladderline all the way to the tuner at the rig, then SWR may not matter much, but the reason for using an off-center-fed design was to allow relatively low SWR so that it could be fed with coax.   If you are going to use ladderline all the way to the shack, then you would be better off using a center fed antenna with no chokes or baluns.  In other words, take the Carolina Windom down and replace it with a ladderline fed dipole.

The 4 to 1 balun at the feedpoint is a voltage mode balun which allows the ladderline below to radiate.  You could convert this to an OCF antenna by replacing the balun with a 4 to 1 current mode balun, but you would have to use coax for the feedline.  To use ladderline you would need a 1 to 1 current mode balun designed to operate at high impedances (300-400 ohms on some bands and much higher on others) over a wide frequency range.  I don't know of any source for a balun like that.

Jerry, K4SAV
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WB6BYU
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« Reply #5 on: July 11, 2012, 09:33:16 AM »

Quote from: GM1ZVJ

Just wonder if anyone here has replaced the rg58 coax within the vertical section off the CW80S with ladder line ??




My first ham antenna was an OCFD fed with 300 ohm twinlead.  True, it doesn't sag as much
as using coax to a balun.  I managed 4 contacts in the first 4 months of operation.  While
you might do better than that, I really can't recommend that approach.
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GM1ZVJ
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Posts: 152




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« Reply #6 on: July 11, 2012, 01:15:53 PM »

Appreciatte the information guys have now put that idea to bed !! will stick with getting this windom as high up as I can and hopefully get the vertical section that bit higher and without too much sag !!

thanks again.

john - gm1zvj
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GM1ZVJ
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Posts: 152




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« Reply #7 on: July 12, 2012, 09:43:58 AM »

Read off a few folk saying that they are using 86 feet off rg58x coax to feed the cw80s as per the recommendation by Radioworks, can see no ref to this within the notes included with my one, anyone confirm if indeed 86 feet off cable is a must to get a good match on the various bands ??

having just measured my own length off rg58 I see I only have 82 feet, likely to make much difference ??
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WB6BYU
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« Reply #8 on: July 12, 2012, 09:52:15 AM »

If the length of the 50 ohm coax affects the SWR, then the antenna needs a
better balun.  (Which may be the case.)

Your coax length should be fine.
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GM1ZVJ
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Posts: 152




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« Reply #9 on: July 12, 2012, 11:19:29 AM »

If the length of the 50 ohm coax affects the SWR, then the antenna needs a
better balun.  (Which may be the case.)

Your coax length should be fine.


Okay thats fine thank you for that, to be honest again I honestly cant see where it mentions within the Radioworks manual this recommended length off coax and just wondered why a few had mentioned it. anyway thanks again for your kind assistance.

 
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WB6BYU
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Posts: 13149




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« Reply #10 on: July 12, 2012, 12:59:33 PM »

There is a lot of ham radio "lore" about magic feedline lengths.  While there are a
few situations where it can make a difference, most of the myths, at best, are
based on assumptions that don't apply to most ham stations.

You can't say that a particular length of coax is non-resonant in actual use until
you consider everything that is attached to both ends of it.
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GM1ZVJ
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Posts: 152




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« Reply #11 on: July 14, 2012, 02:07:54 AM »

Okay guys, the windom 80 special is now up and just need to get the rg58 coax cable from the shack down the wall into the garden and then onto  the antenna itself.

within the link is a picture off the finished result, nowhere near as heigh as I would have liked it, 22 feet one end down to around 20 feet at the far end, main thing is the vertical section is in the clear and  off the ground !!   

have taken the vertical section towards the wall as looks slightly better so hopefully this will be okay - comments ??

thanks again for your kind assistance guys appreciatte that.

john  - gm1zvj

http://i280.photobucket.com/albums/kk191/jono400/SAM_2230.jpg
 
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WB6BYU
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« Reply #12 on: July 14, 2012, 07:34:03 AM »

Personally I wouldn't worry about the "vertical radiator" section all that much.
On the bands where vertical polarization is useful at low heights, it is too
short to radiate much.  On the higher bands where you might actually get
significant radiation from that section, the horizontal wire has more gain at
low angles.

As far as I can tell, the primary purpose of the vertical section is to improve
the SWR on 15m, where such an antenna otherwise doesn't give a good match.

But, in the process of keeping that section vertical, at least it means that your
feedline doesn't run too close and parallel to the main wire, which helps to
discourage some poor installations.
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