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Author Topic: Home brew windom Anyone made one ?  (Read 503 times)
N2UNL
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Posts: 15




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« on: March 31, 2008, 10:39:31 PM »

I wish to build a OCF multiband dipole as the windom. I have 14g. wire and will be feeding it with a coax all the way to the balun. Would like to know wich balun should be used the 4:1 or 1:1 ?  This ant will be the short multiband 10-80 version also around 135' total. Anyone know what the measeurements I should use for the wire length for each side ?                     Thank You, Brian
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N6AJR
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« Reply #1 on: March 31, 2008, 10:46:57 PM »

Buxcomm.com has some good info on building one
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G8UBJ
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Posts: 478


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« Reply #2 on: April 01, 2008, 01:53:33 AM »

I think you will require a good ATU for the Windom.

http://www.g4nsj.co.uk/windom.shtml

I was looking at an article on the good ol' G5RV and noticed this antenna which promises to be superior.

http://www.cebik.com/wire/g5rv3.html

"The ZS6BKW/G0GSF Antenna System is only about 93 ft... 5 bands with one doublet and no ATU is no mean feat"

has anyone tried it?
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G8UBJ
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« Reply #3 on: April 01, 2008, 01:58:08 AM »

1:1 and 4:1 balun required and it needs to be up high 32' + Quite honestly I think thats the secret.. even the lowly G5RV jr works well at a good hight.

73 G8UBJ
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AC5UP
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Posts: 3908




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« Reply #4 on: April 01, 2008, 06:24:38 AM »

I had an OCFD for several years that worked the world on 100 watts SSB. The only time I needed the internal tuner was at the edges of 75 / 80 meters and the high end of 40. Otherwise it was plug & play into 50 ohm coax for 20, 17, 12 and the bottom 1 MHz of 10. No-Go on 30 and 15.

Supports were a pair of 30' push-up TV masts topped with 5' of grey PVC conduit as the masts were 120' apart and the wire needed some separation from the mast. About 8' of wire at each end drooped a bit, average height of the middle section was around 30'.

I started with 136' of 10 ga THNN stranded wire, cut 45.5' from one end. Feedpoint used a home-brew 4:1 Guanella dual-core "current" balun wound with #18 stranded silver teflon wire on "43 material" 1.25" cores. Do not use a single-core "voltage" balun. You want near equal current in both legs.

Get the wire up in the air, route the coax as it will likely be permanently installed, then take SWR readings at the radio and mark them down in chart form for each band. Prune only the long end of the wire by an inch or two if needed. Re-chart your SWR readings per band and decide if you want to prune another inch or two. Look for the best compromise in the band segments of interest to you and think it over before you cut again. You'll be juggling variables on multiple bands. An overall best compromise is what you're looking for.

The antenna was adequate for regional use on 80, 'continental' coverage on 40, DX on 20 through 10. It will not load on 30 or 15, but there is a way to add a vertical drop wire on the long leg for 15 and perhaps 30 meters. I never bothered. The rig here won't TX on 60 unless I do a mod so I have no comment on that. Purists will argue that tuning the antenna by SWR at the radio end of the coax is poor form, but that was the most practical method I could come up with.

General coverage RX is excellent from AM BCB through 10 meters and it will load on six, but don't expect to outperform a Ringo with it. Likely the balun is struggling at that frequency. First Q I made with mine was into Croatia on 12 and I took that as a good sign that it works. The wire was aligned true north-south with the short leg to the south. This gave a nice cloverleaf pattern on 20 to the NE, SE, SW and NW which worked well for me into EU and OZ... Had the wire been run east-west it would likely have done the same. Best DX was into Johannesburg and Durban Sud Afrika on 20. Considering that's about half way 'round the world I figured that was "good enough".
 
Wink
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WW5AA
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Posts: 2086




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« Reply #5 on: April 01, 2008, 07:33:13 AM »

I have built several Windom antennas, both the original which is fed with a single conductor and the variants as advertised by the commercial bunch. All my antennas are tested side by side at 70'. The only reason I would use any of them would be if it was necessary to have an OCF because of geography. In no case were any of them as good as my plain old doublet. The last one I fooled with was 90' and 30'. A coax fed Windom, which is not Windom anymore will be very inefficient with or without a balun at the feed point.

73 de Lindy
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KB1LKR
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Posts: 1898




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« Reply #6 on: April 01, 2008, 10:01:52 AM »

Loren G. Windom, W8GZ (SK - 1988) wrote an article in QST, September 1929, pp 19-22, if you don't have QST that far back a search on his name will yield plenty of info. Get some copper-weld or other copper clad steel wire and go nuts!

So why is Louis's antenna called a "G5RV" not a "Varney" but Loren's is called a "Windom" not a "W8GZ"?

I'm guessing Hidetsugu Yagi & Shintaro Uda were not licensed amateurs, hence the name "Yagi" (or more properly "Yagi-Uda"), of mid 1920's vintage.

In any case this could be more material for KA4KOE's series of "Dead Electrical Dudes" articles!
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WB2WIK
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« Reply #7 on: April 01, 2008, 10:03:30 AM »

The OCF doublet balun is normally a 6:1 Z-ratio to achieve best match over the bands.  Any ratio is a compromise, but I see the "big company" OCFs use a 6:1, which is obviously a custom balun with a turns ratio of about 2.5:1.

Probably 6 turns primary and 15 tuns secondary on the proper ferrite core would work okay down to 3.5 MHz.

WB2WIK/6
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WE1X
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Posts: 340




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« Reply #8 on: April 01, 2008, 02:36:24 PM »

Been using an 80m-10m OCF for 12 years. Feed point up about 35 feet. SWR less than 1.8:1 on all bands with exception of 30m and 15m, but external tuner handles them nicely. How does it perform? Worked VP6DX (Ducie Island) on 80/75m and 40m with no problem.

Harry WE1X
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WA3KVN
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Posts: 18




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« Reply #9 on: April 02, 2008, 05:42:59 AM »

I offer the following information about my home-brew Carolina Windom antenna.

Overall Length (2 sections) - 83ft + 50ft (at 3.51MHz that's 0.62 wave + 0.38 wave).
Wire size - 12 gauge.
Center balun - 4:1 (BuxComm BuxBalun41, Evington, VA).
In-Line Choke - Ferrite Beads (Palomar Engineers, Model BA-58 Balun Kit).
Feedline - 50 ft. of RG-8X coax.

Center the In-Line choke on the feedline at 22ft from the Center balun.  This style of in-line choke is non-traditional and may even be somewhat novel!  Make sure the feedline hangs straight down at least to the in-line choke.

This antenna is hung, flat-topped at about 30ft in the air.  My Yaesu FT-1000 M5 tunes it on all bands 80 - 10 meters.  SWR is perfect on 20 meters, but it varies on the other bands.  The center balun (I believe) overheats quickly on 30 and 160 meters
sending the SWR soaring, but I can get short QSOs on these bands.  Otherwise the combination works perfectly.

I haven't the benefit of a comparison antenna; however, I worked WAS (basic + CW) and DXCC (mixed) in the past 5 years of ever-dropping sunspot cycle activity.

Charlie, WA3KVN
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WA3KVN
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Posts: 18




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« Reply #10 on: April 02, 2008, 06:47:46 AM »

Just a quick correction on my antenna wavelength calculation.  Change overall length in my previous post to:

Overall Length (2 sections) - 83ft (62%) + 50ft (38%); at 3.51MHz the overall length (133ft) is 1/2 wave.

Sorry for the confusion,
Charlie, WA3KVN
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