2 Element 40M Delta Loop at N4KG
I used the formula lengths (DE = 1005/F and REF = 1040/F)
fed at the center of the bottom part of the loop with RG59 going
to 75 ohm hardline for a total length that was an odd number of
quarter wavelengths, making a 100 ohm to 50 coaxial transformation.
(I put aligator clips on the shack end and spliced in various lengths
of RG59 until I found the 50 ohm point, then made a permanent
piece of RG59 to connect the hardline to my antenna switch.
You can also feed at the apex, whichever is easier.
To make reversible loops, make both loops the same size (1005/F)
and feed each with 3/8 wavelength (electrical) of RG59. Use relays
to switch BOTH the center conductor and braid. The open ended
line will transform to an inductance at the unfed loop, making it look
like a reflector. Continue with 75 ohm line to make an odd number
of quarter wavelengths to transfrom 100 ohms to 50 ohms.
K1ZZ used this technique years ago and had excellent F/B in
Alabama when he switched directions.
For short towers (less than 90 ft), it may be preferable to use
vertically polarized delta loops, feeding 1/4 wavelength down
from the apex. If the bottom wire of the loop is close to ground,
you may need to shorten the loops by 3.5% (that is my experience
with single 80M loops whose bottom wire is10 ft above ground.)
Two element inverted vees also make sense with towers in the
70 to 100 ft range. It is desirable to make the apex angle >120
degrees if possible. (One advantage of the delta loops is that
the apex angle is only 60 degrees, requiring less real estate
but greater height. A 40M equilateral Delta Loop is
approximately 40 ft in height.)
Of course the Delta loop may be scaled to any band. A single
sloping rope may be run from a tower, supporting delta loops
for several bands, all in the same direction. From the Carib,
run one line to EU and another to USA/JA. Good gain, low cost,
easy to install. All you need is one sufficiently high support!
de Tom N4KG
On Mon, 24 Nov 1997 12:56:32 -0800 "ALEXANDER A. AIMETTE" <w2ox@fast.net>
writes:
>T A RUSSELL wrote:
>>
>> Fixed Beam Heading Preferences de N4KG
>>
>> >From the EASTERN USA, the answer is simple: 60 degrees.
>> At one time I had a 2 element Delta Loop supported by a 20 ft boom
>> attached at the 120 ft level on a 130 ft tower, aimed at 60 degrees.
>> This antenna was a KILLER to Europe, Africa, Middle East, and Indian
>> Ocean.
>> If I had made it reversible, then I could have added the South
>Pacific.
>> A pair of such antennas would cover the world by adding one for
>JA/SA.
>>
>> BTW, these headings also make sense for 4 SQUARES, instead of the
>> conventional NE,SE,SW,NW with their nulls at N,S,E,W. By rotating
>15
>> degrees clockwise, the 4 square crossovers then become 15, 105, 195,
>> and 285 degrees. From the Eastern USA, (almost) nobody lives at
>> those headings!
>>
>> de Tom N4KG
>> ............................
>>
>> On Mon, 24 Nov 1997 04:01:13 +0000 Mike <no6x@inreach.com> writes:
>> >I know this may seem like a stupid question but it is of valid
>reason
>> >to me.
>> >
>> >If you were to have a wire beam up for 80 meters and had to fix it
>one
>> >direstion for contests. which way would you point it? Oh yeah this
>is
>> >from
>> >the west coast!
>> >
>> >Is it better to work a bunch of 3 points apiece contacts ,or is it
>> >better
>> >to get the multipliers from EU? (which I am not sure of how well
>that
>> >would
>> >work anyway)
>> >
>> >My solution was point it at JA and get all you can. Or am I even in
>> >the
>> >correct part of the compass, maybe I need SA, or VK, I DONT KNOW!
>> >
>> >OK, Now who knows the "correct" answer?
>> >
>> >New at this contesting and ready to kick some more butt.
>> >Mike...NO6X
>> >
>> >P.S. this ant design will be mainly for DX contests.
>> >
>> >
>> >
>> >Check out my home page at http://home.inreach.com/no6x
>> >
>> >--
>> >CQ-Contest on WWW: http://www.contesting.com/_cq-contest/
>> >Administrative requests: cq-contest-REQUEST@contesting.com
>> >
>>
>> --
>> FAQ on WWW:
>http://www.contesting.com/towertalkfaq.html
>> Submissions: towertalk@contesting.com
>> Administrative requests: towertalk-REQUEST@contesting.com
>> Problems: owner-towertalk@contesting.com
>> Search: http://www.contesting.com/km9p/searchTOM:
>I have 200 foot tower at v47kp with one delta loop facing 45
>degrees. I might be able to put a boom up there and stick a second
>delta
>loop off the back of the tower. Can you give me any details on the
>pair
>you had up where fed? how long each one? open circuited etc. I was
> also thinking of a wire beam off the front of the tower hanging from
>a
>catenary going out maybe 600' to a tree at about 100' level towards
>europe any info on that kind of beam two ele vs 3 el how feed?? any
>info
>would be helpful? Answer direct or to reflector cuinpups this
>weekend
>73 alex w2ox/v47kp
>
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