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G8MNY > TECH 31.12.07 00:21l 93 Lines 3779 Bytes #999 (0) @ WW
BID : 40752_GB7CIP
Read: GUEST
Subj: Balloon & Kite Aerials
Path: IZ3LSV<IW2OAZ<CX2SA<GB7CIP
Sent: 071228/0238Z @:GB7CIP.#32.GBR.EU #:40752 [Caterham] $:40752_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (Updated May 06)
(8 Bit ASCII Graphics use code page 437 or 850)
I have not tried this myself but have seen demonstrations at local club /P.
DIPOLES
T O P B A N D D I P O L E
Large
Left_____ _____Middle_____ _____Right
Kite '''ÄÄÄÄ''' Kite '''ÄÄÄÄ''' Kite
: 0.5mm wire? : º 100m :
: : º 75ê : Kite
: : º Bell/LS : String
: : º Wire : 200m
: : º Feeder :
: : º :
Up Wind Up Wind ÈÍBALUNÄÄo)RIG Up Wind
Tie Off Tie Off _³_ Tie Off
////
This one is huge & possibly needs Air Traffic notification if over 100m tall.
With the ground reflected signal, the aerial height alters the radiation angle
giving peaks & nulls at predictable heights depending on ground conductivity &
is the easiest parameter to adjust on this aerial.
The Left & Right kites tension the dipole & unless designed for sideways drift,
the strings have to take full dipole tension as well as the kite load & have to
be outspread from the dipole quite a bit to achieve this! So a large field is
needed for the 160m version to give plenty of safe unobstructed flying space.
It can also be repositioned once aloft for best dx direction, & will also need
repositioning the tie offs if the wind changes.
The centre kite has to be much larger to take half the weight of the dipole
plus the heavy balanced feeder.
In VERY light winds, Helium Balloons can be substituted for the kites, &
possibly several used for the middle load.
VERTICAL AERIAL
A simpler Omni Aerial
Kite or
Balloon
: ³
: ³Wire
: ³Aerial
: ³
: ³
: ÀÄATUÄÄo)Rig
Up Wind _³_
Tie off ////
The wavelength length of wire not only alters the Z seen but also the radiation
angle & hence the kind of skywave possible.
1/4 wave is ideal for a low Z aerial if you can get a really good earth (near
sea water etc.) & ground plane (3-10 1/4 wave long ground wires laid down).
1/2 wave aerials are OK but the drive Z ( >5kê ) may be a problem for the ATU
(Flashovers etc.) so sorter or longer (3/8 or 5/8) may prove an easier length
& safer slightly lower Z match. Also with medium Z aerials (600ê-3kê) the earth
currents are much reduced, reducing the need for a realy good earth or ground
plane.
SERIES L
If the Z is too high for your ATU try a series L. e.g. 34 turns on a toilet
roll tapped at 8 & 13, giving L steps of between 1.5 to 2.6 times.
TURNS L Change
<ÄÄÄÄ34ÄÄÄÄÄ> 5 1 0%
((((((((((((( 8 2.6 256%
³ ³ ³ ³ 13 6.7 264%
8 5 21 21 18 260%
<Ä13Ä> 26 27 153%
<ÄÄÄ26ÄÄ> 34 46 174%
SAFETY
Light aircraft are a hazard to flying aerials, although the aircraft minimum
height should ALWAYS be greater than 500ft (152m) above ground unless near
airports, it is not always so! Above 200ft (60m) you may need Air Traffic
Control clearance depending on the location!
Never Fly aerials if there is static around. No earth protects you from,
20,000 AMP flowing as a arc down your vaporised fuse wire aerial to YOU!
Why Don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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