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G8MNY > TECH 01.06.22 21:05l 119 Lines 4831 Bytes #999 (0) @ WW
BID : 22303_GB7CIP
Read: GUEST
Subj: Balloon & Kite Aerials
Path: IW8PGT<LU4ECL<JE7YGF<GB7CIP
Sent: 220525/0906Z @:GB7CIP.#32.GBR.EURO #:22303 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Aug 08)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
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 & needs Air Traffic notification if over 60m tall!
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.
EFFECT OF HIGHT
Nul
 o
1/4
Wave o _Radiation /|\ Max Radiation
up _- Angle ? Â o Angle
_- 1/8
\ _- Wave >Weak Signal
------------ Best ------------- ----------------------
/
o
Good Weak o Good
Ground Ground Ground
Image o Image Image
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.
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 to match. Also with medium Z aerials (600ê-3kê) the
earth currents are much reduced, reducing the need for a really good earth or a
ground plane. (set of counterpoises radials)
With tall verticals (1/4 wave or longer) there is no upward radiation & the
more local high angle signals disappear, to leave only the weak low angle DX
stations.
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 6 L steps of between 1 to 46 times the minimum
inductance by just clipping on the taps wanted.
TURNS L Step 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!
Roger G4ROJ (www.kiteaerials.com) wrote to me, that in the UK 200ft (60m) is
the highest you can fly kites without special permission & not within 5kM of
an airport!
Never Fly aerials if there is static around. No earth protects you from,
20,000 AMPS 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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