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G8MNY > TECH 08.01.05 12:48l 57 Lines 2371 Bytes #999 (0) @ WW
BID : 28002_GB7CIP
Read: GUEST
Subj: Stacking, Baying or Boxing Ant
Path: DB0FHN<DB0RGB<DB0MRW<OK0PPL<DB0RES<DK0WUE<7M3TJZ<HG8LXL<ON4HU<GB7YFS<
GB7KHW<GB7CIP
Sent: 050108/1111Z @:GB7CIP.#32.GBR.EU #:28002 [Caterham] $:28002_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (New Jan 05)
AERIAL SPACING
Aerial spacing, is variable, the manufacturers data may help, but a good guide
is about half the boom length for yagies & 2/3 boom length for QLY & ZLs. This
rule of thumb, makes sure the aerials capture areas (as if they were dish
aerials) do not overlap.
Gain
+3dB Ä´ _..------
+2dB Ä´ ,/''\._ _./'
+1dB Ä´ ./'\ / '
0dB _³_.,/' '-.-'
ÄÅÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄ> Spacing
Touching Too Close Half Boom
Close Optimum Length
Closer stacking or baying, gives variable results as all the aerial elements
will couple, & this will result in a different polar diagram & gains less than
optimum. But closely mounted aerials with high gains are possible, if difficult
to get the distance just right for one spot frequency!
STACKING, BAYING or BOXING AERIALS
The aim of using more aerials is to improve performance by reducing aerial beam
lobe size to increase gain.
___ __
,/ \ ______ /' '\ __
/ Aerial `\ ./' `\. ³ « ³ ./' `\.
³ Lobe ³ ³ « Area ³ ³ Area ³ ³¬ Area³
\ Area / `\.______./' ³ ³ `\.__./'
`\ ___ /' \.__./
1 Aerial 2 Aerials Stacked 2 Aerials Bayed 4 Aerials Boxed
Gain/one 0dB 3dB 3dB 6dB
From these plots you can see that stacking offers gain without the reduction
horizon beamwidth, or contact opportunity, that baying 2 aerials has or even 4
Boxed aerials with its nice 6dB gain.
Another point often forgotten is that both aerials should see the same RF field
to work. If one aerial is much closer to the ground or buildings it can cancel
any advantage as Rx signal power can actually be lost in the lower aerial!
ÃÅÅÅÅÅ <- - - - - - - - Even Dx
³ _ <- - - - RF Field
ÃÅÅÅÅÅ -> / \ <- - -
³ ³ ³
ÄÄÄÁÄÄÄÄÄÄÄÄÄÁÄÄÄÁÄÄ
See my bulletins on 4x Power Splitters for 2M & 70cm, Making a Phasing Harness.
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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