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G8MNY > TECH 07.10.12 20:20l 95 Lines 3981 Bytes #999 (0) @ WW
BID : 61772_GB7CIP
Read: GUEST
Subj: Band 2 6el Narrowband Yagi
Path: IZ3LSV<IV3YXW<HB9TVW<IK2XDE<ON4HU<SR1BSZ<WA7V<XE1FH<JE7YGF<GB7CIP
Sent: 121007/1911Z @:GB7CIP.#32.GBR.EU #:61772 [Caterham Surrey GBR] $:61772_GB
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (New Sep 12)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
Well I finally got around to it, a re-designed a large 6el broadband beam using
the MMANA-GAL program (CD in 2010 RSGB yearbook & online).
The community radio station SUSY RADIO I do the engineering for, is too far
away to hear at my QTH for a normal small aerial, so I needed a good aerial on
103.4MHz. Orginally I wanted it to do the whole 20MHz of Band 2 87.5-108MHz.
But that was a mistake, as at my QTH I have strong QRM of the back of the
aerial, so I re-optimised the design for best front to back ratio on the one
frequency!
2x
717 4x
³cm 640
³ Śæcm 2x 2x
³ ³³ 623 2x 620 2x
³ ³³ ³cm 601 ³cm 596
³ ³³ ³ ³cm ³ ³cm
³ ³³ ³ ³ ³ ³
³ ³³ ³ ³ ³ ³
³ ³³ ³ ³ ³ ³
³ ³³ ³ ³ ³ ³
³ ³³ ³ ³ ³ ³
ĆÄÄÄÄÄÄÅ0ÄÄÄÄÄÄÄÅÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ 353 ³³ 477 ³271³ 796 ³ 741 ³
³ cm ³³ cm ³ cm³ cm ³ cm ³
³ ³³ ³ ³ ³ ³
³ ³³ ³ ³ ³ ³
³ ³³ ³ ³ ³ ³
³ ³³ ³ ³ ³ ³
³ ³³ ³ ³
³ ³³
³ ĄŁ
³ 80mm dia Elements Ally tube 20mm dia.
folded ends.
POLAR DIAGRAM
_-~~~-_ 8.54dBd
/ \
Ž Ż
Ž Ż
\ /
\_ _/
>ś<
< >
~-~
AERIAL IMPEDANCE
The is a good 75 Ohm balanced, so just a 1/4 wave coax choke balun is needed in
the coax feeding the connection box.
SWR 75ź .==========================.
³~-._ ((Folded Dipole ))
20´ '~-..__ '========(0) (0)========='
³ ~~-. \ / _ _ _
10´ '. COAX CHOKE³ ³_/ \/ \/ \____
³ ś. _..- 1:1 BALUN ĄÄo)_/\_/\_/\coax
1Å '--'' Just under 1/4 wave of coax~~~~
87.5 92.75 97.5 102.5 107.5MHz coiled up near the connection box
R ź X ź
150´ 250´
³-._ ³ _.-'
100´ ~-. __ 0´ _.-'~
³ ~-. __..--'' ''- ³ _.-'~
50´ '-.-'' -250´ _..-~
³ ³ _..-'
0´ -500´..-'
87.5 92.75 97.5 102.5 107.5MHz 87.5 92.75 97.5 102.5 107.5MHz
GAIN dBd F/B dB
12´ ³
³ ...- 32´
9´ ..--''' ³ .--''-..__.
³ -' 12´ --''~
6´ __..--._.' ³~~--._..--''
³.--'' 8´
3´ ³
87.5 92.75 97.5 102.5 107.5MHz 87.5 92.75 97.5 102.5 107.5MHz
IN USE
This works well on 103,4MHz. I can now hear my station with very little QRM.
Gain about 2dB better than the broadband version & F/B ratio 22dB not 11dB.
See My Tech Bul "Band 2 6el Broadband Yagi"
Why don't U send out an interesting bul?
73 De John, G8MNY @ GB7CIP
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