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G8MNY > TECH 20.06.13 15:10l 94 Lines 4046 Bytes #999 (0) @ WW
BID : 26852_GB7CIP
Read: GUEST
Subj: Band 2 6el Narrowband Yagi
Path: IZ3LSV<IV3YXW<I3XTY<I0OJJ<VE3UIL<JE7YGF<GB7CIP
Sent: 130620/1045Z @:GB7CIP.#32.GBR.EU #:26852 [Caterham Surrey GBR] $:26852_GB
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (Corrected Feb 13)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
Well I finally got around to it, I re-designed the large 6el broadband beam I
previously made using the MMANA-GAL program (CD 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. Orginally I wanted it to do
the whole 20MHz of UK's 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 of 103.4MHz.
2x
717 4x
³mm 640
³ Śæmm 2x 2x
³ ³³ 623 2x 620 2x
³ ³³ ³mm 601 ³mm 596
³ ³³ ³ ³mm ³ ³mm
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 mm ³³ mm ³ mm³ mm ³ mm 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 Strange lengths!
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" & "Coiled Coax Choke Balun for VHF"
Why don't U send out an interesting bul?
73 De John, G8MNY @ GB7CIP
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