Login: GUEST @ JH4XSY.14.JNET1.JPN.AS [Tsuchiura]
home | newest check | boards | help index | log | ps | userlogin | send sysop | slog | status forward | bcm news | users | version | remove cookie
G8MNY > TECH 20.02.25 19:10l 97 Lines 4161 Bytes #7 (0) @ WW
BID : 26448_GB7CIP
Subj: Band2 6el Narrowband Yagi
Path: JH4XSY<IW0QNL<SR1BSZ<EA2RCF<LU9DCE<W0ARP<WW4BSA<N3HYM<EI2GYB<GB7CIP
Sent: 250220/1004Z @:GB7CIP.#32.GBR.EURO #:26448 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
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).
My 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 the aerial to
do the whole 20MHz of UK's Band2 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 just 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
This is a good 75 Ohm balanced on the design frequency, 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 92.5 97.5 102.5 107.5MHz coiled up (3-4 turns) near
the connection box.
R ź X ź
150“ 250“
³-._ ³ _.-'
100“ ~-. __ 0“ _.-'~
³ ~-. __..--'' ''- ³ _.-'~
50“ '-.-'' -250“ _..-~
³ ³ _..-'
0“ -500“..-'
87.5 92.5 97.5 102.5 107.5MHz 87.5 92.5 97.5 102.5 107.5MHz
GAIN dBd F/B dB
12“ 40“
³ ...- ³
9“ ..--''' 20“ .--''-..__.
³ -' ³ ,-''~
6“ __..--._.' 10“~~--._..--''
³.--'' ³
3“ 5“
87.5 92.5 97.5 102.5 107.5MHz 87.5 92.5 97.5 102.5 107.5MHz
IN USE
This works well on 103.4MHz. I can now hear my SUSY RADIO station with very
little QRM. Gain about 2dB better than the broadband version & F/B ratio 22dB
not 11dB.
See My Tech Bul "Band2 6el Broadband Yagi", "Coiled Coax Choke Balun for VHF",
& "FM Stereo QRM".
Why don't U send out an interesting bul?
73 De John, G8MNY @ GB7CIP
OĢ[ | Ģ[