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G8MNY > TECH 26.09.12 08:24l 79 Lines 3366 Bytes #999 (0) @ WW
BID : 60377_GB7CIP
Read: GUEST
Subj: Broadband 6el Yagi for Band 2
Path: IZ3LSV<IW0QNL<ON4HU<CX2SA<ZS0MEE<GB7CIP
Sent: 120926/0032Z @:GB7CIP.#32.GBR.EU #:60377 [Caterham Surrey GBR] $:60377_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)
The community radio station I put on, is too far to hear at my home really, so
I needed a good aerial. I designed this one from a well engineered but very
old scrap Band 2 aerial as a starting point using the free MMANA-GAL aerial
design software.
I wanted it to do well over the whole 20MHz of Band 2, but this caused a real
compromise in the preformance!
All the elements use 10mm dia tube.
____________________1698mm
Distance 326cm
98mm-ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿1292mm _ ~10dB
-ÀÄÄÄÄÄÄÄÄooÄÄÄÄÄÄÄÄÙ2x731mm / \ F/B
Distance 186mm Back ³ ³
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ lobe \./
.-~ ~-.
Distance 713mm / \
³ ³
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ 1228mm ³ ³
³ Front ³
Distance 716mm \ Lobe /
'-._.-'
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄ 1166mm +8dBd
Distance 715mm
ÄÄÄÄÄÄÄÄÄÄÄÄ 1041mm
SWR 300ê
4´ Matching the approx 300ê balaced to 75ê
³ 75ê coax was done using a tiny 4mm VHF
3´\ ³ ferrite ring with the centre tap of 6
³ \ / turns to the braid.
2´ \ / __()))))__Ant
³ '-.______ _.-' Ant ³ ³___
1Å ~~~~~~~~~ ÀÄo)coax
87.5 92.75 97.5 102.5 107.5MHz ~~~~
R ê X ê
400´ __ 200´
³ .-~' ~-. ³
300´ .-~ \ 100´ _...._
³ .-~ \ ³ .ú'~ 'ú.
200´ .-~ '. 0´.' \ /
³.-~ . ³ 'ú._ _.ú'
100´ . -100´ ~
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
10´ / 15´_ _
³ / ³ -. _.-'
9´ .' 12.5´ 'ú. _.-'
³ _.-' ³ '-..__..-'~
8´~-. _.ú'~ 10´
³ '---....-ú' ³
7´ 7.5´
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 75ê SWR was quite flat as above. But now regret I did not
designed it to be a spot frequency narrow band 1MHz wide aerial, as that would
give 2-3dB more gain & > 22dB F/B ratio. The back of the beam QRM is the main
problem I have! :-(
See TECH Bul "FM Stereo Radio Principles"
Why Don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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