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G8MNY > TECH 09.09.11 07:29l 57 Lines 2841 Bytes #999 (0) @ WW
BID : 12636_GB7CIP
Read: GUEST
Subj: 6m Yagi from TV Antenna
Path: IZ3LSV<IW0QNL<ON4HU<IK2XDE<DB0RES<ON0AR<GB7CIP
Sent: 110909/0040Z @:GB7CIP.#32.GBR.EU #:12636 [Caterham] $:12636_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
From: DG0OPK @ DB0PV.#BAY.DEU.EU (Michael)
Hallo All,
After I am qrv on the 6m Band since May 2000 I tried to find out an
inexpensive solution to set up a short yagi for the band which was also posible
to use for scilly island expedition in august 2000.
So I asked my pit (DM2CKK) for some low expensive material. He found an old 4El
Yagi for CH-E3 TV Band. The boom length an the element spacings were not
modified because of the low space to put the yagi into the car for expedition
use so the boom length must be below 2 meters.
With the data of the yagi I started an antenna simulation... I want to find an
optimum gain with short boom with good VSWR & an moderate bandwidth to use the
yagi also in critical environment (that means the data should not so strong
differ from free space environment an mounting very low over the roof).
Here are the results of optimization ....
-------------------------------------------------------------------------------
ELEMENT: LENGTH (cm.) SPACING FROM REF. (cm.) ELEMENT DIA. (cm.)
Reflector: 290.0000 0 1.20000
Driven Ele.: 285.0000 91.5000 1.20000
Director #: 1 255.0000 138.0000 1.20000
Director #: 2 240.0000 184.5000 1.20000
-------------------------------------------------------------------------------
Normalized Radiation Resistance at 50.500 MHz is 43.34 Ohms
-------------------------------------------------------------------------------
FREQ (MHz) GAIN (dBi) F/B (dB) IMPEDANCE (ohms) VSWR
49.500 7.33 9.02 37.61-j8.39 1.32
50.000 7.36 11.79 41.51-j3.18 1.12
50.500 7.35 14.65 43.30+j1.15 1.00
51.000 7.34 17.79 43.19+j5.62 1.11
51.500 7.36 21.64 41.61+j10.78 1.26
52.000 7.41 27.52 39.00+j16.89 1.48
52.500 7.50 41.04 35.73+j24.06 1.83
------------------------------------------------------------------------------
I used this antenna with good results in the expedition for tropo contacts from
in69uw. I got very good reports all over europe in may 2001 were i used this
antenna at my home qth in jo50 & using only 10W output. I heard on also DX
(CX,PY).
The driven element is the a folded dipole from the TV-Antenna with an simple
1:4 balun using aircell coaxial cable. All elements were expanded from the
original size with aluminium rods & mounted with electrical contact to the
20x20mm boom.
So that's all ....
best greetings de dg0opk (michael)
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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