3EL Yagi Kit |
I contributed this article to Japanese CQ HAM RADIO June, 2010
I do a lot of QSO to Japanese HAM with this antenna
and QSO is possible with European HAM
(My Transceiver is FT-1000MP only 100W) |
Make Inverted-V antenna
100 degrees are most suitable for an element
Because antenna impedance becomes 50 ohm
If an element angle is 180 degrees,
antenna impedance becomes 75 ohm
Transceiver and an antenna become Miss matching
You have to use high quality balun.
1)Prevention of interference
2)The efficiency is good and cuts an radio wave in ONAIR
Length of an element is found with the following calculations type
L=75 / f * 0.95 1/4lambda element(m)
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Diamond Balun
BU50 |
When the outside of a band will calculate, adjustment is easy
Frequency |
Length (1/4lambda) |
6.95MHz |
75/6.05*0.95=10.25m |
7.00MHz |
75/7.00*0.95=10.18m |
7.05MHz |
75/7.05*0.95=10.11m |
7.10MHz |
75/7.10*0.95=10.04m |
7.15MHz |
75/7.15*0.95=9.97m |
7.20MHz |
75/7.20*0.95=9.90m |
7.25MHz |
75/7.25*0.95=9.83m |
Frequency |
Length (1/4lambda) |
3.50MHz |
75/3.50*0.95=20.35m |
3.55MHz |
75/3.55*0.95=20.07m |
3.57MHz |
75/3.57*0.95=19.95m |
3.60MHz |
75/3.60*0.95=19.79m |
3.68MHz |
75/3.68*0.95=19.36m |
3.70MHz |
75/3.70*0.95=19.25m |
3.75MHz |
75/3.75*0.95=19.00m |
3.79MHz |
75/3.75*0.95=18.79m |
3.80MHz |
75/3.75*0.95=18.74m |
How do Adjustment
If you have a SWR analyzer,
adjustment of an antenna is very easily.
You do not have? ok, please next step. |
SWR ANALYZER
MFJ-259B |
install an antenna wire to balun.will cut a wire longer than a calculation
value
Please do not connect an antenna tuner this time.
It is to make a good antenna of the efficiency most.
Even if an antenna tuner can protect your Transceiver, but cannot do ONAIR
of a strong signal.
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you adjust length of an element so that 1.5 values of a SWR meter become
equal to or less than it.
if 7MHz shorten an element every 7cm
You do not have to cut an element.
You turn down an element and wind it.
If you shortened too much an element, can lengthen it easily
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If your land does not have space, you can bend an element
you can bend an element
But some efficiency of an antenna becomes bad
and an element length is different from a calculation value
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You can one balun can install a different element
and You use an element of 7MHz, and ONAIR is possible to 21MHz.
If do ONAIR to 21MHz, please use an antenna tuner.
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Please enjoy DXing
DX station expects QSO with Philippine HAM
Copyright ©2010 Kouichi Ueno JI1FGX/DU9 All Rights Reserved |