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about HF antenna
Inverted-V fot 40m how to make of an Inverted-V antenna
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)

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.
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


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




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.



Please enjoy DXing
DX station expects QSO with Philippine HAM


Copyright ©2010 Kouichi Ueno JI1FGX/DU9 All Rights Reserved
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