6el YAGI for FM DX

High school students in Morioka 1st High School (JA7YAF) had a interest in long distance reception of Japanese FM stations so I built a original 6el YAGI with them.

OriginalFM 6el

Target

• Larger gain with a little nallower frequency range 78-81MHz
• Connect with 75ohm coax
• No adjustment, easy setup, no failure!

Design

1. I converted the data of 50MHz YAGI into 81MHz by multiplying 50/81. I choose 81MHz because the gain of YAGI decreases very much at higher frequency.
2. Adjusted on a simulator MMANA. According to the MMANA page it workes only on the Japanese versions of Windows.
3. Shortened the boom length to 4m.
4. Adjusted the length of radiator to lower VSWR. Compared the gain etc. to [2].
5. Shortened the length of directors for wider frequency range with a small loss.
6. Adjusted all elements/spaces length a little.
7. Compared the gain etc. to [2].

Building

Boom is a 4-meter pole. I could buy only four aluminum pipes of D=10mm, so 3rd/4th directors are stainless steel pipes of D=9.5mm.

Coaxial cable 5D-2V is connected directly to the radiator through two ferrite cores (used for a noise filters of computer cables) for a common mode filter.

Result

We built it 1.5m higher on the 6m tower. This tower is built on 16m height so the height is about 23.5m.

A: good / B: fair / C: poor

------------------------------------------------------------
MHz	Stations		QTH
------------------------------------------------------------
76.1	A FM Iwate		local
   9    A R. Morioka		local
77.1	A Date FM		Sendai (JA7 160km)
   7	C FM Akita		Honjo relay
   9	C FM Iwanuma		Iwanuma city, south of Sendai
78.0	B bayfm			Chiba (JA1)
   4	C FM Aomori		Hachinohe relay
   6	A Fukushima FM		Haramachi relay
   8	C FM Jonpa		Sendai
   9	C FM Akita		Kakunodate relay
79.2	B FM Iwate		Kamaishi relay
   6	A FM Tsubakidai		Yuuwa, Akita pref.
   7	C FM Izumi		Sendai
80.0	B TOKYO FM		Tokyo
	B FM Aomori		Aomori
   3	B FM Iwate		Ichinoseki relay
   4	C FM $B;37A(J		Yamagata
   	B AIR-G'		Sapporo
   7	B NHK Chiba		Chiba
81.3	B J-WAVE		Tokyo
	B FM Aomori		Mutsu relay
   6	A NHK Morioka		Murone relay
   8	B Fukushima FM		Fukushima
   	C NHK Aomori		Hachinohe relay
   9	C NHK Yokohama		Yokohama
82.1	C NHK Yamagata		Yamagata
   2	A FM Iwate		Fukuoka relay
   5	A NHK Sendai		Sendai
   7	C NHK Aomori		Mutsu relay
   8	A FM Akita		Akita
83.1	A NHK Morioka		Morioka
   4	B NHK Aomori		Kamikita relay
   8	B NHK Morioka		Ichinoseki relay
84.3	C FM Aomori		Kamikita relay
   6	C NHK Sendai		Kesen-numa relay
   7	C Fm yokohama		Yokohama
   9	B NHK Morioka		Kita-Fukuoka relay
85.1	B NHK Morioka		Kamaishi relay
   2	C NHK Sapporo		Sapporo
   3	C NHK Fukushima		Fukushima
   8	C NHK Akita		Kakunodate relay
86.0	B NHK Aomori		Aomori
   7	A NHK Akita		Akita
87.6	C NHK Morioka		Nishine-Matsuo relay