JI1FGX/DU9 Amateur Radio Diary, Mindanao, Philippines, IOTA OC-130.
English. Japanese.



Yesterday's access.
Introduction. [Lily Diary.】
A diary of life in Mindanao.

25/09/13  3.5MHz SWR increased
25/09/12 3.5MHz Zepp antenna adjustment
25/09/10  Geostationary satellite QO-100
25/09/09  Preparing for the satellite station
25/09/08  DU9JJY satellite station
25/09/07  14MHz late at night
25/09/03  Mitsubishi Strada Pickup Truck
 Oil Change
25/08/18 WSJT-X Automatic operation Ver0.1.0
25/08/18  JTDX Autonomous operation Program Ver0.6.3
25/08/10  Software List
25/07/26 AutoCWType_Ver1.5.8
25/07/20  Create one month's worth of ADIF files from JTDX Ver 2.6.5
25/07/19  Japan's Radio Wave Usage Tax
25/07/13  IARU HF Contest
25/07/10 Software updates
25/07/08 DXV500ZS linear amplifier repair
25/07/07 CQ Machine Program
25/06/21 LoTW system upgrade
25/06/18 RG8 for 3.5MHz arrived
25/06/15  Time setting Ver0.5
25/06/14 Drone Habsan ZINO arrives
25/06/12 Philippine Independence Day
25/06/11 Algeria 7X2RF QSL card.
25/06/10 Translation API Program
25/06/09 DXCC150 award certificate arrived
25/06/08 AutoCWType_Ver1.4.1
25/06/07 Introducing the Shack
25/06/06 A portrait drawn by ChatGPT.
25/05/26 Windows full-width/half-width switching.
25/05/17 OK2ZAW BCD to 16 converter.
25/05/16 For 3.5MHz Zepp antenna.
Stepping motors
25/05/15 3.5MHz stepping motor design.
25/05/14 3.5MHz tuning coil installed.
25/05/11 3.5MHz antenna installation completed.
25/05/03 JTDX Autonomous Driving Program Ver0.4.3.
25/04/26 Drone Habsan ZINO.
25/04/25 Time setting Ver0.3.
25/04/24 AutoCWType_Ver1.3.
25/04/23 Preparing for FTDX3000 LCD repair.
25/04/22 Installation plan for 3.5MHz Zepp antenna.
25/04/21 AutoCWType_Ver1.1.
25/04/20 10,14MHz antenna installation completed.
25/04/19 JTDX Autonomous Driving Program Ver0.4.1.
25/04/19 14MHz antenna pole installed.
25/04/18 ThinkPad X390 repair completed.
25/04/17 Search is now possible.
25/04/15 Preparing the 10MHz dipole.
25/04/12 Hexbeam Part8.
25/04/06 My ThinkPad X390 is broken.
25/04/05. Time setting program.
25/03/31 JTDX Autonomous Driving Program.
25/03/30 Automatic log sending from CWType to Hamlog.
25/03/21 Hexbeam Part 7.
25/03/20 FreeDV Part 3 First QSO.
25/03/18 FreeDV Part 2 QSO in the shack.
25/03/16 Hexbeam Part 6.
25/03/15 Install FreeDV Part1.
25/03/09 Hexbeam Part5.
25/03/07 Hexbeam Part 4.
25/03/05 28MHz antenna modification
25/03/01 FTDX3000 is broken!
25/02/28 Pileup at 50MHz FT8.
25/02/28 DXV500ZS linear amplifier repair.
25/02/27 Tower pipe rebuilding plan.
25/02/26 Direction to Japan from Ozamiz.
25/02/26 28MHz is not available.
25/02/23 DXV500ZS linear amplifier repair.
25/02/22 Hexbeam Part 3
25/02/21 Hexbeam Part 2
25/02/18 28MHz antenna construction.
25/02/17 18,24MHz antenna height construction.
25/02/16 Z26NS Cosovo.
25/02/14 21MHz FT8
25/02/12 7,21MHz antenna repair.
25/02/08 Operating CW at 21MHz.
25/02/05 DXV500ZS linear amplifier failure.
25/01/19 Input Director.
25/01/14 Temporary license renewal.
3.5MHz Zepp antenna adjustment (2025/09/12)

October 15, 2024.My friend JK1SNS sent me an unused 3.5MHz Zepp antenna via EMS mail.
andMay 11, 2025.We carried out construction work to install elements.
RG8 coaxial cable 10m　2,995 pesos (approx. 8,000 yen)　I can't buy it.June 18, 2025.Purchased at last.
In August, the element on the 10m side came off the rope, so we asked a local junior high school student to climb up the tower and fix it.

And finally, on September 11th, we made the adjustments.
Wooden box containing the tuning circuit for the Zepp antenna
PVC pipe containing the coil and variable capacitor.
According to JK1SNS, it can be used from 3.5MHz and 3.8MHz to 7MHz.
When measured directly under the coil with a NanoVNA, the SWR and Smith chart were good.
However, when I measured the 40m RG8 coaxial cable at the shack side with the NanoVNA, the SWR was 2.0.
It is possible to go on air using the FTDX3000 antenna tuner, but it feels weird, so I decided to take measures.
Even after adding three snap cores, there was no improvement.
So I made a common mode choke by winding RG58 12 times around the ferrite core I had purchased for the 1:1 balun.
Then the SWR dropped to 1.21.
The tuning frequency has risen to 3.75MHz, so I adjusted the frequency using the coil tap and variable capacitor.

The Smith chart is.

  • The central horizontal line.: Pure resistance component (reactance 0)

  • Above the center.: Inductive reactance

  • Below the center.: Capacitive reactance

Therefore

  • 'The impedance is around 50 ohms, but there is a slight capacitive shift.'.

  • 'A slight capacitive reactance remains'.


I sent out a CQ on FT8 at 3.573MHz between 6pm and 7pm Philippine time and received calls from many stations.
There are very few stations on Mindanao Island IOTA OC-130 that are on air on the 80m band, so it may be rare.
With autumn conditions in Japan, it looks like we'll be able to enjoy 3.5MHz for a while.
 
September 10, 2025.   September 13, 2025.