It's finally done after about ten days! Posting to commemorate ( )
I obtained my A license on September 13th, and the callsign I remember is 16. After that, I was active in the Zhenjiang and Nanjing areas. The equipment I have registered is a new QuanSheng UV-K6 and an old TheeTong TH-UV88 that I already owned. The original antennas were not very effective, so I paired the K6 with a QS-771 antenna to reach relays in the Nanjing province at 50km, but I still felt something was missing. I have always preferred to tinker myself, and there are many DIY antenna tutorials online. This led me to consider building my own Yagi antenna.
On September 27th, I received the nanovna (it's best to pair it with an antenna), and I planned to build a dual-element antenna. However, I realized that beginners should start with a single-element antenna first. After two days of research, I studied the Moksen-Yagi and KG0ZZ's UV Yagi antennas, and finally chose the design by KG0ZZ because it offers a larger bandwidth.
However, I made several significant mistakes that led to the failure of the project, including but not limited to: using 4mm stainless steel as the oscillator (which could not be cut or trimmed), using screws to fix the oscillator (which was non-removable and adjustable spacing was impossible), and a loose mounting system (the active oscillator was unstable). I have deleted the photos of the related processes, leaving only one photo of the final failed product for reference.
(I'm so busy with National Day preparations that I downloaded KG0ZZ's tutorial and video from archive.org, but the translation work is still ongoing.)
Finally, I realized what to do. I started making a seven-element Yagi antenna with a U-shaped section, using the remaining copper wire (approximately 2mm) from my home renovation project. My dimensions were based on the U-section of the previous UV dual-segment antenna. The first step was to cut out the radiator.
The cut piece is curved; it can be placed on a flat surface and rolled to find the point of curvature, then manually straightened.
Photo of the oscillator
Find the center line
Secure with strapping. The main support beam is a stainless steel wire used for fixing, and sandpaper should be used to prevent it from cutting hands.
Then there's the task of soldering the feed lines, but as you can see, the length I've stripped out is still a bit short.
After welding, I obtained a very good dipole antenna (fog).
The assembled unit was tested, and the resonant frequency was higher than expected. As a result, the insulation was removed, the spacing adjusted, and the coil was trimmed (thankfully, it wasn't glued in place). It performed effectively in practice, but not significantly so. According to feedback, it seemed somewhat intermittent.
At this point, I had already discovered that my standing wave pattern was W-shaped, with a peak around 435, but the valleys were low on both sides. Initially, I thought it might be due to a shortened active oscillator, so I replaced it with a new one, but it didn't work. I tried another one, and it still didn't work.
Later, I consulted with Qwen (artificial intelligence), and it told me that the impedance mismatch was likely the cause. When I checked the Smith chart, it did indeed show a problem, but I didn't have any capacitors on hand, so I had to try using a bnc adapter to match it.
(Actually, the AI also told me that your active antenna is a bit short, but your excessively long reflector unit compensates for this... All I can say is that you need to pay attention to the proportions when trimming the antenna.)
Previous frame image
Also, match the hair clip.
It was very lucky that I managed to get a match on the first try, and the standing wave also came down successfully. The lowest value achieved was 435, which can reach 1.03. Let's try it out again.
The performance was good; the Jianghai Gate repeater in Zhenjiang ranked seventh among the amateur radio repeaters in Nanjing Province, with a direct distance of approximately 55 km.
This is a general overview of my construction process. I didn't include diagrams because I lacked experience and didn't want to mislead anyone (primarily because I wasn't near the antenna). Adjusting the VSWR has given me some valuable experience, so next time I will try a Moksen-Yagi antenna.
This is BG4QBF, who always lags behind me in qbg. I wish you all the best (without qbg).
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