[upl-image-preview uuid=2dd08e71-5b29-443b-8462-ed3cb82fecee url=https://storage.hamcq.cn/2025-08-27/1756274025-485157-2dd08e71-5b29-443b-8462-ed3cb82fecee.png alt={TEXT?}] [upl-image-preview uuid=a486b31d-2c58-4698-b5d3-8fd74e96f855 url=https://storage.hamcq.cn/2025-08-27/1756274025-615038-a486b31d-2c58-4698-b5d3-8fd74e96f855.png alt={TEXT?}] 首先从天线的方向图上来看，达到了设计要求的，最大增益有9.59dBi，再中轴线上。 [upl-image-preview uuid=e5e7dd4e-d119-492b-9abb-23909bed29fc url=https://storage.hamcq.cn/2025-08-27/1756274025-30027-s11.png alt={TEXT?}] [upl-image-preview uuid=280350a1-506b-4c6d-a2a9-4ba8bdd4d618 url=https://storage.hamcq.cn/2025-08-27/1756274025-296555-vswr.png alt={TEXT?}] 再看端口，在144-146MHz范围内S11都在-20dB一下，驻波比在1.2以下。因此这个八木不需要考虑阻抗匹配的问题，直接接上就行。 [upl-image-preview uuid=60abb804-6785-448e-8042-0dfa033b4335 url=https://storage.hamcq.cn/2025-08-27/1756274065-715139-60abb804-6785-448e-8042-0dfa033b4335.png alt={TEXT?}] 最后附上尺寸图，使用4mm直径的铜管。欢迎大家交流指正！！

[upl-image-preview uuid=0fc234e8-2ea0-4ea9-ae61-4fd1c22f3d3e url=https://storage.hamcq.cn/2025-08-27/1756283102-819171-3cny.png alt={TEXT?}] [upl-image-preview uuid=5f3ebc64-5e48-4255-a2da-14c6e24fa3d5 url=https://storage.hamcq.cn/2025-08-27/1756283102-399864-3cny.png alt={TEXT?}] [upl-image-preview uuid=fdab757a-9afd-428e-a7ea-5e5f98a87247 url=https://storage.hamcq.cn/2025-08-27/1756283225-623352-fdab757a-9afd-428e-a7ea-5e5f98a87247.png alt={TEXT?}] 去掉后端的两个引向器，有源振子加长7mm后形成一个3单元八木，增益降到了7.4dBi，但带宽获得了比较大的提升。如果对于方向性要求没那么高的话，3单元貌似也够了。

振子的直径以及振子空心实心，对天线影响大吗

@"BA4SUA"#p76473 直径有影响，是否空心应该影响不大

@"BA4SUA"#p76473 仿真的结果上看，振子直径增大会使驻波比变大，从2mm变到6mm，驻波比变大0.02左右，可以忽略不计。其次，振子直径增大会使得天线的最大增益变大，从2mm变到6mm，增益变大0.12db，也可以忽略不计。振子实心和空心对天线性能和参数没有影响。总结一下，振子长度和间距两个参数会明显影响天线的性能，材质会比较明显的降低增益，粗细和空心的影响可以不考虑。

@"BG5FUM"#p76510 中心频率435，九单元，能不能帮我模拟一下比较优化的振子尺寸和间距

@"BA4SUA"#p76578 没问题啊，你把基本结构和尺寸发我吧，我微信号就是我的呼号

@"BG5FUM"#p76589 [upl-image-preview uuid=3d216613-fb47-45ec-a1aa-65fc375773f5 url=https://storage.hamcq.cn/2025-08-28/1756375708-698902-341881f7-b779-415e-9392-acfcb60dda8e.jpg alt={TEXT?}]

@"BA4SUA"#p76594 振子的材质和尺寸有了吗，还是按照理想状态进行仿真

@"BG5FUM"#p76601 材质是铁丝，晾衣架做的😀振子尺寸图中标了的，请帮我看看增益和驻波比，我没用天分测过。如果需要优化的，哪些尺寸该调整

@"BA4SUA"#p76602 OK，那我明天建个模型跑一下看看

I have simulated a 5-element Yagi antenna using CST, and the results look promising. I'd like to share it with everyone for discussion.

BI1NIZ

BG5FUM Well, after reading some reviews, it seems that HFSS is more complex, and CST doesn't require users to manually create air walls. MMANA-GAL is a simplified version, and the analysis models are also different. It assumes that all conductors are very thin lines relative to the wavelength, and then solves iteratively. Therefore, the iterative approach affects accuracy. Also, it becomes inaccurate when solving for frequencies above 1 GHz, mainly due to the iterative nature. Furthermore, it cannot handle waveguides or microstrip structures. The advantage of MMANA-GAL is its simplicity and intuitiveness, and everyone seems to agree that it's good.

BG5FUM

BI1NIZ I can handle all three major brands, haha. Use whichever one works best for you.

BA4ICQ

Hello, could you please simulate a 6-element Yagi antenna for the U band with a 73 kHz center frequency? Thanks.

BG5FUM

BA4ICQ Could you please draw a simple schematic diagram of the gamma arm and the main body of the antenna?

BA4ICQ

By the way, all four guide rods are 310mm long. The small dots in the diagram represent fixed holes; please disregard them. The hand position is at 165mm. Thank you.

BG5FUM

BA4ICQ
Since you didn't provide the power supply diagram, I proceeded with a standard approach, for example:

S11 as shown in the figure:

The two resonant frequencies are 420 MHz and 435 MHz, with their respective radiation patterns shown below:

The directional performance at 435 MHz is poor, while it's excellent at 420 MHz. It seems like you were looking for a device operating around 420 MHz.

BG5FUM

BA4ICQ Furthermore, adding a 2 pF capacitor to the output resulted in a shift of the resonant frequency to the left, and the larger the capacitance value, the lower the resonant frequency.

BG5FUM

BA4ICQ Starting from 9 AM and continuing until 3 PM, I simulated over 200 different parameter sets, but I never found one that satisfied me. I was unable to find a suitable way to power the gamma arm.

BA4ICQ

BG5FUM Thank you very much. I had to leave this morning because of something urgent, and I didn't have my computer with me.

I'm not sure if I can see clearly.

BA4ICQ

BG5FUM Thank you, original poster!

BG7MGW

I currently have a homemade Yagi antenna, could you simulate it for me? I'd like to compare it with the mmana antenna. In the diagram, 1 is the reflector, and 2 is the driven element. The materials are 8mm and 10mm aluminum tubing.

BG5FUM

BG7MGW What about the structure of the 10-unit connector?

BG5FUM

BA4ICQ Build the model according to your structure, as shown in the diagram.

BG7MGW

BG5FUM Yes, a 10-element Yagi antenna, with the feed point directly connected to the center of the amplifier, where the height in the diagram is the length of the amplifier in millimeters.

BG5FUM

BG7MGW Is the active transducer broken? What is the gap size? If it's not broken, what structure does it have?

BG5FUM

BG7MGW The structure is shown in the figure; the space between the centers of the active oscillators is 10mm.

The S11 curves for different spacings of the active antenna feed port show that there is almost no difference in directivity, and all values are above 13.6 dBi.

If you don't understand something, ask. Are you really planning to develop it? Is a multi-unit design necessary?

BA4ICQ

BG5FUM Thank you very much. 73, goodbye.

BG7MGW

BG5FUM It's not something I'm planning to build; it's already in use. How do you interpret this S-table, and what does the standing wave pattern look like?

BI1NIZ

The capacitor in this gamma-bar is adjustable, and this little structure is quite impressive...

BG5FUM

BI1NIZ This design is really clever; it includes an adjustable parameter, but I lack the necessary talent to fully utilize it.（NANOVNA）I don't think I'll be able to play this.
I followed your structure for @BA4ICQ We simulated the U6 Yagi antenna and found that there was only a slight change in the resonant frequency, which provides a significant way to adjust the resonant strength.

It's also possible that my fine-grained adjustments are not having the desired effect.

BA4ICQ

BI1NIZ 我的伽马臂做出来是这个样子的

BA4ICQ

BI1NIZ 外壁的铜管是如何实现在滑动的同时固定的？我现在的做法只能通过后期调整伽马臂的整体长度调整串入的电容量。

BG5FUM

BG7MGW

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