BOBAFETT The 40-meter end-fed antenna I built is very heavy, so it's impossible to straighten out. Even with a large arc in the middle, all eight bands have SWR below 1.5. As long as you can mount it at a sufficient distance from nearby objects, it will work fine.
BG6HFD BI7ALG The SWR should be around 2.5, which means it's still relatively close to the wall. The internal antenna can help compensate for this, but it will also reduce transmission efficiency. High background noise in urban areas is normal; the specific level depends on the SWR meter reading. Of course, weak reception can also be affected by poor propagation conditions, which may be caused by solar activity.
Gintoki BG6HFD Hey, could you please tell me how to calculate the specifications and loss characteristics of the feeder line when it's in a shortwave mode?
BG6HFD Gintoki The loss due to different specifications and manufacturer-produced cables may vary slightly. You can inquire about this when purchasing from a vendor.
BI7ALG BG6HFD The local ham radio operator told me that the proximity to the wall isn't a major factor, but I don't understand why the ground noise and standing waves are so high. Is this due to the recent propagation conditions? Should I fix the antenna to the top of the handrails instead? However, this would result in insufficient length, only allowing the coil to form a curved shape, making it impossible to straighten out.
BG6HFD BI7ALG The standing wave has nothing to do with the propagation situation; propagation refers to the ionosphere, and its effect is how far your signal can travel through the sky, as well as how far you can receive signals. My own experience tells me that if the antenna's feed point is too close to the wall or hangs down excessively, or if it's too close to the ground, it will increase the standing wave, and initially increases the 7 MHz standing wave. Of course, if the diagram shows a sloped installation, then the distance between the antenna's side and the wall may also be closer, so try installing it in a straight line along the handrail; it might work well.
BI7ALG BG6HFD The distance between the two handrails is exactly 20 meters. If the antenna is extended straight, both ends would be at the top of the handrail, so is it necessary to reserve 2 meters on each end to keep the antenna in a curved state? Would this affect the resonant frequency?
BI7ALG BG6HFD The distance between the two handrails is exactly 20 meters. If the antenna is extended straight, both ends would be at the top of the handrail, so is it necessary to reserve 2 meters on each end to keep the antenna in a curved state? Would this affect the resonant frequency?
BG6HFD BI7ALG Exactly 20 meters, I think insulating between the handrail and the antenna should be fine. There's no wall above the handrail, so let's try it.
BI7ALG BG6HFD The antenna and ladder are connected by a rope; is this considered insulated? If the antenna is attached to the ladder, will it affect the standing wave?
BG6HFD BI7ALG It seems like the order of connection should be ladder - rope - antenna - balun - rope - ladder, and this might have an impact.
BI7ALG BG6HFD Yes, according to the previous recommendations, horizontal dipole and standing wave issues cannot be resolved, so it should not be possible to transmit. I will ask the local ham radio group for help in the evening. I suggest that I use a V-shaped end-fed antenna, with 2 meters of rope left at each end of the coil, and pull the center point to the top of the opposite staircase. Is this solution feasible?
BG6HFD BI7ALG A V-shape is fine; I'm even considering whether to use a longer antenna to extend the frame or triangle, so that it can also be used in the low frequency range.😂
BI7ALG BG6HFD If possible, try the V-shaped configuration on the top floor tomorrow; we can deal with the standing wave issue later.
BI7ALG BG2EWI The previous evening, the setup had already been adjusted, with two ropes of 2.4 meters suspended at each end of the pendulum. One end was held up by a 4-meter bamboo pole, which was tightened using four sets of rope knots and a wind rope. Currently, the four frequency bands (7/14/21/28) exhibit minimal standing wave activity, and the noise level is relatively high due to its location on the outskirts of the city. We have successfully established communication with ham products from Hengyang, Xi'an, and Harbin.
BG2EWI BI7ALG That's great! My directional antenna, which is about two meters away from the building, also has a standing wave of around 0.1, and the performance is still good.
BG6HFD BI7ALG 恭喜！🎉 底噪大正常情况，小区干扰多，楼顶可能有航空灯的开关电源和电梯的组件，楼下也有电瓶车充电器等等干扰，这倒确实考验机器的性能了。当然要是59+20的噪音么，，，DX101来了都得跪
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