There has been a lot of discussion lately, much of it just plain incorrect, about the relationship between resonance and antenna efficiency. Many incorrectly claim that resonance has nothing to do with antenna efficiency at all, similarly others incorrectly claim that resonance is a direct indication of efficiency. Neither of these statements is true. The reality is that resonance does have a significant impact on how efficient your antenna is, but the relationship is highly non-linear and depends on many characteristics.

Below I have attached a chart hat plots out the total radiation resistance (R_r) vs the measured input resistance (R_in) of a dipole. Efficiency is just R_r/R_in. In other words an efficient antenna will have 100% of its resistance as radiation resistance, and R_in is **always** larger than R_r (since it is essentially ohmic resistance plus radiation resistance). When these two numbers differ significantly an antenna is inefficient. The source for the chart below is here and it gives much of the math if you want a deeper dive:

nptel.ac.in/content/storage2/c

What is important to note here is that at anti-resonance we see a **huge** R_in value and a small R_r value, this means an anti-resonant antenna will have very high losses. Keep in mind the graph is very hard to read for the values <0.5 in length because the resolution isnt high. But there is significant divergence there as well. Notice at ~5/8ths wavelength antenna would exhibit very significant internal ohmic losses due to heat.

#hamradio #rf #radio #ee #electronics #electricalrngineering @Electronics

Two 60's HF Transceivers. (80-10 meters, 100 watts output, CW/SSB) SB-101 and the HT-37

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My first ham radio setup.


The  R-599 receiver, T-599D transmitter & S-599 speaker. (If I'm not mistaken also the MC-50 desk mic)

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@ai6yrham@twitter.com but I also have these, which I love dearly despite having to set up the freq against a 25kHz oscillator and still drifts +/- 50hz over a few mins after an hour's warm-up...

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12月5日 日曜日 敦賀市の空
6時50分 気象情報
気温 6.7℃,北 6.4m/s
降水 0㎜,日照0分,湿度 65%
日曜日、FBにお過ごし下さい。

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Digi contest in progress.. going fine beaming 100 degrees right now. Time for a cup off coffee 😉

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YB7NUS/P, YB7KE/P, YD7MHZ/P operations on Laut Island OC-166 completed successfully, see you in the next operation with Sa-ijaan DXpedition Team

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お昼にふと見上げたマイアンテナ。寒くなると、なかなか屋根に登れなくて。冬の寒い時のアンテナ点検は?


test with antennas

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SDRplay comparison of 4 popular magnetic loop antennas
youtu.be/aky9sVS0rTU

view at youtube A fantastic comparison.

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1/2. 6m E season is well and truly alive in VK/ZL!

I only have a vertical normally but, thanks to Richard VK7ZBX I am borrowing a 5 element yagi as there has been a TON of US and Mexico stations working VK on 6m FT8, I’m hoping to join the action.

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おはようございます GM❗️
良い天気です☀️

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PJ2T in Curaçao is running with full force this weekend, in the biggest contest of the year: CQWW CW !

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