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Your Antenna Is Tuned to the Wrong Frequency (Here's Why)

Telecom Training

26,594 views

Why is your antenna resonant on the wrong frequency? Learn how antenna reactance tells you whether your antenna is electrically too long or too short, and how to use your antenna analyzer to make the correct adjustment.

Many amateur radio operators know how to measure SWR, but aren't sure what the reactance (X) reading is really telling them. In this video, you'll learn how to interpret positive and negative reactance, why an antenna's resonant frequency shifts after installation, and how an antenna analyzer removes the guesswork from antenna tuning.

We'll cover:
• Why resonance doesn't always occur where you designed it
• Inductive and capacitive reactance explained in simple terms
• How to determine if your antenna is too long or too short
• Why nearby objects, antenna height, wire diameter, and installation affect resonance
• How to use an antenna analyzer to make informed tuning adjustments instead of guessing

Whether you're building a dipole, vertical, end-fed antenna, or another HF antenna, understanding reactance will help you tune your antenna more accurately and more efficiently.

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Thanks for watching!

Trevor
Telecom Training

#HamRadio #AntennaAnalyzer #AntennaTuning #Reactance
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Learn more about Telecommunications! Get my ebook "Telecommunications Simplified" here: https://amzn.to/3WsNpbF

20 Comments

@UnrulyGrandmother 3 days ago

This was very helpful! Thank you.

@richardmorgan8027 1 month ago

THANK YOU FOR A VERY WELL PUT EXPLANATION. BEEN HAM 65 YEARS. STILL.HAVE DIFFICULTY MAKING NEW (AND MANY OLD. GUYS) UNDERSTAND.. GOOD JOB.

@mscir 2 months ago

Great video class, thank you. Very clear and thorough.

@rudiwiedemann8173 1 month ago

DO NOT CUT! Just fold back the excess amount and either twist or tie them together onto themselves. Then you can always loosen the loop to lengthen if you want a lower resonant frequency. Antennas folded back on themselves act as shorter antennas by a bit less than the folded-back length.

@hellominions1604 1 month ago

Bsst explanation I have come across. Saved last diagram to my knowledge base for reference. 👍

@wherenowhow6037 1 month ago

An excellent tutorial. Thank you very much for your work and keep them coming please. 👍

@mervingcamille8834 1 month ago

Those are really good educational videos. So therefore next time I measure my antenna, I'll read the reactance and inductance as well... Nanovna

@khimroy3958 2 months ago

Thanks you teacher 👍👽📡🤖

@kevmscott 1 month ago

No mention of the length of the Coax feeding the antenna?

@MirlitronOne 2 months ago

Some mention of "velocity factor" might not have gone amiss...

@bill-2018 2 months ago

Remember: Low (SWR) is Long.
Don't forget it will very likely change as you raise the aerial.
Near enough is close enough anyway as we move about the band so it will change.
G4GHB.

@Jvan-j7x 1 month ago

👏

@yclept9 2 months ago

Want 14.2 got 13.8 the new length is (current length) * 13.8 / 14.2

@igorlaguta9146 1 month ago

Все это верно если анализатор подключить фидером длиной кратной полуволне рабочей частоты.

@TexasHamOperator 1 month ago (edited)

For HF amateur use: It is close enough.
Just use an outboard, high-quality antenna tuner, and all will be fine.
That slight bit of mismatch is irrelevant. And unless you're using really poor, lossy feedline, it will not make a noticeable difference.
All of your TX power will still get to the antenna (excepting the tiny amount lost in the feedline).

@charleswoods2996 2 months ago

I would build a dipole with telescoping steel whips, that way, if something is too long we can easily shorten it, and, if we need to lengthen it, we can. Because, when you cut wire, and it comes out your antenna is too short, I would think it would be difficult to lengthen it !
KD8EFQ

@Strannik7 1 month ago (edited)

У меня так же на 20м получилось. При этом на 15м в резонансе в широком диапазоне. Обе антены на одном кабеле и выполнены как инвертер ви. Послушаем, почему?

@kd5you1 1 month ago

Whenever I make an antenna, I measure the lengths by using the 468/f formula, and then I add a couple of feet of extra wire to each end. I run each wire end through an insulator and back onto itself. I secure the wire temporarily by using a bolt, wingnut and two washers. That way, I can loosen the wingnut and make the "balun to insulator" length shorter. Once I get my antenna's resonant point where I want it, I make it permanent by using a cable crimp. The excess is cut off except in the case I need a pigtail for making a longer antenna. 73 KD5YOU

@Pioneer936 2 months ago (edited)

I find it interesting that you state that when the reactances cancel each other out the antenna is tuned to resonance but when an antenna tuner does it you said in another video its not tuned ,a contradiction somewhere there or lack of understanding?

@DonzOzzo 2 months ago

If its too low, you need to lengthen it? I maybe missed something but you're talking about frequency or impedance.

I must need some Vitamin B to concentrate better. Lol