# How to calculate antenna lengths.

Discussion in 'Wireless & RF Design' started by Jason78, Jul 1, 2016.

1. ### Jason78 Thread Starter New Member

May 26, 2016
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If I have a humminbird sonar fish finder operating on 115 kHz / 0.115mhz .

I'm looking to expose the antenna on both reciever and transmitter .

Now my problem is how would I calculate the correct length of antenna on each device to get maximum range of reception ?

Is there anyone out there who could calculate the math on this or simplify how it's done accurately please ?

Any help with this would be great fully recieved as its burning my head out .

Jay ​

Mar 30, 2015
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3. ### Jason78 Thread Starter New Member

May 26, 2016
17
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Thank you dl324 I'm still abit confused by it I'm obviously missing something ?

Jay

4. ### BR-549 AAC Fanatic!

Sep 22, 2013
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An ultrasonic audio wave is not the same as a radio wave.

5. ### Jason78 Thread Starter New Member

May 26, 2016
17
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I'm confused by it all tbh br-549 . Wish I hadn't attempted the conversion .

I have converted both devices and exposed the antennas but I seem to of shortened the range rather than extending it

6. ### BR-549 AAC Fanatic!

Sep 22, 2013
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I am by no means an ultrasonic expert. An ultrasonic transducer (not a true antenna) is sorta like a speaker/microphone combination.

Only instead of creating pressure waves in air.......it produces pressure waves in water.

Sonar is just a high frequency audio transmitter and receiver.

Study sonar and ultrasonic transducers.

Jason78 likes this.
7. ### Papabravo Expert

Feb 24, 2006
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I'm guessing that ultrasonic sensors improve with increased area. Not sure about ultrasonic transmitters. Beyond the shadow of a doubt they are in no way related to radiowaves. If they were, the half-wave dipole length would be approximately 1300 Meters from end to end. Clearly an impractical system for your purposes.

8. ### Jason78 Thread Starter New Member

May 26, 2016
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Yes papabravo

Ideally it would be a wireless system I think a 1300 meter antenna wouldn't be practicle .

9. ### BR-549 AAC Fanatic!

Sep 22, 2013
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I believe the quality systems use arrays for both transmission and receiving.

10. ### dl324 AAC Fanatic!

Mar 30, 2015
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Why? IIRC, the Navy towed an antenna miles long behind submarines for some very low frequency application.

11. ### BR-549 AAC Fanatic!

Sep 22, 2013
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That's true. But I recall that was a radio antenna.....for around 10 khz or so. Very low rf frequency so to go thru the earth.

It wasn't for ultrasonics or for sonar.

Edit.....If I remember right, the receiving antenna for that setup was buried underground in Minnesota, 11 miles long.

Last edited: Jul 1, 2016
12. ### Jason78 Thread Starter New Member

May 26, 2016
17
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I take it it isn't as simple as getting the correct length antenna to receive further range on the system them ?

Sounds complicated all this .

13. ### dl324 AAC Fanatic!

Mar 30, 2015
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Waves are waves; they just vary in length...
The frequency was more like 70-300 Hz. They also had planes flying over the oceans trailing miles long antennas to communicate with submarines.

14. ### BR-549 AAC Fanatic!

Sep 22, 2013
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No sir. Waves are not waves.

Two waves. A matter wave, or gravity wave (sound, water, earthquake) and a radio (electric and magnetic) wave.

Different waves for different mediums. Media displacement vs electrical field displacement.

15. ### BR-549 AAC Fanatic!

Sep 22, 2013
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Jason, I don't know your background but, if you are truly wanting to understand these things, it won't cost you much.

You can purchase small microprocessor prototype boards (arduino, avr, etc) and ultrasonic sensors. These are cheap and have plenty of free example software.

With a little study of the software program, you can see how the operation of the transducer is done. And how the received data is interpreted.

Then using and modifying the same setup........you may control a very high powered transducer. OR even arrays of transducers.

Don't kill or injure any wildlife.

16. ### Jason78 Thread Starter New Member

May 26, 2016
17
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I have just been shopping online to do that very thing.

See if I can't take over the world

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17. ### dl324 AAC Fanatic!

Mar 30, 2015
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Somehow I knew you would carry it to an extreme.

You forgot to mention waves in water...

18. ### BR-549 AAC Fanatic!

Sep 22, 2013
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"extreme" shouldn't be used to describe a simple standard. Even though ANY standard is considered extreme today.

Oh...you forgot to read the word "water" in my post.

19. ### KL7AJ AAC Fanatic!

Nov 4, 2008
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Did you know the jury is still out on this? I worked with ELF quite a bit at HAARP, and one of the most intractible problems was determining if ELF/ULF transmissions were true far-field EM waves ore merely mutual inductance. The scale lengths are so great it's impossible to get valid measurements....i.e., to see if the field follows the inverse square law or not!

20. ### KL7AJ AAC Fanatic!

Nov 4, 2008
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P.S. I presume the salient point is infrasonic radio wave...which is in the audio frequency range, but electrical.