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Antenna Bandwidth

05/29/2016 1:53 AM

If an element is at a center resonant frequency, it will show a negative gain gradient as one moves off its resonant frequency, is this 'area under the curve' broadened with the diameter of the element? ie assume I somehow have a gain of 10dB at its resonance with a 1/8" D element, and drop 5dB's as I move up or down frequency from it's resonance, will I have a slower decrease of gain over change of frequency?

Thanks

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#1

Re: antenna bandwidth

05/29/2016 7:17 AM
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#2

Re: Antenna Bandwidth

05/29/2016 2:07 PM

I think you would have to test this in actual operation...and I think some corrections in length and spacing would be necessary...I don't think the gain would be effected much, but the larger diameter might increase the frequency...

http://www.eham.net/ehamforum/smf/index.php?topic=103611.0;wap2

http://www.digikey.com/en/articles/techzone/2011/mar/understanding-antenna-specifications-and-operation

http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6905785

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#3
In reply to #2

Re: Antenna Bandwidth

05/29/2016 2:53 PM

I think the frequency will decrease.

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#6
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Re: Antenna Bandwidth

05/29/2016 6:42 PM

A yes, as written you are correct, I think I meant frequency resonance...

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#16
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Re: Antenna Bandwidth

05/30/2016 9:19 PM

In my case down is good in that I'm thinking of ULF/ELF and don't have Hectars to rig a dipole across. I DO however have a tin barn so can fab a very low impedance coax from pipe and a baulan if necessary.

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#18
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Re: Antenna Bandwidth

05/31/2016 8:42 AM

Consider horizontal loops...I have one that's 540ft long. Check this out...

http://www.k5rcd.org/hor%20loop%20instruct.htm

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#19
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Re: Antenna Bandwidth

05/31/2016 11:11 AM

Are you trying to transmit also?? Your barn will be a fine top-hat capacitor but a very poor radiator, the balun is only there for impedance matching to the transmitter final amp.

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#20
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Re: Antenna Bandwidth

06/10/2016 10:07 PM

I don't plan on transmitting on ULF or ELF, just nosing around, The Gov is doing things there. The barn roof would make a great counterpoise for a vertical, I guess it would have a very low Q but will resonate at some low frequency and provide a better receiving antenna than anything rationally else. Gawd knows what it's impedance might be.

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#21
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Re: Antenna Bandwidth

06/13/2016 12:10 PM

All of your posts refer to parameters required for RF transmission, not reception. You do realize that a full wavelength VLF antenna would be about 60 miles long, anything shorter is a highly engineered compromise!

VLF receivers, on the other hand, use high gain, high impedance, highly filtered circuitry to compensate for the tiny amount of RF energy picked up by a 10-60ft long antenna. If you're handy with a soldering iron you can try this circuit.

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#4

Re: Antenna Bandwidth

05/29/2016 3:47 PM

A dipole antenna resonant bandwidth is increased if you increase the diameter. A biconical antenna is a dipole that has been "fattened" to increase its bandwidth.

http://www.schwarzbeck.de/en/antennas/biconical-antennas.html

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#5
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Re: Antenna Bandwidth

05/29/2016 4:12 PM

"at its resonance with a 1/8" D element". Not antenna.

I could be wrong here.

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#7
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Re: Antenna Bandwidth

05/29/2016 6:48 PM

Since the title is "Antenna Bandwidth", and he called it an element, I am assuming he is referring to elements of a Yagi antenna. I could be wrong also.

See: http://www.hamuniverse.com/yagibasics.html

"The design goal is to have the reactance at the center design frequency of the Yagi = (0),,, (j + 0).

The impedance matching device will now operate at it's optimum bandwidth. Wide element spacing, large element diameter, wide pattern bandwidth, and low "Q" matching systems will all add to a wider impedance bandwidth."

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#12
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Re: Antenna Bandwidth

05/30/2016 3:40 PM

true BUT the purpose of communication is to COMMUNICATE--which it did!

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#17
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Re: Antenna Bandwidth

05/30/2016 9:48 PM

Yes but, one of the problems with communication is the illusion that it has taken place.

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#8

Re: Antenna Bandwidth

05/29/2016 9:21 PM

You will find your answer in the last paragraph on page 30 of the link provided by Rixter.

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#9
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Re: Antenna Bandwidth

05/29/2016 10:04 PM
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#10

Re: Antenna Bandwidth

05/29/2016 10:29 PM

Yes. As a general rule of thumb, antenna bandwidth increases as the diameter of the elements increases.

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#11

Re: Antenna Bandwidth

05/30/2016 7:13 AM

Here is a lecture on antenna theory that will probably answer a lot of your questions.

Start with the basics,and work your way up,and your curiosity will spur you on to more and more knowledge.

30 minutes,but well worth the time.

https://www.youtube.com/watch?v=JYKEZATy4Fk

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#13
In reply to #11

Re: Antenna Bandwidth

05/30/2016 3:51 PM

SUPA! That's what I recall several decades ago when they'd just invented electronics and I went to school~~~ I'm thinking of a LARGE VLF/ULF antenna that maybe I can 'cheat' by using sheer size rather than miles of monopole,dipole/element(s).

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#14
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Re: Antenna Bandwidth

05/30/2016 7:16 PM

So you want to "cheat" the laws of physics so that you can listen to submerged submarines??? Good luck, if you want any type of traditional antenna you'll need an acre or two of vacant land and some very understanding neighbors. Even so about all you can "hear" is the highly encrypted FSK signals, the bandwidth is simply too low for any type of voice or real time video transmission.

You might try looking at various amateur radio sites such as this one that is dedicated to the hobby. The antennas aren't large or complicated, the "magic" is in the DSP s/w that takes the output of a simple receiver feeding a PC soundcard and decodes it. 73's

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#15
In reply to #13

Re: Antenna Bandwidth

05/30/2016 8:22 PM

Here is another link regarding all types of antennas,Fractal types are particularly interesting in terms of material and size reduction.

Page 104 is where the fractal section starts.

http://www.nabfastroad.org/reports/nabhighperformanceindoortvantennarpt.pdf

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HiTekRedNek (2); Johny451 (1); lyn (3); Michael Rogers (4); RAMConsult (4); Rixter (3); SolarEagle (3); Tom_Consulting (1)

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