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Question About Antennas

07/08/2015 11:42 AM

Is a good transmitter antenna, a good receiver antenna also?

What do you think?

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#1

Re: Is a good transmitter antenna. good receiver antnna also

07/08/2015 11:49 AM

Yo mama too fat.

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#2

Re: Is a good transmitter antenna. good receiver antnna also

07/08/2015 11:51 AM

It depends. I can transmit and receive from 10hz to 160hz on one of my antennas but I could also build a receive only antenna that would receive better on a single frequency. So it depends on the frequency, the conditions, the "mode" FM, AM, CW etc., the location and the power of the transmitter, and the gain of the receiver. So it depends!

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#3

Re: Question About Antennas

07/08/2015 12:07 PM

An optical antenna or photo electric one?

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#17
In reply to #3

Re: Question About Antennas

07/08/2015 6:32 PM

I am looking for the general principle, along the wide spectrum of waves

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#4

Re: Question About Antennas

07/08/2015 12:16 PM

Try consulting the ARRL Handbook as was suggested in your last thread. Don't expect help from others until you start helping yourself first.

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#16
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Re: Question About Antennas

07/08/2015 6:30 PM

There are some points in the topics that are not written in books.

These guys are better than books.

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#19
In reply to #16

Re: Question About Antennas

07/08/2015 6:51 PM

If you are serious about antenna theory, which I doubt, get a copy of the ARRL handbook AND READ IT.

Nothing you hear from "these guys" will be better than what is written in the reference books.

I could tell you about the time when I used a VSWR matcher and a metal patio umbrella as an 11 meter antenna, but it would not be good advice.

And you would never understand how I could get away with it unless you read the book.

RTFB!

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#28
In reply to #19

Re: Question About Antennas

07/09/2015 12:13 PM

A metal closet pole + matcher + Viking Ranger = Television "checkerboard"+ Uncle Charlie visit.

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#23
In reply to #16

Re: Question About Antennas

07/09/2015 5:25 AM

As lyn said, read the reference material.

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#5

Re: Question About Antennas

07/08/2015 12:16 PM

For the same frequency the antenna gain will be the same, obviously.

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#6

Re: Question About Antennas

07/08/2015 12:32 PM

It depends on many unspecified parameters and conditions....but generally speaking, yes....It's called reciprocity...

"It is a fundamental property of antennas that the electrical characteristics of an antenna described in the next section, such as gain, radiation pattern, impedance,bandwidth, resonant frequency and polarization, are the same whether the antenna is transmitting or receiving.[13][14] For example, the "receiving pattern" (sensitivity as a function of direction) of an antenna when used for reception is identical to the radiation pattern of the antenna when it is driven and functions as a radiator. This is a consequence of the reciprocity theorem of electromagnetics.[14] Therefore in discussions of antenna properties no distinction is usually made between receiving and transmitting terminology, and the antenna can be viewed as either transmitting or receiving, whichever is more convenient.

A necessary condition for the aforementioned reciprocity property is that the materials in the antenna and transmission medium are linear and reciprocal. Reciprocal(or bilateral) means that the material has the same response to an electric current or magnetic field in one direction, as it has to the field or current in the opposite direction. Most materials used in antennas meet these conditions, but some microwave antennas use high-tech components such as isolators and circulators, made of nonreciprocal materials such as ferrite.[13][14] These can be used to give the antenna a different behavior on receiving than it has on transmitting,[13] which can be useful in applications like radar."

https://en.wikipedia.org/wiki/Antenna_%28radio%29

http://www.arrl.org/how-antennas-work

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#18
In reply to #6

Re: Question About Antennas

07/08/2015 6:33 PM

Nice one SE. Ty.

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#24
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Re: Question About Antennas

07/09/2015 7:26 AM

Isolators and circulators and filters and combiners and diplexors are part of the RF feed not the antenna.

Otherwise reciprocity rules.

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#25
In reply to #6

Re: Question About Antennas

07/09/2015 10:02 AM

I used to build circulators and isolators, and internally the reciprocity rules still apply. Both have three legs: 1 for transmission; 1 for antenna; one for reception. In an isolator, the transmission leg is terminated with an impedance matching resistor.

In any case, the device is passive, and the antenna leg can be substituted with either other leg and still used in much the same way.

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#7

Re: Question About Antennas

07/08/2015 1:07 PM

The gain of the antenna is fundamentally dependent on the wavelength. For maximum gain, the antenna length needs to be the same as the wavelength of the desired frequency (f) or λ = 1/(2pi*f)

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#8

Re: Question About Antennas

07/08/2015 1:48 PM

I never used aluminum foil on a rabbit ear transmitter antenna.

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#9

Re: Question About Antennas

07/08/2015 1:53 PM

Some good suggestions,....

I like to add, depends on the materials you used,...... but then again, I'm a novice..

Have you considered a Fractal antenna?

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#21
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Re: Question About Antennas

07/09/2015 2:10 AM

Yes, you're close to there :)

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#10

Re: Question About Antennas

07/08/2015 2:18 PM

What is the difference between an antenna and an aerial?

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#11
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Re: Question About Antennas

07/08/2015 4:05 PM

height...

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#13
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Re: Question About Antennas

07/08/2015 4:38 PM

Bless you....

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#12

Re: Question About Antennas

07/08/2015 4:36 PM

Only if it is a full wavelength.

If not, you could try a band aid.

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#14

Re: Question About Antennas

07/08/2015 4:45 PM

I experimented with two walkie talkies and walked until I couldn't hear anymore but I couldn't tell if it was the transmit or receive that quit first. The ducks I used protested loudly.

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#22
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Re: Question About Antennas

07/09/2015 5:23 AM

As kids we did the same thing.... To see how good our walkie talkies were..... At one point, we got pretty far away... By following a high fall line? And felt quite an accomplishment. Yes, as kids we were running lab experiments, and didn't even know it. Now a days, kids are devastated when their cell phones have no service.

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#27
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Re: Question About Antennas

07/09/2015 11:35 AM

Yep. The kids nowadays have to depend on "Skip" just to communicate with each other and since they aren't into exercise their communications are severely suffering.

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#31
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Re: Question About Antennas

07/12/2015 6:28 PM

Good to hear how kids did things back then (I'm 80). We experimented with chemistry, and electricity. Made some pretty good bombs. Today, you would be locked away as a terrorist. Just for your amusement, I used to buy dangerous chemicals in New York City, like Sulphuric and Nitrite acids and carry them on the subway to home. Ah, I miss the wonderful electronic parts stores that were on Cortland Street in NYC. I was one of those weird kids who spent the weekends in such places while everyone else was playing baseball or stickball. I bought my first HiFi amplifier, a Bogen model PH10 in 1956. I thing it only cost about $30, but that was half a weeks salary. I had a binaural (not stereo) tape recorder setup that blew my mind and I built a binaural parallel tracking turntable arm that played the then binaural records. Memories..

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#32
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Re: Question About Antennas

07/12/2015 8:12 PM

I did the same also with my older brothers chemistry set.... To the chagrin of my mom.

Broke my other older brothers radio he put together in his science club he belonged to in high school.

Now-a-days,.... Interesting how people think between the two different generations. People would question how I ever lived through it. Back then by Using and/or Breaking my older brothers stuff while today. While today, playing with toys that are so dangerous....

(2) years ago, I was vacationing in Amarillo, TX with my girl friend and her sister took use to an antique store on Route 66, there was a chemistry set where you could refine oil.... It was amazing.

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#15

Re: Question About Antennas

07/08/2015 4:58 PM

Yes, both deal with the coupling of electromagnetic waves to and from conducting media, like wire or coax.

Both transmission and reception are optimized by an antenna of the correct length - which is a function of the frequency of the transmission/reception and is usually a fraction of a wavelength, most commonly 1/4 or 1/2 wavelength, but off lengths can be less efficiently matched or tuned to the frequency by a tuner or matcher.

The most efficient coupling occurs with perfect impedance matching. Commonly a transmission line is 50 or 75 Ohms, with the antenna made to present the same impedance to the line and the transmitter/receiver made to have that same impedance.

Energy is transmitted from the transmitter to the line and to the antenna, and if nothing is reflected = optimal, as shown by the SWR Standing wave ratio

in receiving, you are catching radio waves on the antenna and conducting them to the

transmitter/receiver and if your SWR in 1 = maximum signal to the receiver input.

Transmitters(Tx) and receivers(Rx) are discrete pieces of equipment.

Tx usually deal with higher powers being emitted, Rx is very small powers being received. They often share the same antenna and line, with a duplexer or TR switch to separate the signals. Full duplex is like a telephone or face to face talk, you can both talk at once. Half duplex is like ship to shore radio, where you say "Over" for the other end to speak up. Often transmitters are hundreds of watts, and receivers are in microwatts, so care must be taken that the transmitted energy does not enter the Rx = causes desensitising. This is handled by duplexers, transmission offsets, etc = complex task.

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#20

Re: Question About Antennas

07/08/2015 7:36 PM

Never mind!You are a COMPLETE waste of time. <Just read your other[searching for a charitable term here] question>Don't buy the book, you can't eat it.

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#26

Re: Question About Antennas

07/09/2015 10:03 AM

Yes it is, but the reverse is not always true. For a transmitter you need to be aware of SRW.

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#29
In reply to #26

Re: Question About Antennas

07/09/2015 7:52 PM

Pray tell what is "SRW"? Is there any chance you mean "SWR" (Standing Wave Ratio)? That makes more sense to me.

Bill

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#30
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Re: Question About Antennas

07/09/2015 11:24 PM

You got it.

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