MICRO ANTENNAS

[prateeksikka]

hi all!
isnt it the case that if we use FM or AM broadcasts at GHz frequencies we would be using an antenna of at the mosr few cms in length.
why dont we then go for radio broadcasts at these low frequencies?
any problem at high frequency communications?

 

[audioguru2]

The antenna on my new cell phone is only 1.5cm on the outside of its case, but might be a little longer inside it. Its max output is 1W at microwave frequencies.
There are millions (thousands?) of cell phone base station transmitters in my city but only a single radio station transmitter for each station, so the difference in range is huge.
AM broadcasts are picked-up by a little ferrite loop antenna and FM broadcasts by a little whip, work fine with good range and were invented long before communication by microwaves was possible.
I don't see any advantage to change broadcasts to microwave frequencies now.

 

[prateeksikka]

hi audioguru!
but consider the fact that height of antenna would be so small at these high frequencies.
carry an FM receiver in ur pocket.
By the way what is the loss at using microwaves for FM broadcast. only advantages i can see.
any disadvantages u can think of?

 

[audioguru2]

carry an FM receiver in ur pocket.

I carry my FM Walkman in my pocket. The cord to its earphones is its antenna.

what is the loss at using microwaves for FM broadcast. only advantages i can see.
any disadvantages u can think of?

I don't know much about the new microwave satellite music transmissions because they charge a high price for a subscription.

 

[ECET0purdue]

not 100% sure .......

ok it is transmitted at a feq say 94.7 fm  then when it reaches the radio there is a circuit inside which changes the feq to a lower feq so it can be played though speakers and head by the human ear.  Now the higher the feq means the circuit inside has to me more complex which cost more.  so why have a more complex circuit just to get an antenna little smaller?

cheers,
glen

 

[audioguru2]

Now the higher the freq means the circuit inside has to be more complex which costs more.

 

[ECET0purdue]

its called a discount.. that is why it was cheaper and you buy a plan which you pay for.. a radio is a one time cost ...if you could buy a cell phone and never have to pay to use it well then i bet they would cost a lot more...

btw....i once got a free phone too....along with that 3 yr contract for 84 dollars a month....

i rather own the IRS...
cheers
glen

 

[audioguru2]

Hi Glen,
My daughter gave me the free cell phone for my birthday present and also got a free one for herself by signing a 3 years contract for a low monthly price. We can make unlimited free local calls for 6 months, then after only evenings, weekends and calls to each other are free.
She got the good deal near the end of the month, near the end of the fiscal quarter and the salesman was very hungry for sales. ;D

 

[ECET0purdue]

was it nextel?  ...... i like them

 

[miloje984]

Hi,
you should consider a fine laser facing for the mobile  antenas,which works on a high frequencies.
Does anyone knows which modulation is used for the mobile networks?

 

[audioguru2]

Does anyone knows which modulation is used for the mobile networks?

My Nokia 6101 cell phone works on 4 frequency bands with a total of 299 channels, using GSM digital modulation. It supports e-mail and internet connection but my carrier company charges a fee for those services.

 

[prateeksikka]

hi audioguru!
the only thing i meant by my question was that in general what are the disadvantages of high frequency communications?
i.e we use some MHz range for FM and few kHz range for AM radios.
any reason for not going in GHz.
is noise effecting more at those high frequencies?
or something else?
;D

 

[audioguru2]

Hi Prateek,
I don't see any advantage to change broadcasts to microwave frequencies now.
I think I said that before.

 

[prateeksikka]

hi audioguru!
can u tell me in general is it more advantageous to have a high frequency communication system or a low frequency system.
Was there any logic behind assigning 88-108MHz as frequency for FM communication or was it just random?

 

[prateeksikka]

hi there all!
can anybody tell me the logic behind fixing up 88-108 MHz as range for FM?
and why not some other range?

 

[audioguru2]

I saw the history of FM broadcasting on the web. It started on a lower frequency then changed up to 88-108MHz.

 

[prateeksikka]

HI AUDIOGURU!
my original question was that why dont they further shift the frequency range up and further reduce antenna height.

 

[audioguru2]

my original question was that why dont they further shift the frequency range up and further reduce antenna height.

Because FM works fine at 100MHz and everyone's radio will need to be changed if the frequency was changed.

 

[prateeksikka]

ok.
now i understand.
But I have also studies that we are constantly moving towards hisher frequencies in communication.Anyway,what are the disadvantages of communication at say 10GHz than at say 100Hz?