FM WAVE PROPAGATION

[audioguru2]

Hi Prateek,
I wouldn't say that higher frequencies have lower noise, just that they have less interference.

 

[Alun]

The interference gets higher at even higher frequencies.

At 22GHz resonance of water occures an 66GHz Oxygen resonates.

As we go up in frequency rain and eventually atmospheric moisture becomes a problem. Transmitters become increasingly difficult to build at any decent power level and above radiation above 300GHz the atmosphere is opaque to radaiton only to become transparent again in the mid-infrared region.

Having said that 100GHz is used in very high resolution radar and high speed data comunications.

There is a gap in the electormagnetic spectrum called far-infrared/submilimeter RF, between 300GHz and 30THz that's hard to study because lasers are hard to make wavelenghs longer than 10

 

[prateeksikka]

hi audioguru!
very less interference at very high frequencies.microscopic pocket antenna to transmit,what else do we desire?wat is the problem at such high frequencies?can we expect our radio services to run at few Ghz in near future?
prateek

 

[audioguru2]

Hi Prateek,
GM already has OnStar satellite help for their cars and next year (in a few months for cars) they will have your "satellite radio services running at a few GHz".

 

[Alun]

hi audioguru!
very less interference at very high frequencies

No as I've already said the interferance gets worse beyond a certain point in the RF spectrum because the molacules in the air resonate and noise from stars gets worse too.

If you want low noise transmision use the low noise window between 2 and 8GHz, but it gets a lot more noisy above 10GHz.

.microscopic pocket antenna to transmit,what else do we desire?wat is the problem at such high frequencies?

Transistors don't work at reasonable power levels at these frequencies so magnetrons and klystrons are used these are often very big and bulky.

can we expect our radio services to run at few Ghz in near future?

Many already do satalite TV works at around 5GHz.

 

[prateeksikka]

hi guys! i have heard that bandwidth is precious ! save it!
why is it the case when we are safely moving towards higher end of
spectrum(upto tera hz)?????
IS BANDWIDTH REALLY A THING TO PRESERVE????
PRATEEK

 

[Alun]

More bandwidth means more data per second.

Low THz frequencies aren't used but the higher 300THz near infrared is used in fibre optical comunications. This is way above the frequency that normal transistors work at so LEDs, lasers and photo diodes are used instead.

 

[prateeksikka]

hi all!
hi bandwidth and high frequency differ.
does working at high frequency ensure high bandwidth for the device?
what do we desire,high bandwidth or frequency?
prateek

 

[trigger]

no, high frequency do not mean high bandwidth.

It depends on the modulation, the coding , the filtering and the processing power on both transmitter and receiver (in case of digital communication).

I prefer high bandwidth more than high frequency.

 

[prateeksikka]

hi alun!
do you have any idea of chosing the 88-108 MHz as band
width of FM and not say 100-104Ghz?
dont you think that it will ensure much smaller height of antenna?
why dont we use that high frequencies?

 

[prateeksikka]

hi all
can anyone of you tell me why no TV has a grounding third pin,it always
has a 2 pin shoe connecting it to supply
prateek

 

[Alun]

TV's are doulble insulated a earth pin is only required when an appliance has a metal case.

Higer frequencies do mean more bandwidth,you can't modulate a 10KHz carrier with a 20KHz signal but you could modulate a 20MHz carrier with this 20KHz signal.


prateeksikka,
Yes high frequencies do mean short antennas but the antenna still needs to be on a very tall mast to achieve a long range. If you stand to a mountain you can see from 100s of miles and you can see a mountain from 100s miles away.

I don't mean to have a go but I've already answered your question about high frequencies, did you even bother to read my previous posts?
High frequencies are more prone to interferance and transistors and other components don't work very well at these frequencies, acept in infrared and optical band when LEDs and photo diodes work. - I'm not going to say this again.

 

[MP1]

I don't mean to have a go but I've already answered your question about high frequencies, did you even bother to read my previous posts?
High frequencies are more prone to interferance and transistors and other components don't work very well at these frequencies, acept in infrared and optical band when LEDs and photo diodes work. - I'm not going to say this again.

Alun,
You should calm down. You did not need to say that. You are flaming, which is against the agreement to use the forum.
For many members of this forum, English is not their first language. If they do not understand you, they will re-state the question. There is no cause to flame someone for this. In my opinion, the moderator of this forum should have deleted this post. Your sarcastic post would have been deleted in a forum I moderate soon after it appeared.

MP

 

[Alun]

OK, I'm sorry but I wish people would just say they don't understand me rather then just keep on asking me the same question over and over, - it's begining to annoy me.

 

[prateeksikka]

hey alun and MP i am sorry!
i read your earlier post which was pertaining to FM waves.
actually i had by mistake put the same question of TV at another place in the same site,which i forgot to check!
prateek

 

[prateeksikka]

HI ALL!
CAN ANYONE OF YOU TELL ME THAT WHY IS A RADIO BAND-BE IT F.M OR A.M BROKEN?I MEAN IT IS NEVER CONTINUOUS
I.E ALL FREQUENCIES ARE NOT PRESENT?
PRATEEK

 

[audioguru2]

Hi Prateek,
He, he. My FM transmitter goes that far? ;D
I am still tweaking my FM transmitter and frequently its output isn't modulated. It must be jamming radio station reception on FM radios with a "blank spot on the dial" all around me.
I've got RF coming out of my wing-wang. It is all over my preamp, 'scope and DMM. Everything I measure has strong RF on it, even me!

I don't know why your AM radio is jammed or broken. I'm not jamming it. I stay away from AM because it sounds lousy.

 

[prateeksikka]

hi audioguru!
sorry for it but i could not understand wat u said,i also fear u wrongly
interpreted my question.i meant that the frequency range 88-108 Mhz
for FM and 540-1600 kHz for AM.is not continuous.
i.e all frequencies are not used by am broadcast.some frequencies are used by other applications also
why is it so?
prateek

 

[audioguru2]

Hi Prateek,
I don't know why there are unused frequencies on your radio bands. My AM and FM dial is full of stations, some with different languages.
I am having diffuculty finding a frequency to test the little FM transmitter I built a few days ago.

 

[prateeksikka]

HI AUDIOGURU!
WHILE SEARCHING ON THE NET,I FOUND THAT SOME OF THE SO CALLED MISSING FREQUENCIES ARE RESERVED FOR USE BY OTHER APPLICATIONS LIKE MILITARY ETC
COMMENTS?
U TOO SEARCH FOR A POSSIBLE REASON AND DO TELL ME IF U GET IT!
PRATEEK