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but i am actually looking forward to learn things as i design the FM radio because FM radio is one of the most easiest application to start with.Can anybody help me in how to start with it
but i am actually looking forward to learn things as i design the FM radio because FM radio is one of the most easiest application to start with.Can anybody help me in how to start with it
What electronics experience do you have? Radio (RM, AM, or anything) is not really the easiest place to start. If you have a local ham club, though, that can help a lot if you are really interested in getting into radio electronics.
You have not filled in the location information in your User CP, however, so we do not know where you are and what clubs or resources might be available to you.
If you can tell us what electronics experience you have, perhaps we can suggest some good starting points for you.
It isn't clear if the OP wants to design a receiver, a transmitter or a transceiver.
I will assume a receiver, but the answer will be different if this is a wrong assumption. It would also be useful to know if the antenna must be attached to the receiver in some convenient way (for example, if it is a portable receiver) or if the antenna can be separate. Roff's link is a good one for a separate antenna. For an attached antenna, the most common variety is a short monopole made from telescoping sections. The length is important both electrically and for mechanical convenience, but a practical length is usually about 0.2 wavelengths, or about 60 cm. Most commonly the base of such an antenna is directly connected to a high impedance (greater than 100 ohms input Z) preamplifier which provides some gain. This direct connection eliminates the concern about impedance matching through a transmission line. Using a high impedance amp like this also allows you to vary the length of the antenna quite a lot and still get reasonable performance.
If we're talking about line-of-sight distances then antenna polarization might be an issue. As I understand it, if the transmit antenna is vertically polarized then the receive antenna should be for best reception. I can't say that I've ever measured or compared performance on VHF - just making note of what I've read.
If we're talking about line-of-sight distances then antenna polarization might be an issue. As I understand it, if the transmit antenna is vertically polarized then the receive antenna should be for best reception. I can't say that I've ever measured or compared performance on VHF - just making note of what I've read.
Basically vertical works best for cars (because it's easier to have a vertical aerial on a car, and it's omni-directional) and horizontal works best for home reception.
For this reason the UK generally uses slant polarisation on the transmitters, which gives decent reception on both types of reception aerials.
I'll have to ask my broadcast experts what they do here in the US. Typically television antennas are horizontally polarized - and even distance FM antennas are horizontal. Would be good information to have on hand.
I'll have to ask my broadcast experts what they do here in the US. Typically television antennas are horizontally polarized - and even distance FM antennas are horizontal. Would be good information to have on hand.
In the UK, TV aerials are (almost always) horizontal for main stations, and vertical for relay stations (there are a very few number of exceptions) - bear in mind we only use UHF for TV, the long obselete VHF TV was all vertically polarised (as far as I can remember, it's so long ago).
For FM, horizontal transmissions would tend to really affect car radio's, so it's probably slant transmission like here?.
It isn't clear if the OP wants to design a receiver, a transmitter or a transceiver.
I will assume a receiver, but the answer will be different if this is a wrong assumption. It would also be useful to know if the antenna must be attached to the receiver in some convenient way (for example, if it is a portable receiver) or if the antenna can be separate. Roff's link is a good one for a separate antenna. For an attached antenna, the most common variety is a short monopole made from telescoping sections. The length is important both electrically and for mechanical convenience, but a practical length is usually about 0.2 wavelengths, or about 60 cm. Most commonly the base of such an antenna is directly connected to a high impedance (greater than 100 ohms input Z) preamplifier which provides some gain. This direct connection eliminates the concern about impedance matching through a transmission line. Using a high impedance amp like this also allows you to vary the length of the antenna quite a lot and still get reasonable performance.
thank you Mr. RadioRon,your assumption is correct and it helped me to go further in my design.As I already mentioned I am trying to construct an FM radio and now I have attached a block diagram can anybody verify it for me please. Also if u have better design ideas,lemme know about it
That looks like a bog standard FM radio, apart from the 'audio voltage amplifier', that's not needed, the power amplifier provides the voltage gain as well.
Early 60's TV antennas (as far back as I can recall) were the same as they are now - and it may be that polarization was/is slant. In my amateur radio work there are some normal practices - 2 meter FM usually being vertical - 2 meter CW/SSB being horizontal. I suppose I could do some research to get a good answer but no time to do that right now. I do chat w a fellow amateur who is an engineer with local broadcasters in this area and if I get a good answe I'll post it. It's an interesting question.
I saw vertically polarized TV antennas in Britain and awfully coarse 405 lines.
I think their first TV system had everything wrong. Its vertical polarization reflected off tall buildings and made many ghosts. They had white as full AM power instead of black as in North America so AM interference was very obvious.
My cheap clock radio and Sony Walkman are overloaded by strong local stations. My home stereo and car radio are not overloaded because they have the input tuned to the station and have automatic-gain-control.
Don't make the FM radio that is sold for only $1.00. Its performance is lousy.
My new clock radio cost $1.25 and it sounds horrible. My souped-up clock radio is about 30 years old, sounds wonderful but its LED display has gradually dimmed until it can't be seen in daylight anymore. 30 years is about 262,800 hours. I didn't add a day for each leap year.
thank you Mr. RadioRon,your assumption is correct and it helped me to go further in my design.As I already mentioned I am trying to construct an FM radio and now I have attached a block diagram can anybody verify it for me please. Also if u have better design ideas,lemme know about it
Your block diagram is incomplete in my opinion because it doesn't show the filters that are critical to the function of a receiver. The most critical filter is the IF filter, found somewhere in the IF amplifier section. Many radios put this filter immediately following the first mixer while some include an additional amplifier between the mixer and the first IF filter. Can you guess why?
Other filters that are important include the de-emphasis filter which goes between the fm demodulator and any af amplifiers that follow it. It is also quite common to include a bandpass filter before the rf amplifier and between the rf amplifier and the mixer. Can you tell us why those are necessary?
I would like to know what frequencies you wish to receive with this receiver, can you tell us?
Your block diagram is incomplete in my opinion because it doesn't show the filters that are critical to the function of a receiver. The most critical filter is the IF filter, found somewhere in the IF amplifier section. Many radios put this filter immediately following the first mixer while some include an additional amplifier between the mixer and the first IF filter. Can you guess why?
Other filters that are important include the de-emphasis filter which goes between the fm demodulator and any af amplifiers that follow it. It is also quite common to include a bandpass filter before the rf amplifier and between the rf amplifier and the mixer. Can you tell us why those are necessary?
I would like to know what frequencies you wish to receive with this receiver, can you tell us?
Good point. I did not show it separately as the IF amp usually does this by saturating its output. This implies that you need a lot of gain in the IF amp, and this is generally true. It is not uncommon to have over 100 dB of IF gain so that the amplifier output limits on signals not far above the noise floor of the receiver.
I saw vertically polarized TV antennas in Britain and awfully coarse 405 lines.
I think their first TV system had everything wrong. Its vertical polarization reflected off tall buildings and made many ghosts. They had white as full AM power instead of black as in North America so AM interference was very obvious.
It was the worlds first TV system, so obviously had a few problems - just like the USA adopted 525 lines and NTSC for colour, so has the worlds poorest colour TV system. Early adopters usually get an inferior system, that's just the way it is.
Good point. I did not show it separately as the IF amp usually does this by saturating its output. This implies that you need a lot of gain in the IF amp, and this is generally true. It is not uncommon to have over 100 dB of IF gain so that the amplifier output limits on signals not far above the noise floor of the receiver.
I didn't think about that, that you could actually do that by over driving an amplifier, but that is true. I was referring to the diode limiter. I know you know that...lol.
Anyway, how are you doing radioRon? I got into building a PLL just a single loop so far. Well, I was looking at the frequency and all and said to myself. Hmmm...I need a new radio. So here I go. I got the 1st IF strip and rf amp and home made crystal filter & mixer done and in a metal can. Great performance so far. I'm on the second IF with mixer. Audioguru gave me some tips on good stuff to use in the audio so I got a few chips on the way.
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