Gang specifications used in FM receiver.

[electronics_shamim]

Sirs,

Can any one tell me the Gang parameters required for in the FM receiver set. Can a AM/SW Radio set Gang be used in FM receiver set? Understand AM/SW gang has three terminals. 1st is meant for AM Antenna, 2nd (middle one) ground, 3rd one meant for AM Oscillator.

Any idea on this pls let me know?

regards,
Shamim
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[audioguru2]

Hi Shamim,
Are you talking about a radio's ganged tuning capacitor?

How many gangs depends on the quality of the radio.
A good radio has an input tuned circuit, another tuned circuit following its RF amplifier and a 3rd tuned circuit for its RF oscillator.

A cheap radio has only 1 or 2 tuned circuits.

An AM radio at 1MHz uses a tuning capacitance up to 365pF.
A SW radio at about 20MHz uses a tuning capacitance up to about 65pF.
An FM radio at 100MHz uses a tuning capacitance up to 35pF.

 

[electronics_shamim]

Dear Audioguru,

Yes, Sir. I am talking about the tuned ganged capacitor which you have clarified clearly which is 35 pf for 100 MHZ for FM requirement. I was also really expecting reply from you, which I got.

Nowhere in the gang cap. there is any mention about pf. how can we know it is of which type? However, some gang caps. have 4-adjustable nuts on top of it, what are they used for? Is it trimmer (antenna & oscillator)?

Thanks for the same.

Regards,
Shamim_India.

 

[audioguru2]

I don't think ganged tuning capacitors for making radios are sold anymore. If they were then their datasheet would say the pF of them.

The nuts or small screws on a ganged tuning capacitor is to calibrate the frequency and to align their tracking.

 

[walid1]

Hi shamim
in addition to what guru said, look at the following link:
http://www.mikroe.com/en/books/rrbook/chapter3/chapter3b.htm
hope it help u