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Tank Circuit
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How is PLL Tuning Able to Tune In Exactly to Station

10/21/2013 3:15 PM

The radios I have use PLL tuning which means they tune through spectrum in exact steps. So how can it tune in perfectly to a station whose transmitting frequency is out of line (so to speak) with its steps.

A pointer to any internet page illuminating this would be welcome.

Thanks.
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lyn
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#1

Re: How PLL tuning is able to tune in exactly to station.

10/21/2013 3:28 PM

Phase-locked loop - Wikipedia, the free encyclopedia
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Tank Circuit
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#2
In reply to #1

Re: How PLL tuning is able to tune in exactly to station.

10/21/2013 3:31 PM

Lyn could you point me to the bit in the wikipedia artical that speaks to my question. Thanks.
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PWSlack
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#6
In reply to #2

Re: How PLL tuning is able to tune in exactly to station.

10/22/2013 3:20 AM

Do feel free to add to the article once the clouds clear.

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Tank Circuit
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#3

Re: How PLL tuning is able to tune in exactly to station.

10/21/2013 3:41 PM

Thanks SolarEagle. So PLL gets the radio close and AFC or automatic gain gets it spot on.
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SolarEagle
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#4
In reply to #3

Re: How PLL tuning is able to tune in exactly to station.

10/21/2013 4:42 PM

10-4....

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Johny451
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#5
In reply to #3

Re: How PLL tuning is able to tune in exactly to station.

10/21/2013 10:41 PM

One issue here is the AFC range.

A PLL tunes through it's designed range in steps of it's "reference frequency" - often referred to as the "raster".

Simple PLLs designers set their reference freq. to the station offset, so for say AM stations in Australia that would be 9kHz - a 9kHz raster. There are better synthesizers out there that use "fractional" values and can tune to almost any frequency (within the VCOs range and these are becoming more common).

Then there's the AFC. Since the whole lot is Xtal locked, the AFC can only swing as far as the designers decide is reasonable to alow for Xtal aging - usually not far. (AFC is not done the same way for fractional synthesizers - the PLL is reprogrammed in small steps for AFC).

More information as to what the product is and how far off the normal raster you want to go would be helpful.

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Rixter
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#7

Re: How is PLL Tuning Able to Tune In Exactly to Station

10/22/2013 7:08 AM

The radios I have use PLL tuning which means they tune through spectrum in exact steps.

Actually, the exact steps are the starting point. A phase lock loop circuit detects the error between the tuning frequency and the station frequency and adjusts the tuning frequency accordingly.
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Andy Germany
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#8

Re: How is PLL Tuning Able to Tune In Exactly to Station

10/22/2013 7:18 AM

As far as I am aware, countries set the spacing and the allowed frequency that each transmitter uses. Furthermore, the transmitters today are frequency maintained to a very accurate degree.

The USA have slightly different standards for example and some equipment made for say the USA, may or may not get problems in Europe. Usually it will receive here, but maybe not exactly on frequency with possible sound degradation....

A lot of transmitters in the UK had to adjust their frequency to stay legal, many years ago. As I am sure many other countries did the same.... for example Radio 4 LW went from 200 to 198 KHz(?).....

From a post here it looks as though Australia also has its own standards....

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Tom_Consulting
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#9

Re: How is PLL Tuning Able to Tune In Exactly to Station

10/22/2013 8:18 AM

We don't need no steenkin' PLL!

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Tank Circuit
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#11
In reply to #9

Re: How is PLL Tuning Able to Tune In Exactly to Station

10/23/2013 8:33 AM

Dont understand. The rig pictured looks like one that uses digital tuning? Or is my humour module not working?
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Tom_Consulting
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#12
In reply to #11

Re: How is PLL Tuning Able to Tune In Exactly to Station

10/23/2013 8:47 AM

It's a hybrid... Just turn the dial until you hit the right frequency.

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Tank Circuit
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#10

Re: How is PLL Tuning Able to Tune In Exactly to Station

10/23/2013 8:28 AM

Thanks to all people posting answers. Plenty of food for thought. David
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Users who posted comments:

Andy Germany (1); Johny451 (1); lyn (1); PWSlack (1); Rixter (1); SolarEagle (1); Tank Circuit (4); Tom_Consulting (2)

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