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Old 9th Aug 2014, 6:26 pm   #1
stevehertz
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Default Number of tuned circuits in a set

Just out interest, having noticed that the criteria was mentioned in a web site's specifications of sets, what does the number of tuned circuits tell one? For example a set's spec says it has 8 am and 13 fm tuned circuits. So does that mean that this set has a better performance than another otherwise similar set with 6 and 10 respectively? Or is it not that cut and dry, maybe depending on the actual tuned circuit design etc? What's with the amount of tuned circuits? More is better? - better sensitivity?
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Old 9th Aug 2014, 7:03 pm   #2
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Default Re: Number of tuned circuits in a set

You need to differentiate *where* these tuned-circuits are.

A typical medium/long-wave broadcast/entertainment radio will have one signal-frequency tuned-circuit [ahead of the frequency-changer] and then usually four IF tuned-circuits [between the mixer/IF-amp/detector].

That's just fine on medium/long-waves, for receiving AM broadcasts.

When you move to short-wave reception you need additional selectivity - first, ahead of the mixer [to cut down on 'image' signals] and secondly, in the IF stages to give better exclusion of 'adjacent channel' signals.

So a receiver optimised for short-wave 'communications' service may have three or four signal-frequency tuned-circuits [and two RF-amplifier stages], and six, or maybe even eight, intermediate-frequency tuned-circuits [with two or three IF-amplifier stages].
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Old 10th Aug 2014, 10:43 am   #3
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Default Re: Number of tuned circuits in a set

Quote:
Originally Posted by stevehertz View Post
Just out interest, having noticed that the criteria was mentioned in a web site's specifications of sets, what does the number of tuned circuits tell one?
In addition to G6Tanuki's comments above, not a lot! In an extreme case, yes, it is reasonable to say, for example, that six tuned circuits will be better that one. But things are rarely that simple. For example, if the set employs multiple frequency conversions or if the set is of a modern design, a good deal more information is required to assess the expected overall performance of that set. A block diagram of the set, illustrating where the various tuned circuits feature in the overall scheme of things, is really required.

Al.
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Old 11th Aug 2014, 8:13 am   #4
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Default Re: Number of tuned circuits in a set

This "benchmark" is useless. I have a Grundig 1060 "Zauberklang" (Magic Sound) that proudly proclaims to have "10 FM Kreise, 7 AM Kreise". I have to count every coil in the signal path (including LO) to come to these numbers. Ratio detector alone now has no less than three circuits. FM performance (ECC85 front end) is, as usual, crap due to only one preselector tuned circuit. I would say had it had 13 circuits limiting action in the IF would have been much better.

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Old 11th Aug 2014, 10:21 am   #5
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Default Re: Number of tuned circuits in a set

If it's the website I'm thinking of, it is rather a strange and not terribly useful choice of tabulation. It gives the impression of a non-technical (or not overly technical) person being instructed to compile it and stolidly ploughing through the brief- as if to produce a slightly geeky set of the "Top Trumps" cards that were all the rage when I was a kid and gave a somewhat abstract comparison between sports cars, locomotives, fighter planes etc.

Much more useful and informative to refer to the actual circuit diagrams for comparison- or seek guidance from someone who's actually used the stuff. And here is probably as good a place as many (though there's likely to be a degree of debate!).
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Old 11th Aug 2014, 11:43 am   #6
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Default Re: Number of tuned circuits in a set

Thanks guys. I'm getting the drift. These stats are probably less than meaningful then. I'm not in a position to, neither do I have the technical know-how, diagrams or desire to start comparing circuit diagrams though. So I'll probably use a bit of electronic engineers' common sense re what else I know about the set; era, cost, pedigree, market aimed at, etc etc to give me an idea of tuning 'goodness'.
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Old 11th Aug 2014, 12:02 pm   #7
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Arrow Re: Number of tuned circuits in a set

An alternative metric to try to ascertain the 'figure of merit' of any radio is to count the number of valves (or transistors - but, in this case, that is not very indicative) that it contains.

Al.
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Old 11th Aug 2014, 1:38 pm   #8
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Default Re: Number of tuned circuits in a set

I think I have used the website and it seems the number of tuned circuits is very literal. If the number is large -above 6 - it is not really very informative on its own.
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Old 11th Aug 2014, 2:15 pm   #9
turretslug
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Default Re: Number of tuned circuits in a set

I can think of two broadly similar professional single-conversion receivers, one of which has 14 tuned circuits at 455kHz, the other has "just" 6. Both are highly regarded and frequently closely compared.
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Old 13th Aug 2014, 2:17 pm   #10
Maarten
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Default Re: Number of tuned circuits in a set

Quote:
Originally Posted by turretslug View Post
If it's the website I'm thinking of, it is rather a strange and not terribly useful choice of tabulation. It gives the impression of a non-technical (or not overly technical) person being instructed to compile it and stolidly ploughing through the brief- as if to produce a slightly geeky set of the "Top Trumps" cards that were all the rage when I was a kid and gave a somewhat abstract comparison between sports cars, locomotives, fighter planes etc.
If it's the site I'm thinking of, there isn't one single person compiling this data but rather people submitting and people approving if it seems reasonable enough. However there are more ways than 1 to count the circuits, manufacturers probably didn't even agree on that and as was said, I don't think that metric really is that useful under all circumstances.
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