What makes a good FM tuner?

[Jay]

I want to buy an FM tuner (hopefully an NAD). When I look at a Denon FM tuner in a supermarket, I thought there must be nothing important in the box, why it is so expensive. So what are the important criteria here? If I bought it, I would surely upgrade the component and the circuit.

I can’t imagine the most important and expensive parts in a radio! Antenna? Variable condensator? (Trimmable) coils? Amplifying IC? Or simply the features? What I care about is the sound! Any idea?

[nania]

I've been reading alot on this very subject and may be able to help. The first two things you need to do is to determine if your broadcast area is relatively crowded and if your emphasis is on pulloing in stations or having good sound. Once you have the answers to those questions, I have some recommendations.

[peranders]

Originally posted by Jay
Variable condensator? (Trimmable) coils?

A variable capacitor has been replaced by capacitance diodes long time ago, 15-20 years...?

I wonder also if there is any need for a very good radio. In Sweden has the commercial stations AWFUL sound quality, compressed and very modulated. The state radio has only one channel with some fidelity. The other ones have also compressed dynamics but have decent modulation.

[Jay]

<B>Nania</B>,

Good sound is all I need, and only FM. I don’t think that a standard FM tuner may not be able to handle “crowded” stations to an acceptable degree. Or, I can always set the inductance, for example, to allow for my favorite stations to be pulled in, can’t I?

But, is there any parameter to reflect the capability above? If turning on the radio is the only way to find out this capability, I don’t think that the seller provides adequate antenna if available (Well, I guess this will be a big problem).

<B>Peranders</B>,

What is capacitance diode?? Whatever it is, I don’t think that a good variable condensator (I mean the one from metal housing) can be outperformed by… diodes??

With radio I can hear the most recent popular songs, which I can use as a reference to buy a CD. And a wide variation of music option. With my CDP, I can only feed one CD at a time. As far as I can remember, the radio signal quality is very good in my country. Especially at night.

[jwb]

Do you have terrestrial digital radio broadcasts in your region? Check out the Arcam tuners: T-61 for AM/FM and some other model for Eureka DAB.

[nania]

Jay

Or, I can always set the inductance, for example, to allow for my favorite stations to be pulled in, can’t I?

Short answer to this statement is: No! Depending on the nature of the tuning capacitor and whether the filters are inductors or Murata chips (more likely) your attempts to tweak a tuner will probably result in making it worse overall. Do you have a good spectrum analyzer available to you (you'll be working in RF you know)? Doing alignments in the IF on a good used piece and maybe some parts upgrades will result in a much better bang for buck than anything you can find for $2500 nowadays. I would say your best bet is to look into the used market. There is alot of very good undervalued product that looks real nice too. Don't look at anything with less than 4 FM tuning capacitors and stay away from boutique stuff. Oh, and moderators should probably move this thread to the Analogue section where I think it belongs.

[tvi]

A good souce of information on used tuners is at: <a href="http://www.fmtunerinfo.com/">Tuner Information Center</a> they also have a forum at <a href="http://groups.yahoo.com/group/fmtuners/">groups.yahoo.com/group/fmtuners/</a>

Hope this helps

Regards
James

[pinkmouse]

Originally posted by nania
Oh, and moderators should probably move this thread to the Analogue section where I think it belongs.

Your wish is my command

[planet10]

I don't know how they are today, but older Onkyo tuners are outstanding -- certainly have a leg up on the concurrent NADs (i've owned both).

And on another note, what are you typing to get this -- windows specific i'm guessing -- character that i'm guessing is supposed to be a single quote? (see pic)

dave

[EC8010]

A tuner has to handle a very large dynamic range from the strong signal of a nearby station to the weak signal of a far-off station. Moreover, it has to do this without distortion. The solution is to have automatic gain control that decreases the gain for the stronger station. However, when you tune to the weaker station, the gain must rise. If the RF selectivity of the front end is unable to reject the stronger station, the overload causes spurious harmonics of that station to appear. The tell-tale sign of this is that a poorer tuner appears to pick up more stations, when actually, it is picking up the same station up and down the dial. The VHF/FM broadcast band is too narrow for the fault to become apparent in this way, but the problem remains. The best way to improve RF selectivity is to have many ganged tuned circuits, but 5 gang variable capacitors are expensive, so varicap diodes began to be used in the 70s. Unfortunately, varicap diodes are not ideal capacitors, and it is difficult to make a tuner with varicap diodes that is as good as one with real air-spaced variable capacitors or variable inductors.

The other issue with overload/intermodulation is that the ideal gain device in the front end and IF strip should be capable of swinging large voltages without distortion.

The upshot of all this is that the final generation of valve tuners had very good RF performance. They aren't quite as quiet, and they don't have quite the sensitivity of a good modern tuner, but they are still very good. Their decoders are usually terrible, but there are aftermarket kits available.