Are they any good? Has anyone built one? Circuit is pretty staight forward. Schematic can be found at http://www.users.bigpond.com/cool386/pcrx/pcrx.html. Just want to know how good it is from a reception and audio quality stand point. I've built a few simple regen sets, but i want something that performs better on an FM band.

JK,
The pulse counting (PCD)or pulse averaging (PAD)FM demod was quite good compared to the older ratio detectors, Foster-Seely discriminators, and special FM detector vacuum tubes. It made its commercial appearance in the early '70's, in high cost, premium FM receivers for audio home use. It was, as far as I know analog FM's first foray into a digital world. Government, military and NASA telemetry receivers used variations of the circuit somewhat earlier. Just prior to that era, the PLL demod. (phase locked loop)was quite popular, theoretically being able to track an FM signal into the noise region, and still produce quality audio, although noisy during a deep fade. There were several mfrs with their own variation of the same basic circuitry, integrated into chip form, with an input, an output, and a few timimg and decoupling components. The PLL was basically an analog circuit, with its inherent analog noise problems, whereas the PCD or PAD circuit had inherent noise rejection capabilities that only a digital circuit could produce. I haven't inspected the site you mentioned, but I was instrumental in an early 70's PAD design for a government project. It consisted of proven techniques/technology, in both discrete and integrated components. The PAD OR PCD is a demodulator only, and requires a high gain IF subsystem (80-100dB) and RF amplifier/tuning subsystem to complete a receiver. Today's receivers on a single chip contain some form of digital demodulation, IF sub-systems, RF amplification and tuning elements, with few outboard components.
marv nuce

:Are they any good? Has anyone built one? Circuit is pretty staight forward. Schematic can be found at http://www.users.bigpond.com/cool386/pcrx/pcrx.html. Just want to know how good it is from a reception and audio quality stand point. I've built a few simple regen sets, but i want something that performs better on an FM band.

JK,
Clarification!! Should have said "Low noise RF amplifier/tuner/converter subsystem to complete a receiver.
marv

:Are they any good? Has anyone built one? Circuit is pretty staight forward. Schematic can be found at http://www.users.bigpond.com/cool386/pcrx/pcrx.html. Just want to know how good it is from a reception and audio quality stand point. I've built a few simple regen sets, but i want something that performs better on an FM band.

I just wanted to make a note for the heck of it. The troubles I have had with anolog tuners for FM are drifting, especially with tubes, though many Zenith radios I have used didn't have this problem. However, most digitally tuned FM receivers, though they are able to lock onto a signal very well, terribly distort the treble frequencies. I have learned that I have very sensitive ears and can pick up a lot of things that others cannot, so I'm not sure that everyone will notice this. Sounds in the "crispy" high end region, however, will sound grainy and unnatural--such as symbols, various harmonics in instruments--I've noticed this to be especially true for pianos, and also for some voices. Anolog tuners bring in superb clarity at all frequency ranges unless of course the broadcast station is also using a digital system with a low bit rate. I do not know if all digital tuners use the systems that Marv was talking about, but I've noticed that if I pay close attention to the sound of most that I listen to, they sound rather poor for critical high fidelity listening.

Thomas

Such an anolog tuner that I am very satisfied with is one of the Pioneer SX series tuners--SX-440, SX-660, SX-990. (Each one corresponds to the total wattage available to the speakers (40, 60, and 90 watts). These tuners bring forth the richest and most satisfying sound even with the highest quality speakers that have the fullest range.

Thomas

Thomas,
I have to take exception to at least one of your comments. Digital tuning is not digital demodulation, although some of the techniques are similar. First of all, digital tuners usually have a synthesized local oscillator, whereas 100 discrete frequencies are digitally created from one or 2 stable (xtal) frequencies, but still appear at the converter/mixer stage as an analog waveform. Tuning is accomplished by variable capacitance diodes, and once again the dc biases required for tuning varicaps are digitally derived. The signal still travels thru the tuner amplifier stages in analog form to some type of digital demodulator. Today's technology with extremely high speed/high gain/low noise devices, allows direct demodulation at the RF frequency after selective tuning the desired channel/station, but I'm not aware of any mfrs designing such hardware. Your aural sensitivity
(crispy)to digital derived sound systems may be its ability to reproduce audio well beyond the human sound system. High end speaker systems, unavailable 10 years ago, can also add to the pain. Inherent in such a system, are frequency ranges, harmonics and products of those sounds, never before experienced by human ears. Truly dirty or distorted audio can be a product of poor design, inadequate filtering, room acoustics, over driving the speakers and many other issues. Next time, try a pair of high quality noise canceling headphones with your digital FM receiver.
marv

:I just wanted to make a note for the heck of it. The troubles I have had with anolog tuners for FM are drifting, especially with tubes, though many Zenith radios I have used didn't have this problem. However, most digitally tuned FM receivers, though they are able to lock onto a signal very well, terribly distort the treble frequencies. I have learned that I have very sensitive ears and can pick up a lot of things that others cannot, so I'm not sure that everyone will notice this. Sounds in the "crispy" high end region, however, will sound grainy and unnatural--such as symbols, various harmonics in instruments--I've noticed this to be especially true for pianos, and also for some voices. Anolog tuners bring in superb clarity at all frequency ranges unless of course the broadcast station is also using a digital system with a low bit rate. I do not know if all digital tuners use the systems that Marv was talking about, but I've noticed that if I pay close attention to the sound of most that I listen to, they sound rather poor for critical high fidelity listening.
:
:Thomas

You know, I think the problem is mostly with factory equipped auto radios. On the rare occasion that I have come across a good digitally tuned home receiver, the audio was quite agreeable. Most factory equipped digital auto radios, however, are the ones that I find the cymbals a bit to crispy with. Honda radios are alright. Volkswagen radios make me cringe as well as Ford. GM is okay. About the best radio I've heard so far was either in a new Chrysler (clarity, not power) or in a Lexus.

T.D.

Thomas,
Room acoustics plays a big role in autos too, with the larger vehicles being easier to apply basic sound pressure dynamics. All that plastic can have dissastrous consequences, but the plush/soft interiors can be equally bothersome. My '02 Dodge Ram has AM/FM/Cassette, but no CD. Sounds good to me on those rare occassions when its powered. Mostly I prefer listening to silence, or the mellow purr of a well tuned V8. On my most recent road trip, tried to find powerful clear channel AM stations playing oldies or talk, but with little success. Does clear channel of yesteryear still exist, or is Nostalgia lost forever? I thought my AM had gone south, until I experienced the same problem with my restoration radios, having much longer antennae.
marv

:You know, I think the problem is mostly with factory equipped auto radios. On the rare occasion that I have come across a good digitally tuned home receiver, the audio was quite agreeable. Most factory equipped digital auto radios, however, are the ones that I find the cymbals a bit to crispy with. Honda radios are alright. Volkswagen radios make me cringe as well as Ford. GM is okay. About the best radio I've heard so far was either in a new Chrysler (clarity, not power) or in a Lexus.
:
:T.D.