phl@druxy.UUCP (01/23/84)
Is there an "inacuracy" in the digital tuning dial or has technology given the nit-pickers another field in which to gather and contemplate how many fairies can dance on the head of a pin? I suggest you consider: 1. Digital dial indications of 101.05 and 101.15 are only about 0.05% re- moved from an indicated base frequency of 101.10 mhz. 2. The station might be broadcasting slightly off frequency. 3. The receiver might not have stabilized. My ICOM R70 requires several hours to settle down. Some people leave their receivers on continuously if they want true frequency stability. Even then the tuner will drift a few khz/hr. 4. Some people unknowingly tune their receivers slightly off frequency because they perceive a "sharper" signal. 5. Analog dials indicate the tuned frequency with an error of several percent depending on the design of the cursor, position of the operator (parallax), size of the dial and a host of other factors. If this relatively gross error never bothered you with an analog dial why sweat the digital? If the hundredths digit bothers you why not have a competent repairman disable it or cover it over with tape? It is, after all, superfluous when you employ your AFC circuitry. I hope no one takes this as a flame at Kirk's sincere question. What really gets my goat are the unscrupulous manufacturers who feed on the technophiles need for an ever increasing dose of bells and whistles and pander to it at an ever increasing price. - Phil Lavette, druxy!phl
karn@allegra.UUCP (01/24/84)
A few comments. FCC rules (at least as of the time I was active in FM broadcasting, which was 8 years ago) require an FM carrier frequency accuracy of +/- 2khz. (By comparison, TV is +/- 1 khz, even for UHF, and AM radio is +/- 20 hertz.) American FM channel assignments are ALL on odd 200 khz spacings. Maximum deviation is +/- 75 khz. This is fairly broad compared to most tuning errors, except that tight IF filters may cause distortion with even small amounts of mistuning, given the way that stations like to drive right up to the legal deviation limits. Digital tuning allows the use of crystal-referenced synthesizers, which are much more stable than conventional "VFOs" (continuous free-running oscillators). The state of the art now in synthesizers is to hit accuracies of a few hundred hertz right from power on. In fact, it ought to be cheaper to build synthesized tuners than "analog" types because the latter require more mechanical complexity and precision temperature compensated components. Even with good design, continuous tuning receivers such as those common on the HF bands are less stable even though they operate at lower frequencies. The only things which would keep me from buying a digital tuner are: 1. The possibility that the FCC would start assigning "split" frequency assignments on even 200 khz steps. 2. Direct connection to cable TV systems which may use oddball, imprecise channel assignments. 3. Listening to FM "pirates" just outside the normal channels. 4. Listening from low earth orbit where doppler shift is a problem :-) Other than that, I wouldn't worry about the choice too much. Phil