EMRFD Message Archive 13986

Message	Date	From	Subject
13986	2017-06-09 12:47:01	mosaicmerc	VHF/FM broadcast question
Hi All: Somewhat OT, but does anyone know of the accuracy required from a commercial broadcast FM station? Is it any better than 1ppm etc? I am hoping to use it as a reference to calibrate 10Mhz OXCO modules. I happen to have a 100Mhz station nearby.
13988	2017-06-09 13:37:48	Andy	Re: VHF/FM broadcast question
mosaicmerc@yahoo.com wrote: Somewhat OT, but does anyone know of the accuracy required from a commercial broadcast FM station? Assuming you're in the USA ... It used to be (and I think still is) +/- 2000 Hz.  So, that's about +/- 20 PPM. Is it any better than 1ppm etc? No. But the last time I worked in broadcasting (= decades ago), we had just bought a new FM exciter, with a non-ovenized XTAL oscillator, which appeared to be stable to better than 1ppm in day-to-day operation in a transmitter building with no A/C and wide ambient temperature excursions.  I was impressed!  It was an order of magnitude better than the ovenized oscillator it replaced. I am hoping to use it as a reference to calibrate 10Mhz OXCO modules. I happen to have a 100Mhz station nearby. I would not count on it. Technology has improved enough so that they might be within 1ppm.  Or they might not.  Even if the technology of modern XTAL cuts is such that their stability is that good, there is no incentive for the radio station to trim their frequency to that kind of absolute accuracy, and to keep it there as the XTAL ages, when their only requirement is +/-2kHz. Decades ago, the NBS used to have a document where they recommended using the TV color burst (3.58MHz) as a secondary frequency reference.  Whenever your local TV station was carrying a network broadcast (or was synced to the network), the color burst frequency was locked to the network's primary atomic clock.  All the TV networks had atomic clocks.  But then digital TBCs (time base correctors) appeared, and all that went out the window. Andy
13989	2017-06-09 14:52:06	Eamon Egan	Re: VHF/FM broadcast question
This NIST document specifies a 2kHz tolerance for FM broadcast in the US: http://tf.nist.gov/general/pdf/2111.pdf In Canada it's apparently 1kHz: https://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/sf01237.html#s6_2 Eamon
13990	2017-06-10 01:43:49	don	Re: VHF/FM broadcast question
No 100.0 MHz stations authorized in USA. 99.9 or 100.1, yes.
13991	2017-06-10 08:59:00	Todd F. Carney / ...	Re: VHF/FM broadcast question
WWV broadcasts exactly on 10MHz. Here's a link: https://www.nist.gov/pml/time-and-frequency-division/radio-stations/wwv 73, Todd K7TFC 73, Todd ------------------------------------------------------------------------------------ ​ K7TFC / Portland, Oregon, USA / ​CN85pl / UTC- ​8  (PST) ------------------------------------------------------------------------------------ On Fri, Jun 9, 2017 at 1:39 PM, d
13992	2017-06-10 18:59:47	AncelB	Re: VHF/FM broadcast question
Hmm, Denver to Port of Spain is over 5000Km. https://www.google.com/maps/dir/Denver,+Colorado/Port+of+Spain,+Trinidad+and+Tobago/@24.0773867,-101.4910669,4z/data=!3m1!4b1!4m13!4m12!1m5!1m1!1s0x876b80aa231f17cf:0x118ef4f8278a36d6!2m2!1d-104.990251!2d39.7392358!1m5!1m1!1s0x8c3607de174bc349:0xdddef653160d4285!2m2!1d-61.5019256!2d10.6549013