BroadcastDoc wrote:That seems to be the rule with the FCC. We don't really care how you determine that you're compliant, as long as you can prove that you're compliant!
kcbooboo wrote:Do other people use GPSDOs as the reference for measuring AM TX frequencies, or does everybody try to pick up WWV on an HF receiver?
kcbooboo wrote:that's good enough for government work at any AM station.
Dale H. Cook wrote:It is good enough for "government work" (i.e., satisfying an EB inspector) only if you can demonstrate the counter's timebase traceability to NIST to the satisfaction of that inspector. I can demonstrate that traceability for my counters, but then, I have been an instrument collector for more than 30 years, and I have NIST traceable calibration equipment of a few types in my shop. None of it is up to the accuracy of today's calibration systems, but most of what I calibrate is older tubed instruments which I can calibrate to the manufacturer's specs. The standards that I use (such as standard cells) I in turn have calibrated and certified to NIST by a local cal lab. They charge me low rates because they enjoy seeing the older calibration gear that I own.
GregHahn wrote:Where is there anything in there about traceability? There is an appeal to WWV, et al, as a standard. But that's different than traceability, which implies a paper trail all the way back to WWV. That simply isn't there.
Deep Thought wrote:If you can't trace your instrument's calibration and precision back to a recognized standard than you are not in compliance.
Deep Thought wrote:Assuming you are asking a legitimate question and are not just here to argue, everyone knows that the FCC's readings are the ones which count, not yours, and if there is a discrepancy which shows the station is out of tolerance then you'd better be able to back up your readings with something more than your own arrogance. The key phrase here is "any method or procedure that has sufficient precision". If you can't trace your instrument's calibration and precision back to a recognized standard than you are not in compliance.
Dale H. Cook wrote:Deep Thought wrote:If you can't trace your instrument's calibration and precision back to a recognized standard than you are not in compliance.
Mark is old school, as am I. We are used to demonstrating compliance - that is how we were mentored when we started out in engineering decades ago. In the case of frequency measurements that means a paper trail to NIST (in my case, to WWVB).
Calibrating a counter to WWV is simple enough. The question is, how accurate is that calibration when you measure a transmitter's frequency days or weeks later? The underlying question is, what is the ageing rate of your counter's timebase?
kcbooboo wrote:I know the GPS system is maintained by the US Naval Observatory, and they probably reference NBS somehow
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