Don, The "on-the-hour" tone is an 800 ms burst of 1500 Hz. I have built a PLL 1500 Hz tone detector into a Hamtronics WWV receiver, and it works fine- giving me a relay contact closure exactly on the hour. Unfortunately, that would only allow me to jam-set the minutes and seconds to zero, and would not correct an hour error- such as when DST starts and stops.
I considered dispensing with the voice time announcement completely, and just broadcast an hourly beep. The problem is that transmitters don't come up instantly, and most or all of the beep will be missed. My solution to that problem is to use the on-the-hour pulse to reset a simple countdown timer that closes a PTT relay at the end of a 59 minute 57 second delay. The countdown timer will key the transmitter shortly before the hour, ensuring that it is ready to pass the 1500 Hz beep exactly on the hour. As soon as the beep detector relay relaxes, PTT goes away, and the repeater will issue its identity message and return to idle mode. I'm still tinkering with this idea. The downside is that WWV reception varies with the time of day and propagation factors, and a decent antenna is required. 73, Eric Lemmon WB6FLY -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Don Kupferschmidt Sent: Sunday, November 11, 2007 5:43 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Dallas Semiconductor Real-Time Clock (Was RC-96 Controller Problem) Eric, I've been toying around with this idea for a couple of years - set the SCOM 7K clock to atomic standards. As you know, the 7K's are prone to drifting with their time of day clock. The idea is to have a stable WWV signal that "listen" to the top of the hour signal. I'm thinking that is a 1000 kHZ tone, but I could be wrong about that. If someone could build a circuit to decode the top of the hour signal from WWV, you could command the controller, through macros, to reset the clock. Shouldn't be all that difficult. The designers of the new SCOM controller recognized that problem earlier, and as I am told, have placed a new crystal / circuit in the time of day clock to address that problem in the 7330 line. With all of the 7K's out in the field, if a simple circuit could be made it would eliminate the drifting problem. Don, KD9PT ----- Original Message ----- From: "Eric Lemmon" <[EMAIL PROTECTED] <mailto:wb6fly%40verizon.net> > To: <Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> > Sent: Sunday, November 11, 2007 3:27 PM Subject: [Repeater-Builder] Dallas Semiconductor Real-Time Clock (Was RC-96 Controller Problem) > Mike and others, > > The Dallas Semiconductor "Nonvolatile Timekeeping RAM" found in many > popular > controllers, including the Link RLC-1 Plus, is Part Number DS1643-150. > The > 11-page datasheet can be downloaded here: > > <www.datasheetarchive.com/pdf/1235806.pdf> > > Notice that the "-150" indicates 150 ns access time. The replacement > device > offered by Dallas/Maxim has either 70 ns or 100 ns access time, and I have > no idea if the newer device will work properly where a 150 ns device was > used. > > On page 5 of the datasheet is a paragraph entitled "Internal Battery > Longevity" which states that the device can operate for 10 years in the > absence of VCC power. When powered as it would normally be in a typical > application, the note states that the lifetime can be as long as 20 years. > The battery is not accessible for replacement. > > I see that the guaranteed accuracy of the DS1643 clock is within +/- 1 > minute per month, and there is no capability to tweak the crystal to get > better accuracy. One of the Hams in my area is experimenting with a > scheme > to use a so-called atomic clock to jam-set the correct time once per day. > With regular synchronism to WWVB, the time announcements will normally be > no > more than a second off. Once he gets this idea working, perhaps I can get > him to write an article about it. I and many other "time-and-frequency > geeks" think that time announcements should be correct. > > 73, Eric Lemmon WB6FLY
