Bob, I would never think of using the 60 Hz power line to synchronize the clock on a mountaintop repeater, since the power gets interrupted on a fairly regular basis- usually due to the overhead lines touching due to wind galloping, or a tree branch falling across the lines. Once the power is interrupted, the time is in error and must be reset.
Cost-effectiveness in my book is based on not just the amount of time, energy, and materials it takes to incorporate the modification, but also whether it eliminates a trip to the site. Since most controllers that I am familiar with run on DC power, the modification to add a 60 Hz synchronizing signal is not a trivial exercise. The TAPR device I mentioned is a step in the right direction, since it replaces the BIOS clock oscillator with a much more accurate timebase. The use of GPS time synchronization is already used in cellular telephone and simulcast systems, and these GPS-disciplined oscillators are readily available on the surplus market. I use an HP GPS-disciplined time base to lock all of the equipment on my RF bench to a 10 MHz standard frequency, and I hope to do the same at each of my repeater sites. The Motorola MTR2000 repeater has a built-in clock that can be locked to a precise external frequency standard, and can trigger an outboard voice box to announce the time- but that is a back-burner project right now. I've already breadboarded a "time hack unit" which marries a WWV receiver to a tone decoder. At the beginning of each hour, WWV broadcasts 800 ms of a 1500 Hz tone. I have a simple tone detector set to key the repeater when it hears the tone, and to feed that tone to the audio input. Simplicity at this point is a disadvantage, since the tone detection delay and the keyup delay of the transmitter means that part of the tone won't get transmitted. To remedy that, I added a digital countdown unit that is set for 59 minutes 57 seconds. This countdown timer is reset by the tone detector once each hour, and its output keys the transmitter's PTT input. With this improvement, the transmitter is already keyed and waiting for the tone, which is broadcast immediately when received. The tone decoder's relay output keeps the PTT active until the tone goes away, and then releases it. The repeater controller detects the loss of PTT and then triggers the station ID. There are many ways to embellish this device, but simplicity and reliability are my goals. The RC-210 controller slipped my mind; when the poster wrote "or something like that" I thought of the RI-210. 73, Eric Lemmon WB6FLY -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Thursday, November 23, 2006 8:34 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder]Repeater Controller <snip> It would be more cost-effective to put an 120 VAC input on the controller for the purpose of picking off the 60 Hz reference. Ever wonder why your 50 year-old AC-powered clock keeps perfect time (between power failures, anyway)? Bob NO6B
