Okay, I’ve been thinking (somewhat abstractly, since I have had relatively little free time lately) about what I eventually want my beacon transmitter to be. One of the issues with it is that I’d like it to be relatively autonomous and lower power: I’d like it to be able to run for weeks at a time without human intervention. I’d also like to use it for WSPR beacon transmissions, much as my original experimentation that I carried out. The trick for making a long term WSPR beacon though is time synchronization: WSPR transmissions begin on even numbered minutes, and must be accurate to a couple of seconds or so. The DS1307 I’ve been playing with only has that accuracy for a day or two: so I need something better. A few ideas leapt to mind:
- Temperature control the whole thing. I suspect this only postpones the problem for a period of a week or so, rather than curing it.
- Synchronize using a GPS. I’d only need to wake up for a few minutes every 12 hours or so to keep it going. Still, seems pretty high tech.
- Add a receiver for 10Mhz time signals. Nice, doable with technology I have on hand, but perhaps needlessly complicated and probably more expensive than…
- Using a WWVB integrated receiver. These are about $10, and have very low power consumption. Less homebrew, but perhaps a reasonable choice.
Digikey has ’em in stock for ~$10, falling to about $8 if you order 10.
You could also look at the impressive DS3232 series of chips, which add about a magnitude of accuracy. Only available in surface mount, but you don’t need an external xtal.
Mark, have you looked at Kees’ and John’s atomic clock kit #7?
http://www.qsl.net/k5bcq/Kits/Kits.html
With this antenna: http://www.aavso.org/simple-easy-build-sid-receiver I almost always have a good WWVB signal. The CMMR-6P-60’s ferrite antenna was not adequate inside my house.
The Atomic Clock kit is not available now, but Kees can provide the programmed chip and documentation, including artwork if you need an etched board. Source code may be available too.
You can use a CMMR-6P-60 receiver or probably get a WWVB pulse train out of a cheap radio controlled clock or even an AAVSO VLF gyrator: http://www.aavso.org/improved-gyrator-tuned-vlf-receiver
— Tom K9AC
Be careful with these CMMR receivers. They don’t toggle until several milliseconds after the correct time, even accounting for light time from the transmitter in Colorado. There is also a couple of milliseconds of jitter in this.
I saw this on a page directly comparing a GPS PPS signal with the output of this device, but I can’t find it again.
hi Mark-
This is slightly off of your homebrew clock topic..
In regards to pc clock accuracy, and as a long time user of “D4″(Dimension 4), I found that D4 was starting to conflict with my new Win7 pc (even after installing it and other ham radio apps directly to the c: drive). D4 began to lag by about 2 to 3 seconds- way too long for JT65 and EME (moon bounce) weak signal work.
A friend at Stanford University told me about “Chronos” (chronosatomic.com).
Chronos syncs to not one, but a dozen NIST servers. It has been working great for my applications. It is free, but does have a nag upgrade pop-up box every 5 bootups or so. When the popup shows-I just click on it + then close the page.
I temporarily relocated to Alaska (from the SFO area) for about 18 months or so, and the WWVH Kaui signal is fairly weak on 10mhz on my wire antenna. I have two “atomic clock rcvrs”, and they are unable to “see” the WWVB signal up here at 61 degrees latitude with their built-in loop antennas. hi
Thnx for your page here. I’ve been reading it for about 3 years now.
73, Eric KL/N6SPP _Anchorage
(WSJTing since the 2001 Leonids Meteor Shower)
[ n6spp/b 28.28 mhz xmtr: cm97 24/7]