You should try it. --- On Fri, 3/25/11, n...@n5ge.com <n...@n5ge.com> wrote:
> From: n...@n5ge.com <n...@n5ge.com> > Subject: Re: [Elecraft] Installed K3EXREF > To: elecraft@mailman.qth.net > Date: Friday, March 25, 2011, 1:02 PM > > Glad you're going to give it a rest..... > > N5GE > > On Fri, 25 Mar 2011 09:45:31 -0700 (PDT), Wes Stewart > <n...@yahoo.com> > wrote: > > >I'm not picking on Paul, this is just a handy place to > reply. I'm going to say this one more time (the first time > was two years ago). > > > >I really don't understand all of the fuss about 1 Hz > accuracy when just changing the K3 Width and Shift controls > moves the frequency more than that and this is band > dependent. > > > >On ten-meters I can listen to a crystal-controlled > source and hear the beat note change as Shift and Width are > adjusted. > > > >Elecraft considers its frequency conversion scheme to > be proprietary but it's obvious that not all of the > oscillators are moving at the same rate. > > > >Wes N7WS > > > >--- On Sat, 3/19/11, Paul Christensen <w...@arrl.net> > wrote: > > > >> I installed it on Friday in about 30 > >> minutes, but I'm comfortable with my > >> way around the K3. I would think that most > users > >> could install it in about > >> an hour or less. Installation is actually very > simple > >> with very few parts > >> involved. K3EXREF came with an SMA connector and > SMA > >> to BNC between-series > >> adapter. > >> > >> Performance is exactly as promised by Elecraft. > >> Although K3EXREF will not > >> phase lock the K3 to the external frequency > source, I'm > >> finding that it > >> stays within 1 Hz on 20m when locked to CHU at > 14.670 > >> MHz. I'm also > >> finding that testing for zero-beat to WWV at 10 > MHz is not > >> a good idea in my > >> shack, and perhaps yours too. There are many 10 > MHz > >> signals being emitted > >> by nearby appliances, LAN routers, security > system, > >> Ethernet boards, etc. > >> That common, even frequency is everywhere in a > household > >> these days. > >> > >> In much of North America, CHU is an excellent > source for > >> testing since it > >> keeps cesium accuracy like WWV but the odd > frequency of CHU > >> is a real > >> benefit since the chance for beating against > extraneous > >> signals is much > >> smaller than at 10 MHz. Testing at a higher > frequency > >> rather than say the > >> MW broadcast band also provides for a reasonably > good > >> account of how the > >> K3EXREF performs. After installation, I > >> would also suggest not trying to > >> test zero beat K3EXREF against commercial MW or SW > BC > >> stations since their > >> carriers are allowed to deviate much more than > the > >> cesium-based time and > >> frequency standards of CHU and WWV. Commercial > AM > >> broadcast station > >> frequencies are typically only accurate to about > +/- 20 Hz > >> although most are > >> better than that. > >> > >> The K3's 49 MHz oscillator is only adjusted at > intervals > >> between 4 and 8 > >> seconds by K3EXREF in order to minimize jitter. > The > >> K3 retains its original > >> phase noise performance since the external > reference is not > >> used internal to > >> the K3's frequency generating scheme. Think of > it > >> this way -- K3EXREF is > >> like lightly touching the 49 MHz oscillator with a > feather > >> every few seconds > >> if necessary to keep it within 1 Hz or so. Also, > the > >> K3 frequency stays > >> accurate even at the moment of powering up the > K3. > >> Kinda' fun to watch the > >> 49 MHz oscillator display change during warm-up as > it's > >> being corrected and > >> compared against the external reference. > >> > >> External references: There are three primary > types, > >> and all can be > >> purchased for less than USD $150 on the used > market. > >> Cesium standards (a > >> fourth type) are also available but are generally > much more > >> expensive, > >> complicated, and won't offer any benefit to K3 > users since > >> K3EXREF limits > >> resolution and accuracy to about 1 Hz. > >> > >> The first type is the GPS Disciplined Oscillator > >> (GPS-DO). This type of > >> standard locks itself onto the visible GPS > satellites > >> orbiting the sky. > >> Requires a GPS antenna and is self-calibrating to > the GPS > >> satellites. The > >> GPS-DO's time and frequency averages from the > visible > >> satellites, each > >> satellite having it's own on-board cesium-based > >> oscillator. Long-term > >> accuracy is usually good to at least 1 x > 10^-11. > >> Extreme accuracy and only > >> a magnitude or two behind cesium. Look for > >> Hewlett-Packard Z3801A, Z3816A, > >> Trimble Thunderbolt, Brandywine, Symmetricon, and > Datum > >> models. Short list, > >> but many others available. > >> > >> Rubidium is the next type. No GPS tracking > >> needed. Accuracy commensurate > >> with GPS-DO. No antenna required. Long-term > >> performance is highly > >> dependent on the quality of the optical beam from > the > >> rubidium pump lamp. > >> Look for EF Efratom, Datum, > >> > >> Third, is a high quality oven-controlled crystal > oscillator > >> (OCXO). > >> Requires periodic calibration. Accuracy good to > at > >> least +/- 0.05 ppm and > >> offer the best phase noise performance among the > three > >> types of oscillators, > >> but as noted earlier, the excellent phase noise > attributes > >> of the OCXO will > >> not be carried over to the K3. > >> > >> A shack reference oscillator is good for use with > other > >> equipment too (e.g., > >> frequency counter). Although a bit lossy, > >> I currectly use a Mini-Circuits > >> passive three-way splitter, but one can purchase > a > >> distribution amp to feed > >> many pieces of equipment from a single > oscillator. > >> Unlike the splitter, a > >> DA offers unity gain and very high port > isolation. > >> > >> Finally, be mindful that most GPS-DO and rubidium > units use > >> internal > >> switch-mode DC-DC converters. Switching noise > was bad > >> enough on two of my > >> units that I decided to gut the converters and > used an > >> outboard > >> triple-output linear supply. The Trimble > Thunderbolts > >> that have been > >> retired from the cellular industry require an > external > >> triple-output supply. > >> If choosing this model, get a linear type and > avoid the > >> headaches. > >> > >> Paul, W9AC > >> > >______________________________________________________________ > >Elecraft mailing list > >Home: http://mailman.qth.net/mailman/listinfo/elecraft > >Help: http://mailman.qth.net/mmfaq.htm > >Post: mailto:Elecraft@mailman.qth.net > > > >This list hosted by: http://www.qsl.net > >Please help support this email list: http://www.qsl.net/donate.html > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
