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
