I'd think the capacitance of the coax would present problems. Before I got the cannonical antenna for my Austron LORAN Rx, I used a roughly 30" square of 3/4" Cu tubing threaded with a bunch of #18 insulated hookup wire. The slick glop electricians use helped a lot. What a mess though.
-John =============== > I have been very superficially following this topic and looked at some > links about 60 KHz Loop antennas, including one on Tom's site (I think?) > describing building one out of 100 feet of RG58 coax. > > Could CAT 5 cable be used? It is 4 twisted pairs and you can get it > shielded. Any issue with 'twisted pairs'? > > Joe > > -----Original Message----- > From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On > Behalf Of J. Forster > Sent: Sunday, October 03, 2010 1:48 PM > To: b Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] 60kHz Loop antenna > > > I observed a diurnal phase shift with my 117A system. I never investigated > whether this was due to loop phase shifts with temperature or propagation, > but it was likely a combination. > > These phase shifts matter less if you are doing long term (multi-day) > measurements, but, to be valid, your system has to maintain phase lock for > the entire time. In my experience, that rarely happens in my location. > Remember a 1 cycle hop is about 16-17 usecond. > > Phase shilt with temperature becomes a real worry if you are trying to > adjust a local standard in a few hours or a day. > > FWIW, > > -John > > ================ > > >> John,-"My concern with tuning the loop is that as the tuned circuit >> drifts with temperature, or other things, an extraneous phase shift >> will be intoduced to the received signal. Remember, the phase of a >> complex pole pair tuned circuit goes from +90 to -90 degrees as you >> sweepo through resonance. The higher the Q, the steeper this effect >> would be." >> +++++++++++++++++ >> Don Lancaster addresses this concern in his article where he states: >> ââ¬ÅTune this coil to 60 kHz with high quality polystyrene capacitors >> or the more expensive >> silver micas. Any other capacitor type is unsuitable. The coil Q should >> be >> around >> 25 to 40. More will cause temperature and tuning problems, less will let >> in too >> much noise.ââ¬Â >> >> To tell the truth, I really haven't given this much thought for the >> 30+ years my loop has been working. >> >> à à à à à à à à -Arthur >> >> >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.