[time-nuts] RG 6 U couplings

Bruce Griffiths bruce.griffiths at xtra.co.nz
Mon Dec 7 14:23:36 EST 2015


On Sunday, December 06, 2015 10:02:43 AM Mark Spencer wrote:
> I've seen data re delay vs temperature for high end 50 ohm cables.  I've
> never seen it for 75 ohm CATV style cable.
> 
> Back when I was into time nuts pursuits this was one of the main 
reasons I
> was contemplating switching my GPS antenna feed line to hardline.   I 
never
> made the change but still have the hardline.
> 
> To this day I still use Teflon RG58 style cable (purchased surplus from
> Boeing decades ago) for my GPS antenna fee line to the splitter.   I 
doubt
> I will ever change it out.
> 
> Sent from my iPhone
> 
> > On Dec 6, 2015, at 4:21 AM, Attila Kinali <attila at kinali.ch> wrote:
> > 
> > On Sat, 5 Dec 2015 17:06:03 -0800
> > 
> > Mark Spencer <mark at alignedsolutions.com> wrote:
> >> Over the years I've used a number of CATV style 75 ohm patch cords
> >> with F connectors, F female to female couplers and F to other 
connector
> >> adaptors to distribute gps signals from my GPS splitter to various
> >> receivers.   I've never been able to notice any difference in reported
> >> signal strength vs using "brand name" 50 ohm coax with N 
connectors.
> > 
> > Well, putting the numbers into a calculator gives:
> > VSWR: 1.5
> > Load Return loss: -14dB
> > Load Mismatch Attenuation: -0.2dB
> > 
> > I'd say that for a receiver, this is quite negligible. Heck, even 1dB
> > loss wouldn't hurt too much. I would suggest, that for all practical
> > purposes, the use of (good) satellite coax cable would be more than
> > good enough for most of us. The only thing i'm not sure about is how
> > the delay through the cable behaves over time (aging, temperature,
> > humidity). If anyone has some data on that, for different types of
> > cables, I
> > would appreciate getting a copy :-)
> > 
> >            Attila Kinali
> 
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Teflon has a phase transition around 20C or so.
Consequently its phase stability isnt stellar near the transition.
Polyethylene insulated cables are superior in this regard.

Bruce



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