I did think about extending the RS-232 cable, but with it would also have to go a USB cable extension to power the board. Although now that you mention it, and I sit here and ponder that idea, maybe that is the better solution. Although instead of running a RS-232 cable plus USB cable "as-is", just get a 50ft RS-232 cable, splice it, and utilize 2 wires for the USB power. I suppose that prompts the question, which RS-232 pins are unused?
Correct me if I'm mistaken, but are pins 4 & 6 thru 9 unused? On Mon, Oct 22, 2012 at 11:15 PM, Hal Murray <[email protected]>wrote: > > [email protected] said: > > I have a Sure Electronics GPS board and I want to extend the antenna > cable > > several feet. Is anybody able to confirm the RG cable type and coax > > connector of the antenna? My assumption is it's a RG-58 cable with a SMA > > connector. > > It's probably easier to extend the RS-232 cable. :) > > ---------- > > There are 2 issues with coax. > > One is loss due to skin effect and dielectric absorbtion, measured in > dB/meter. It's frequency dependent. GPS L1 is 1.4 GHz. Most coax is > generally not great at that frequency. > > The other is loss due to impedance mismatch. Most lab setups use 50 ohm > coax. Cable TV uses 75 ohms. > > In general, bigger coax is lower loss, and for the same outside diameter, > 75 > ohm coax is lower loss than 50 ohms. > > Most decent coax uses foam-polyethylene for the dielectric. The air in the > coax is close to zero dielectric loss. > > Most GPS antennas and receivers are setup for 50 ohms. Trimble points out > that the loss due to impedance mismatch is low compared to not-many feet of > readily available coax, so RG-6 works better than you might expect. They > ship RG-6 in their evaluation kit. > > ----------- > > The thin cable on the Sure antenna is probably RG-174. > > RG-174 is 50 ohms. It's 1/10 inch dia, high loss. > (but flexible and inexpensive) > RG-58 is 50 ohms. It's about 1/4 inch in diameter. > This is standard lab coax. > RG-59 is 75 ohms with roughly the same diameter as RG-58. > RG-6 is 75 ohms. It's slightly bigger and significantly lower loss. > It's widely available as low-loss cable TV coax. > LMR-400 is about 1/2 inch in diameter. It's 50 ohms, low loss, and > expensive. > > Lots of good info here: > http://en.wikipedia.org/wiki/Coaxial_cable > > > > -- > These are my opinions. I hate spam. > > > > _______________________________________________ > pool mailing list > [email protected] > http://lists.ntp.org/listinfo/pool >
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