[ntp:questions] Roof antenna, which one, would you bother?

Brian Inglis Brian.Inglis at SystematicSw.ab.ca
Sun Jan 5 21:20:11 UTC 2014


On 2014-01-04 05:01, David Taylor wrote:
> On 03/01/2014 19:58, Brian Inglis wrote:
> []
>> Instructions are on David Taylor's site at
>> http://www.satsignal.eu/ntp/FreeBSD-GPS-PPS.htm#usb
>> I simplified the wiring shown in the above link by connecting
>> all +5V power leads to pin 6 DSR.
> []
>
> That's a good simplification, Brian.
>  But as RS-232 can be up to 25V (according to Wikipedia) how do
> you guarantee than the GPS 18x LVC won't be damaged, and that
> enough drive current is available from DSR?
>
> I'd like to add your suggestion to my Web page, but I don't want
> people damaging their GPS receivers by injudiciously following
> your advice.

I was not clear - I connect USB power to DE9 pins 5/GND and 6/DSR(+5V)
and also connect the GPS GND and power leads to those pins.

As the GPS is connected as a DCE (comms/modem) where pin 6 is an output,
and the PC as a DTE (terminal/device) where pin 6 is an input, no RS-232
interface should have a problem with +5V input on DSR.

I skipped the PPS LED as I could not find any low current LEDs locally and
the 18x LVC 5V at 90ma power requirement is close to the USB 5V at 100ma limit.
Instead I used your http://www.satsignal.eu/software/net.htm#SerialPortLEDs
program (thanks for that) to check PPS on DCD, and Garmin snsrxcfg
http://www8.garmin.com/support/download_details.jsp?id=4053 to set up and
check the configuration and sentences generated.

-- 
Take care. Thanks, Brian Inglis


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