[time-nuts] GPS antenna distribution from a DTV multi switch
stanley_reynolds at yahoo.com
Sat May 8 14:29:42 UTC 2010
Have been using a sat passive splitter and most of my cables are using F connectors so I'm thinking of modifying a DTV multi switch to provide 5 volts instead of 13 volts on the LNB/antenna port. Antenna is a Trimble bullet II 5 volt antenna. The switch is active and I would ignore the 22Khz and 18V inputs, just need the extra outputs and amplification. I've opened it up and it ( a eagle aspen DTV4X8 ) has two lm317's maybe for 18 and 13 volts as well as a ua78m06 for the amps and volt/22Khz switches.
1) add a 78m05 for the GPS antenna between the 13 volt supply and the RF choke (my first choice)
2) adjust the 13 volt lm317 regulator to 5 volts by adding a resistor in parallel with the existing resistor
3) cut the 13 volt feed and add a diode .7 volt drop from the 6 volt supply
Please let me know what you think. I have read the 50 ohm vs 75 ohm cable discussions and due to cost and ease of using f-connectors will live with the mismatches for now.
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