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Bias-T's and preamps.




What are people using to power preamps and RX converters designed to pull
power off the coax?  This is for a Mode S rx.

I've come across plans for building a bias-t for rigs that don't have the
capability to supply 12VDC onto the feedline.  DEM, ARR, and others sell
them built and tested for low insertion loss but it seems pretty simple.

1) How critical is the construction?  A cap, encapsulated inductor, and
connectors doesn't appear to be that complicated.

2) Do preamps and converters pass the DC up the feedline to "upstream"
components?  e.g.:

                                                    "T"
Antenna--- 2.4 GHz ---- 2.4 -> 2M ---- 2M - 28MHz ------- rig
           preamp       converter      converter     |
           (if needed)  (Drake or      (maybe)      12V DC
                         similar)

Or should I assume that I need to put the bias T before the component(s)
needed power on the feedline?  Or simply make sure everything uses
external power and run a 12V DC line?

Thanks & 73

Steve KA1LM

-------------------------------------------------------------------------
Stephan A. Greene                            sgreene@valinux.com
Senior Systems Specialist, VA Linux Systems  
Amateur  KA1LM@amsat.org  Grid FM18hx        38 59'83.33"N 77 23'6.15"W
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