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Re: Preamp bypass circuit



Hello Howard,

I have no problem with injecting DC onto the coax to power
stuff up on the tower and as long as you can guarantee you will always
stay within the current limits of the method you use to get the DC
onto the coax.

Right now I am using a SUHNER DC injector to put DC onto my microwave
IF line in the shack. A second DC extractor (injector in reverse) is
used on the tower . DC toggles a SPDT coaxial relay to switch the 2M
IF line from the 10 GHz transverter to the 2304 MHz transverter. The
relay has reasonable isolation at 2M.

I first tried DC from the shack up the tower to power up microwave
transverters.
 I did not use further regulators on the tower, so I had regulation
problems.
After awhile I needed +13 then +15 then +28 VDC so instead of running
separate DC lines I added 2 runs of BELDEN 9913 from the shack cellar
up the tower to a tower top enclosure where I put the power supplies.
I now feed 120VAC up the 2 coaxes, one center conductor for neutral
the second for AC line, both being well shielded from leaking any RFI
EMI into my antennas. Lightning surge suppressors are used on the AC
lines as well as a ground fault current interrupter (GFCI). Also the
AC lines can be easily physically removed or isolated from the house
power wiring.

So far I have not experienced any corrosion issues even though I am
about 1.5 miles from salt water.

Stan, WA1ECF




Howard Long wrote:
> 
> Hello Stan
> 
> Stan said...
> > Please consider avoiding taking DC power from any radio connector.
> 
> What are your concerns taking DC down the coax?
> 
> There's only two reasons I could think of _not_ to do it:
> 
> o If left on a significant amount of time, the DC could cause
> electro-chemical corrosion over time;
> 
> o Yet another in-line device to add to the losses.
> 
> FWIW I run my 30V unregulated up the mast and have done for a year without
> any problems, and upto 2 amps, with two preamps and 10 coax relays.
> 
> Interested to know your thoughts.
> 
> 73 Howard G6LVB
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