[TowerTalk] AC/DC injection on CATV hardline

[PY1NB - Felipe Ceglia]

Hi Dave,

I will assemble a DC bias tee and check how it performs at 127vac

73 & thanks,

Felipe

Felipe Ceglia - PY1NB
-------------------------------------------------------------------------------------
PR1T team member /// Rio DX Group member /// Araucaria DX Group member
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On Wed, Jan 15, 2014 at 10:36 AM, David Robbins <k1ttt at verizon.net> wrote:

> 50/60hz or dc shouldn't matter.  the only way to get molten cables is by
> too much current, you can do that with either ac or dc, but you need some
> kind of high current source to do it.
>
> There are commercial injectors available, but the old heathkit remote
> switch box used nothing more than a 100mh coil to connect the ac or half
> wave dc to the coax and a .1uf cap to block it from the tx and antenna.
>  you do have to be sure that the capacitor will handle the max voltage AND
> current at the highest frequency, so don't just pick any old audio cap out
> of the junk box, get a good ceramic or tx rated cap.
>
>
> Jan 14, 2014 07:28:16 PM, felipeceglia2 at gmail.com wrote:
>
> Hello folks,
>
> I need to inject AC or DC into a run of CATV hardline (.860)
>
> I've been told by a CATV technician that it isnt a good idea to inject DC
> into it, he couldn't explain why. He mentioned seeing molten cables when
> someone tried to do it.
>
> I got a pair of AC injection boxes, but when measured on the VNA each of
> them presents more than 35dB insertion loss on 1.5MHz...
>
> Do you guys have any expertise on this issue? If AC is really needed, any
> particular diagram? 60hz seems to be fairly close to 1.5MHz to isolate it
> using a single capacitor as done with DC. Maybe a highpass filter should
> help?
>
> 73,
>
> Felipe Ceglia - PY1NB
>
> -------------------------------------------------------------------------------------
> PR1T team member /// Rio DX Group member /// Araucaria DX Group member
> http://dxwatch.com /// http://reversebeacon.net /// http://riodxgroup.com
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