Hi Ian,
Thanks for the info. I will assemble a bias tee and check how it performs
with 127vac.
73,
Felipe
Felipe Ceglia - PY1NB
-------------------------------------------------------------------------------------
PR1T team member /// Rio DX Group member /// Araucaria DX Group member
http://dxwatch.com /// http://reversebeacon.net /// http://riodxgroup.com
On Wed, Jan 15, 2014 at 2:53 PM, Ian White <gm3sek@ifwtech.co.uk> wrote:
> K1TTT 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.
> >
> The story about "molten" CATV cable sounds like someone connected it to
> the 115/230V AC mains.
>
> >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.
> >
>
> Here you go... <http://www.ifwtech.co.uk/g3sek/in-prac/best-of.htm#0904>
> To download the complete magazine article, click "April 2009".
>
> I have used these bias tees for many years to feed AC/DC power for
> remote antenna relays on along both receive and transmit feeders. The
> same design covers Top Band to 6m and comfortably handles 1kW of RF.
>
>
> 73 from Ian GM3SEK
>
>
> >-----Original Message-----
> >From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
> >David Robbins
> >Sent: 15 January 2014 12:36
> >To: felipeceglia2@gmail.com; towertalk@contesting.com
> >Subject: Re: [TowerTalk] AC/DC injection on CATV hardline
> >
> >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@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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