[Antennas] DC voltage on coax

Thu Nov 4 02:10:53 EST 2004

The MFJ-1786 loop antenna uses the coax to run it's D.C. motor control 
voltage from the control box to the variable capacitor inside the 
antenna itself. There is no separate control cable, the motor voltage 
passes through the coax itself.
Ray Brown wrote:
> ---- Original Message ----- 
> From: "Nelson Wittstock" <k8djc at zoominternet.net>
>>>I am currently enjoying using a pennant receiving antenna for 160 meters. I
>>would like to add another for a different direction but this means having a
>>DPDT relay at the junction of the pointed ends. I need to get voltage to
>>the relay and I would like to do this by routing the voltage through the
>>coax feed. Can someone direct me to a site showing how this can be done? I
>>know I have seen plans for it but cannot find the information now.
>>> Hmmm. Yes, I know it can be done, one application of putting DC on a
> coax line is to run one (or several) signal amplifiers in a hospital's telemetry
> system. We have a grid of 11 "branches" with 6 amplified antennas on
> each branch. A bit of a mess, but that's how you cover a 350-bed
> hospital. :-) Oh and BTW, the antennas are at 608-614 MHz, which is
> why we need amplifiers, a very high loss on small coax.
>> I'll see if I can dig up some schematics on the antenna tomorrow.
>> _Ray_ KBØSTN
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-- 
__________________________________________________________________________ 
Alan Zack
Amateur Radio Station K7ACZ
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