For remote control of a Beverage antenna selector, N4ZR has had good
success with sending the 300MHz control signals out along the same coax
that carries the incoming 160/80m signals. That same coax also carries
DC power to the preamps. I believe that Pete documented this in NCJ.
The range of an ordinary over-the air control link is limited and patchy
because the radiated signal spreads out in all directions and is almost
entirely wasted - only a tiny fraction of the power radiated from the
transmitter will fall upon the receiving antenna. The control receiver
has to be quite sensitive to compensate for this huge path loss... so
now the good news: This also means that the range of a direct
point-to-point control link over coax will be practically unlimited! You
will always hit some other practical limit first, like the size of the
property or the losses of that same coax at the primary HF signal
frequency.
For his receive-only application, Pete was able to use simple proximity
to couple the 300MHz control signals into the coax and out the other
end. A more formally-designed type of signal coupler was not necessary
because the control link has lots of decibels in hand. With
purpose-designed signal couplers, it would be equally possible to send
low-level VHF/UHF control signals along the same coax as 1500W of HF
power.
73 from Ian GM3SEK
>-----Original Message-----
>From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
>Jim Lux
>Sent: 18 June 2013 05:38
>To: towertalk@contesting.com
>Subject: Re: [TowerTalk] Coax and control lines in same PVC (Steve
Jones)-
>Option
>
>On 6/17/13 11:51 AM, Joe Subich, W4TV wrote:
>>
>> You still need to provide +12V to switch the relays plus power for
the
>> WiFi receivers *and* protect the sensitive receivers located at the
>> base bottom of a huge lightning rod from damage from both water
(rain)
>> and lightning.
>>
>
>yeah, but those "sensitive receivers" these days are <$20 and it would
be
>fairly easy to build a "lightning proof" box that passes 2.4GHz (slots)
>
>Actually, you might want to look into something like aircable, which is
a
>long range bluetooth type interface.
>
>
>
>> Copper control cables with proper lightning protection and relay
output
>> controllers are far more reliable and damage resistant than small
signal
>> (WiFi boxes) devices.
>
>For the cost of hundreds of feet of multiconductor wire and those
>protection devices, you can probably buy a lot of WiFi interfaces.
>
>I'm not sure what the most cost effective architecture would be.
>
>And if you are running copper the whole way, then Ethernet (using
fiber)
>might be a good approach.
>
>You still need power, as you point out, but I would send 110V out, and
>put a power supply at the base of the tower.
>
>
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