My original Remote Antenna
switch was made specifically to select the various driven
elements on my Quad. This works extremely well, and was
simple to build. I then realised that remote switching for
all of my antennae would have a number of advantages.
A large reduction in the number coax
"runs" from the shack to the various
antenna locations, thereby making a considerable
saving in cost, and complexity, of switching antennae
from the shack.
A few runs of expensive, high quality
"hard line" coax to the main antenna
switching points outside the shack, is CHEAPER than
running seperate runs of RG213 or similar, to each
individual antenna all the way from the shack.
If an electrical storm heads in your
direction, it is comparatively easy to unplug two or
three coax lines and control cables and throw them on
the lawn before you hide under your bed..!!! Also,
all unused antennae have their coax feeds shorted to
ground at the remote switch boxes.
It is easier to experiment with new,
or temporary antennae, as you can hook into a spare
point at a remote switch, rather than run a temporary
coax all the way back to the shack...And of course,
"temporary" set-ups have a nasty habit of
becoming permanent "eyesores"...
There is an overall reduction in
general"clutter" in the shack, making
operating easier, and perhaps even earning the
coveted "XYL seal of approval"...
There are two disadvantages to "Remote
The cost of the
switches....Negligable, if you build them
yourself.... We're Experimenters....Right???
If you lose your electrical supply to
your home, in a storm, or for other reasons, you have
no control of your antenna selection.
As regards the second scenario, I have
always made a point of having an emergency supply available.
I have a standby 3KVA generator, and also a bank of four
large 12V automobile batteries wired in parallel. All my
remote switches use 24V DC relays, so I series a small 12V
battery with the other four to give me my emergency 24v
supply. I have no preference for 24V relays over
12V relays... I use 24V relays, purely because I have a good
supply of high quality relays which just happen to be 24V...
If you have a small antenna setup, with
perhaps a tribander, and a Zepp, or trapped vertical for the
lower bands, then remote switching is not really any
advantage. If on the other hand, you're one of the lucky
ones, and have lots of space for lots of antennae, then you
should probably take a look to see if it can be of advantage
in your situation.
In my own case, (I'm one of the lucky ones)
I live in the country, on the coast, and my site is
approximately 1/2 an acre. I have permission from my farmer
neighbours to erect whatever antennae I like, in the
surrounding fields, so long as I do NOT interfere with the
agricultural activities in any way whatsoever. I have erected
four large (45-60ft) timber poles at various locations on the
boundaries of surrounding fields. I have a 55ft tower at the
back of the house, and a couple of verticals in another
corner of the garden. I have a 4insOD plastic conduit running
underground from the shack to the tower...120ft. Another
conduit to the Verticals about 80ft. But the run to the 60ft
pole in the field is 900ft...Yes ...nine hundred feet..
I run three coax lines to these locations,
and have one or more remote switches at these three antenna
sites. For instance, at the tower, one coax line feeds the
eight bands on the Quad (40M thru' 6M) and a sloper..Nine
antennae...One coax...one control line.
The switch consists of two units, the
control switch in the shack, and the relay box at the remote
end. The Control Box consists of a small Power Supply
providing 12V or 24V DC to suit whatever relays you are
using. The " + " of the DC supply is connected to the input
of a rotary switch, and the output tags of your switch are
wired to a terminal strip mounted on the back of the box. A
multi-core cable is then run from the terminal strip to the
Remote Relay Box at the antenna site.
( Diagram of
Remote Relay Box.. All unused antenna outputs are grounded)
Most of the surplus relays that I come
across are encased in a clear plastic cover, and have "
OCTAL" bases. Others have flat metal
"pins".Anything that can handle about 240V AC, at
about 10Amps, should be adequate for powers of up to 1.5kW of
RF. ( switching 50 Ohm coax).
You can use these "as is",
soldering the wiring direct to the pins on the bases of the
relays. I prefer to modify my relays, because the long
connecting wires from the base to the switching contacts, are
usually pressing against the relay bobbins. This must induce
RF into the bobbins, and probably introduce a bit of
distruption to our 50 Ohm line. I remove the bases and
plastic covers. I also remove the "flying leads",
and solder a jumper between the two relay switching
"leafs". This shortens the RF path through the
relay,and reduces any extraneous coupling. Hopefully the
drawing below will be adequate explanation of the
( Pic of remote
relay switch box, with modified relays)
MK2 Switch Box
I got some really nice new modern PCB mounting relays. They
are quite small and tidy, but the bobbins are well away from
the contacts. The Contacts are silverplated, and are rated to
handle about 2kW at 240v AC. The use of a PCB, really tidies
up the wiring., and minimises anomolies in the RF path... See
pics below... The local contest station EI7M, recently used
this switch in "battle conditions", and hopelessly
failed to do any damage to it....C'mon guys... Your not
(FINDERtype 40.31 S . PCB mounting 24V relay. They measure
1ins high by 1ins long by 1/2ins wide..approx )
( Pic of relay
box using PCB mounted relays, and PCB board chassis)