have in my shack a number of radios on my bench top at
any one time. It
is very convenient to have them all at hands reach , but
it is such a pain to swap cables from one to another
before I can operate them.
The PTT lines are all connected through the audio
control center that I made , but the antennas coaxial
cable still required sliding the rigs forward and
physically moving the cable from one to another ....
what a pain.
For years now I have been doing it this way , and
while I have always had the plan to have a remote
antenna change over switch for 4 rigs , I never got around to
making it .......that is until now.
you do , I scoured the internet for various pages on
the subject for some inspiration , and had found some
interesting constructions , but they all had flaws. Most Hams build them with ease of construction as of
primary importance , and in doing so they often have
long PCB tracks or wires from the coaxial chassis
sockets to their relays.
One example of poor construction that I found online is shown below....
just can't help but think that is a poor way of doing things.
One particular attribute that I realy wanted was having the shortest
path possible in and out of the changeover section. So
I came up with something which honestly I haven't seen
done by anyone else ,,, and no wonder , it is a sure pig
of a thing to build it the way that I did.
Simply explained , the relay board I made with a double
The relays are on one side and very nearly on the exact
opposite of the board are the connections to the coaxial
the relay side of the board I have included a 1N4148
diode and a 0.1uF capacitor across each of the Omron G2R SPDT 12V relays coils.
The relays are energized with power
via a remote rotary switch , nothing too technical at all. I
take my 12V supply from my Yaesu power supply.
The relays are wired up so that the relays
that are not energized have their switching
contact to the rig grounded.
In my application that shorts the coaxial line
leading to the radios in order to reduce RF
pickup when I operate one of my transceivers.
I shut down my radio desk I turn off all the power and
so the switch box will de-energize thereby shorting all
antenna inputs for a little extra static protection
doubt this design could be used with some sort of
wireless switching , and if you did that , you could
have the relay box to switch multiple antennas , instead
of the multiple receiver arrangement that I am using it
Anyway , on to the pic's......
my digital camera has problems and the occasional pic it
makes is unusually fuzzy GRRR....
Notice how the relays are not in line with each other
, they are all staggered.
Doing it this way gave the shortest conductor path on
The round circles have soldered through them wires to
join the upper and lower sides of the board together
in that spot.
That is required as the pins for the coax chassis
sockets would otherwise have no connection to the
lower tracks going to the relays.
At first I used countersunk screws to hold down the
sockets , but found the protruding thread on the top
side prevented some types of cable plugs from
screwing all the way down , these screws have since
been replaced with stainless steel rivets that are
much lower in profile.
The board is supported by the coaxial sockets.
It should be obvious that quite precise drilling is
required on the case and the board so they line up.
Even though , I did all my drilling with a hand held PCB drill and everything worked out fine.
Here are a couple
of view that shows just how tight it is between
the PCB and the alluminium cases lid. It is my guess
that this should be fine for power levels under
500W , but over that arcing may be found.
A braid connects the PCB to ground.
This is purely for the ability to short the RXs to ground when not in use.
If you do not need this feature , then you can ommit this braid.
So far with
this design there hasn't been any problems
with odd relay operation with TX-RF going
through the switch box. In high power
applications though small chokes and beads
may be required to make the switch box
completely RF tight.