'Remote Antenna Switch.'


I 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.

As 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....


     


I 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 sided PCB.
The relays are on one side and very nearly on the exact opposite of the board are the connections to the coaxial sockets.

On 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.

When 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 safety.


No 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 for.

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 PCBs.

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.

And thats about it. :-)


PCB ART.
antsw01.brd
antsw02.brd

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