Homebrew Antenna/Rig Switches

Hi All,

I hope you're all keeping well and enjoying your radio pursuits.



I'm a very lucky man (or consider myself so) in that I now have several radios at my disposal for a bit of on-air fun. Some radio were presents, others gifted (including a couple in need of repair) and another was graciously donated with many thanks for their generosity.

They're all very different in the frequency/bands they operate on and even those that operate on the same bands behave very differently in how they function, connectivity, pick out signals, etc. (Not many are lucky enough to compare two or more radios at once but the differences can be very similar or strikingly different!)

The problem I now faced is that I wanted to hook up all these radios at once. (Greedy git! ) I'd become tired of diving into the back of the radios to disconnect the coax only to scrabble around connecting a different radio and rearranging the shack bench. I needed an antenna or rather transceiver switch....

For anyone who's looked at hooking up several radios to one antenna system may have come to realise that it's a bit different from hooking up many antennas to one rig. Simple cheap antenna switches won't cut the mustard with minimal isolation (if any!) if you want to prevent accidentally transmitting from one rig into another damaging it's front end!  

(I'm pretty sure that's what had happened to my old Yaesu FT757gx I'd been given as it was deaf as a post and I had to replace the many diodes in the front end including all the band-pass filter switching diodes.)


Luckily there are many other Hams and radio enthusiasts that can point us in the right direction with helpful insight into what we require. One such example that's very good comes from Alan W2AEW in the form of a Youtube video as follows :-

https://www.youtube.com/watch?v=lMMql1gEORQ

Great explanation there as ever and if you get the chance you ought to check out some of his other videos as he's a very helpful chap.  

Unfortunately my pockets don't extend to such luxuries as 'Alpha Delta' switches which can safely be used in 'reverse' so I did my usual and decided to build one (or two) units myself.


With a few choice pieces ordered on a slow-boat-from-China (bargain prices if your patience holds) I scrabbled together the bits needed including a couple of scrap aluminium extruded casings along with some aluminium sheet offcuts. 'Fancy' switches are not needed if you know what you are doing and some standard heavy duty DPDT (Double Pole Double Throw) switches can be easily pressed into service.

So after a bit of cutting, filing, drilling, etc. I landed up with my first switch unit :-



Not the prettiest looking thing I know but is certainly up to the job at hand. 
(Thanks to my CT friend Alan MW7TTA I was able to check the isolation properties with a NanoVNA he gifted me some time back.)

Here's a couple more shots showing how it's made up :-

Rear view.



Internal view showing the connections.
(Including that big ugly hole that needs covering. )



Plus a close up of the actual switch wiring.



Worked out alright didn't it?

(Some thin aluminium sheet will cover that ugly hole in the casing made by a previous owner and if extended beyond the width allow me to screw it down to my bench/shelf so it doesn't wobble about when toggling those lovely big switches.)

Wiring?

OK then, here's a copy-and-pasted image of the connections from my 'clipboard'. (Literally! )



(Ha! Tickled me anyway.)


I've included the concept of how utilising one switch can switch two radios to one antenna and how the simple addition of another switch allows me to connect three.

Testing with the NanoVNA showed that I had a good 74dB isolation up at VHF frequencies going to some 85-88dB down at HF frequencies so should more than handle my radios operating at my licence limit of 25W and even accidental outputs of 100W. (My IC-706 has a nasty spike of full power on key up much as that whole series does.)

Great stuff, I now have three radios all hooked up to one antenna and can switch at whim. Handy as I have one hooked up for digi-modes, another which is great for voice and a third with a MARS wide band modification.

The secret to this success is firstly knowing what you're doing (don't be hooking up your radios in such a way if you don't!) and grounding unused connections hence the double-pole aspect of the switching.


Flushed with success and having more parts than I initially needed (bulk discounts are handy) I went on to build another unit but this time enabling me to switch between two radios but also selecting between my horizontal and vertical antennas for VHF/UHF work :-

Front view.



Rear view.



A bit of the internal wiring too.




Similar stuff as before but wired differently as shown below :-



Simple really eh?


Now honestly, please do not consider building these if you're unsure of your wiring/soldering capabilities as the consequences would be disastrous if you should get anything wrong. I won't be accepting responsibility for your mistakes.


Any additional helpful tips?

See that 'blue' covering on the machine screw nuts....that's a bit of the wife's enamel nail varnish used as a thread locking compound.

Also those lovely copper wires.....they're covered in varnish (the simple 'wiping' kind) to prevent any corrosion.

All tooling was done by hand and you should allow 'jiggle' room such as drilling 3.5mm holes for the 3mm screw holes on the connectors to allow for slight misalignment. (Was quite pleased the SO239's weren't all on the 'wonk'! )

OK, for the case markings I simply used a Stabilo permanent fine line pen hand drawing as best able. Not the 'purdiest' but does the job.  

So there you go, a solution to an issue I had for my radio fun.




Apologies for my usual 'waffle' and the picture rich posting but I thought I'd once again post up what I've been up to as you never know it might just help someone out. 

It all keeps my brain going, exercises the bear paw hands, makes me don my multitude of different strength reading glasses and great to provide one's own solutions to age old issues. Plus it might add a bit of interesting reading material to the CT pages.


All the very best,
Victor

26CT3228
M7VIC

Interesting once again Victor just wish i had your patience but you do a fantastic job with things like this. 
I did try 2 shop bought Diamond 3 way switches linked back to back at one time.
Had 3 antenna's into 3 radio's.
It's still screwed to the shack wall but as i don't swap around much not used.
It was handy at one time but i would think a lot of loss involved with it setup that way but not sure.

Cheers Alan mate, you know how I love getting up to things such as this.

Thanks to your donation of the NanoVNA (a few years back now mate!) I've used it for all sorts including checking the isolation on these switch units. I did check the losses as best as I could and with numbers around the -0.1dB mark decided that was acceptable enough for the flexibility gained of switching over radios. I still have to check at UHF but the isolation was still way above the 60dB mark which is good enough for me especially as I'd only be hitting the local repeater up at those frequencies.

The handy thing is with multiple radios is that I could be working HF FT8 as well as checking out 2m/70cm at the same time and quickly switch over radios at my whim. (That put a 'shack-in-the-box' idea out of my head. )


Weirdly (and maybe pleasantly) I've seen that my old FT757 seems to pluck signals out that can't be heard over the noise on my other radios but maybe because I restored and realigned her or the analogue nature is more befitting to my deaf old ears(!)

Either way it's all been fun and for me anyway that's what it's all about.

It's all good fun my friend.
I do the ft4/8 plus the 2m/70cm but the 991a has the white stick antenna on it's own no splitter on that one.
Did set up wires-X on it last week or was it the week before i think it was lol but i use a raspbery hotspot to link into that.
Being honest i have never been one to have more than one radio on at a time until just lately repaired so many truckers cb set's years ago when they have sat talking all in the same truck stop.
Just had a visit from an old ham of 50 years he call's weekly and has been trying to get ft4/8 running and today he owned up to his clock being 5 or 6 seconds out i nearly wet myself but he went away happy when i showed him the program to keep the pc clock at the correct time.
All good fun.

Edit
Love it the M7 showing the G0 how lol must remember that next week when he comes round.

We can all help each other out Alan mate irrespective of our licence level.


(I have a constant reminder in my shack that states "It is not the class of licence the Amateur holds but the class of the Amateur that holds the licence." )

Sometimes when my old M0 mate telephones me I say "Hello, Technical Support, how may I help you?"


I've been looking again at DMR and hot-spots more recently.....and might need to pick a few brains to suss that little lot out! Always something to learn with the radio interest and what makes it so awesome.

Hello Victor and Alan,

That is a cracking piece of work and a great write up, too!

That is a really neat and tidy piece of equipment you have constructed. Your skills are top notch as usual.

Have fun with it all and good dx.

73s John.

Cheers John mate, very much appreciated my friend.

Spent the day making up new patch leads to get this little lot all hooked together and working out well so far. Bit disconcerting at first despite having faith in my measurements of transmitting from one radio whilst another is hooked up to the same setup. I needn't have worried though as even on the same frequency I get an S9+ signal at most and all but disappears a few kHz off so all is good.

Looking forward to getting everything arranged and screwed down in the shack so that I can enjoy my version of radio heaven.


All the very best to you,
Victor

Nice job

Cheers Bruce.  

It was fun knocking these up and now they live permanently in my station.

73