Cybernet 134 Chassis CB Radio's can have their squelch functions altered for the better quite easily. This page highlights three different types of adaption. I will go into detail of all three to give you an insight as to whether this adaption is for you.
Adaption 1 is the first one I became familiar with. The basic adaption some people either love it or hate it. I love it but I go a little further than the basic adaption and make it switchable so you can either have it running or have it as it comes box standard. What this adaption effect does is it seems to turn the background volume down depending on how high you have the squelch control but local stuff comes over the same. It reminds me of a late evening on AM back in the early 80's... you can hear the background stuff which is quiet but the local stuff comes over as normal...with hardly any annoying FM hiss. Sometimes you want a normal squelch though so you can turn this one back to box standard at the flick of a switch.
The first thing to do is to locate resistor R60 which is located behind the signal meter. Where I have circled the resistor you need to un-solder this one end and lift it up out of the board. The now empty hole on the PCB needs a new piece of wire soldering into it, I'm going to refer to this wire as black but obviously you can use whatever colour you like. The other end needs to go to the middle connector of a new switch (The common) which can be an existing switch after having the original wires removed from it or a new one which could be fitted to the back panel of the radio or taped up and left inside the rig. The latter you would have to remove the case to get to it of course so it's probably best for a switch on the back.
Next solder a blue wire to one end of the new switch and the other end needs to go to the un-marked post toward the front of the PCB which already has a blue wire (or two) going to it (see pic).
Finally a wire from the remaining new switch terminal to the raised resistor (which you originally lifted one end out of the board) and if you have any suitable heat shrink cover the resistor and new floating joint to prevent any accidental shorting.... Job done.
This one is really simple. All you need to do is solder in a 10uf 16v electrolytic capacitor across the collector and emitter of Q14. See the pictures of how to fit it. As this capacitor is polarised you need to make sure you fit it the right way around.
What does this adaption do? Well, it isn't going to amaze you or put pounds of value on your radio but it does cut out the popping noise as the squelch cuts in and out. Give it a go and see what you think.
Click on the images for a larger view...
This adaption was tried out on my Rotel RVC-220 and it works just fine. Apparently this also works on the Ham International Puma but put the 16v 10uf cap across the emitter & collector of Q12.
The third one I have never tried so have no idea how good it is but have put the information on here should you wish to try it.
The idea comes from an old diagram drawn by Tony Madden and has been around that I know of since the early 90's.
1/ Add 3K3 in series with the squelch pot 2/ Add NPN Transistor as shown in the diagram 3/ Change C109 for a 1uf for a faster squelch operation
Job done. If you try this adaption please email me and let me know what you think of it?