.
/
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?
Back to top of page
.
/
.
CB Radio Repairers in the UK
CB Radio History from its early days