T23, toll free's advice is correct as far as how to lower the deadkey on your 434 goes, so ill elaborate a bit on it to help familiarize you with the procedure.
as for your question about SSB, well, since there is no deadkey on SSB, there is no need to lower it. unless your radio puts out 35-40 watts PEP, you wont have any problem running an amp on SSB. even then, many amps will handle that kind of PEP.
ok, what toll free was saying applies to pretty much any AM only radio that uses a modulation transformer. pretty much all radios that are AM only are like this except for the galaxy chassis, the exports and maybe a few others, but those types of radios have internal adjustments to lower deadkey.
to determine if your radio uses a modulation transformer, look at the schematic for your radio and find the audio chip. right next to the audio chip you will see the symbol for a transformer that has one end connected to the audio chip and the other end runs to the collectors of the final and driver transistors.
we will use the 29LTD as an example because i cant find a schematic for your radio online, and the 29LTD is very popular.
your radio will be the same in this respect, except the part numbers and physical locations will be different.
here is a link to the 29LTD so you can follow along:
http://www.cbtricks.com/radios/cobra/29ltd_29ltd_st_29wx_st/graphics/cobra_29_ltd_classic_sch.pdf
first find IC4, which is the audio chip. look at the pointy end and you will see pin 9 is connected to the center tap of one side of a transformer, in this case labeled T1. this is your modulation transformer. (your 434 has one of these)
now look at the top of this side of the transformer. you will see that it is connected to a line that connects to pin 1 of the audio chip.
this line is connected to the 13.8 volts coming into the radio.
you can now see that the 13.8 volts flows through this side of the transformer, the modulation is added to it via the center tap, and all of this is sent to the collectors of the final and driver transistors (TR14 and TR15 in the 29LTD) through D8.
See D8? its just below T1. this is the diode that toll free was referring to, and this is the diode that you will find in your TRC 434.
it is always a black rectifier diode that looks just like the reverse polarity diode. they are also usually close to eachother so dont get them mixed up.
ok, all that explaining was necessary so you can apply what you just learned to pretty much any old AM radio to lower the deadkey while keeping the PEP swing in a peaked condition.
now we can move on to your radio, and even though we dont have a schematic, we can apply what we learned about the 29LTD to your TRC434.
first lets find the modulation transformer.
look in the rear of your radio, and you will see one, two, or maybe even three transformers. (usually only two)
one of these is for power filtering and is in series with the positive lead coming into the radio. this is NOT the transformer you want.
look for a transformer that has one lead connected to a multi-pin IC chip that will be mounted to some sort of heatsink or the chassis itself. (this will be your audio chip)
this same transformer will have a different lead connected to the unbanded end a rectifier diode which will be mounted near the transformer.
the banded end of this diode will connect to a PC board trace that runs to both the driver and final transistors, usually through a coil or something.
this diode is whats known as an "anti-spiking diode", and its job is to prevent any voltage/current from getting back into the transformer when you key and unkey your mic.
think of it like a one way valve.
this "valve" does provide just a bit of resistance, and lowers the voltage going to the driver and final transistors by .7 volts.
if you were to unsolder and lift one end of this diode and add another rectifier diode in series with it (making sure all the banded ends are going the same way). it would lower the voltage to the driver and final by 1.4 volts.
three diodes in series would lower the voltage by 2.1 volts and so on...
this voltage is what determines your deadkey wattage.
lower the voltage, and you lower the deadkey.
so, add one diode in series and check the deadkey. keep adding more diodes in series until you get the deadkey that you want.
the cool thing about this mod is that it only lowers the voltage for the deadkey, when the modulation comes through, it still swings as high as it did with the original deadkey wattage.
this is because the diodes are already conducting and the modulation gets coupled through 1:1.
you should enclose your new diode "string" in heat shrink tubing.
the diodes you want for this are 1N4003's or NTE116's.
you should never lower the deadkey with the tuning coils such as L11 in your 434. these are impedance matching devices and should always be tuned for peak modulated wattage.
this means that BEFORE you start your diode mod, you should adjust L11 for max wattage while saying "ahhhh" into the mic.
L12 is probably an untunable trap coil and should not be messed with. (dont spread it!)
ok, this should give you a 2 watt deadkey and the full swing the radio is capable of, as well as allow you to do the same thing to many radios.
good luck,
LC
