I have a mint Realistic "Cb Phone" Trc-456 that puts out a full 4+ watts of power on TX, which is great barefoot, but it does not play well with my amps (negative swing bigtime). I wondered if anyone knows if you can turn down the TX power by adjusting L903 or will this mess with the modulations? Is there a variable deadkey mod for this radio (I believe it is a Cybernet board?). Can't seem to find much info on this model, but I love the car-phone design and would love to have it with a little extra power in my antique farm truck. Anyone have any knowledge they can share on this? Tnx!
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Realistic Trc-456 reducing power output or variable dead key mod?
- Thread starter BahamaDon
- Start date
I guess if I mark L903, and keep count of how many turns, I can always put it back if it doesn't work.
You can do that or just turn it back the other way till you hit your 4 watt deadkey again.
I would set the AMC to 8 watts when you talk into the mic if you set it at a 2 watt DK. Hell even 6 watts with a 1.5 watt DK would still work for even something like a RM Italy 203 foot warmer.
Not sure where an additional external knob for a carrier-power control would go on that one. The Peel'n Stick carrier-control module we sell would work, but teasing out the nitty-grittys to install it have never been done for that model. I'll have a look at CB209 next time I'm at work. Seems that just putting a trimmer pot in place of the full-size control would let you set the carrier to suit an amplifier. Set and forget. There's probably room for the module inside the radio, even if there's no good spot to add an external knob.
With any luck I'll be able to put my hands on Sams CB209 when I go to look for it.
73
With any luck I'll be able to put my hands on Sams CB209 when I go to look for it.
73
Thanks, I had a medical issue in the family so I just had a chance to get back on here. I need to open my radio up I guess and see if there is a decent place to put a module. I would be fine with the mini-pot inside, as it will be set up for just one amp in one vehicle, and left there.
I just love the look of the Trc-456 in an early 80's pickup truck and it is a pretty darn good radio barefoot. Im sort of deciding between this radio or a Lafayette Com Phone 23 with some PLL mods that I also have (or maybe modding the PLL in the 456 too). Whichever one ends up in the truck, it will be permanent, as I use the truck for work on my farm, and actually need a good CB in it.
Can someone tell me if this radio has a similar chassis that might be on CBtricks?
looks like it uses the UPD861 PLL but i need to know which radios share the same PC board.
This radio is a perfect candidate to use the anti spiking diode to reduce deadkey.
do not de-tune L903 to lower power as you are actually causing an impedance mismatch when you do that.
peak it for max modulated wattage.
the useless delta tune switch on the front could be used for three different power levels.
i just need a schematic or info on where to find one and i'll post how to do the mod.
LC
looks like it uses the UPD861 PLL but i need to know which radios share the same PC board.
This radio is a perfect candidate to use the anti spiking diode to reduce deadkey.
do not de-tune L903 to lower power as you are actually causing an impedance mismatch when you do that.
peak it for max modulated wattage.
the useless delta tune switch on the front could be used for three different power levels.
i just need a schematic or info on where to find one and i'll post how to do the mod.
LC
Don't know if it helps any, but the TRC-456 is allegedly in Sams CB-209. Which is, of course, one that I'm missing.
It seems like it might be the same board that's in the TRC-431.
if someone can confirm that for me i can type up how to do the mod.
LC
if someone can confirm that for me i can type up how to do the mod.
LC
BahamaDon,
This mod works on pretty much all old AM only CB radios that use a modulation transformer.
the difference is the part numbers. without CB209 i can't be sure of the exact numbers but i can tell you that your TRC465 is basically the same board as the TRC424 and the TRC431.
the only real difference is the part numbers.
so, what you are looking for is the big black diode that is connected to one end of the modulation transformer in the back of the radio. the other end of this diode will connect to two RF coils, one for the driver collector and one for the final collector.
This diode serves to stop any back EMF from popping the transformer windings when you unkey your mic.
it, by it's nature, lowers the DC voltage to the driver and final by about .6 volts.
If you add more rectifier diodes in series with it (all banded ends facing the same way) each additional diode will lower the voltage by another .6 volts, thereby lowering your deadkey.
the reason this works is that the modulation also comes through on this line and because the diode is already forward biased, the modulation comes through 1:1.
this means that the modulation peak wattage won't be lowered, only the deadkey.
it may take four or more diodes in series to get the deadkey where you want so you'll want to make your assembly as small and compact as possible by soldering the diodes together like this: /\/\/\/\/\
then, if you want to get fancy, you can attach wires at certain points and connect them to that delta tune switch on the front in a way that will "jump out" or short across a certain number of the diodes.
this way, you could have three different deadkey levels.
you'll need to work this all out in order to jump the right wires that used to go to the switch and all that but it could be pretty cool.
in the TRC431 this diode is labeled D508. in the TRC424 its D507. not sure what it is in yours but probably close to that number.
the diodes you want to use are 1N4003 diodes.
best of luck!
LC
This mod works on pretty much all old AM only CB radios that use a modulation transformer.
the difference is the part numbers. without CB209 i can't be sure of the exact numbers but i can tell you that your TRC465 is basically the same board as the TRC424 and the TRC431.
the only real difference is the part numbers.
so, what you are looking for is the big black diode that is connected to one end of the modulation transformer in the back of the radio. the other end of this diode will connect to two RF coils, one for the driver collector and one for the final collector.
This diode serves to stop any back EMF from popping the transformer windings when you unkey your mic.
it, by it's nature, lowers the DC voltage to the driver and final by about .6 volts.
If you add more rectifier diodes in series with it (all banded ends facing the same way) each additional diode will lower the voltage by another .6 volts, thereby lowering your deadkey.
the reason this works is that the modulation also comes through on this line and because the diode is already forward biased, the modulation comes through 1:1.
this means that the modulation peak wattage won't be lowered, only the deadkey.
it may take four or more diodes in series to get the deadkey where you want so you'll want to make your assembly as small and compact as possible by soldering the diodes together like this: /\/\/\/\/\
then, if you want to get fancy, you can attach wires at certain points and connect them to that delta tune switch on the front in a way that will "jump out" or short across a certain number of the diodes.
this way, you could have three different deadkey levels.
you'll need to work this all out in order to jump the right wires that used to go to the switch and all that but it could be pretty cool.
in the TRC431 this diode is labeled D508. in the TRC424 its D507. not sure what it is in yours but probably close to that number.
the diodes you want to use are 1N4003 diodes.
best of luck!
LC
