Seeking Realistic trc452 advanced audio tweaks

[Handy Andy]

Sigh...

 

[Uncle Ronnie 336]

I hear that. And I thank you very much for helping me get this thing going. So before I got to bed last night I did manage to make it do something along the lines of passing audio. I am unsure if I cooked the 1969 in there or not

 

[Uncle Ronnie 336]

I have ordered some driver transistors so now we wait.

 

[Handy Andy]

Well, as least you're still working on it.

Be careful with it, some of the parts are unobtainium due to age.

 

[Uncle Ronnie 336]

I ordered a 10 pack of 2314s. What's a good starting point for the bias resistor on that? The stock one is 220 ohm

 

[Handy Andy]

100 ohm, usually in the 2314 types From Base to Ground..

TRC-452...does it this way...Note R261 - your 220 ohm.


A Realistic that uses 1957, But Coil GROUNDS DC to Base lead, a coil coupled design. R911 is your 100 ohm/220 ohm - but now a 68 ohm at R911 - but R912 is a BUFFER resistor (added to protect the 2314 or whatever part you use in there) in this design.



1957's are what's used in most Cobra 25 and 29's these days...
Note, they use a COIL to couple, not a direct connection via capacitive coupled

Other Realistics that use the 2314 - do it a little differently...
This one is the closest to your design I can locate easily in the R/Shack line..



But resistor R307 - 100 ohm...This resistor is the one that goes to Base. L303 is the peaking coil from the preceding stage, the predriver - like in yours. But the cap values (C306 and C307) are tweaked to offset the drive level (output) from the Predriver. The caps act as a power divider to split RF power arriving into this stage, from being too great, or strong signal overload - so they "split it" by shunting some signal with a cap to pull power away and in this fashion, takes many of the spurious harmonics along with it, into ground. A way to clean up a signal when you don't know how much "dirt" in there mixed in with it from the local oscillator and mixer sections sending power to it.

 

[Uncle Ronnie 336]

So does that mean I should leave the cap parallel to the bias resistor alone or should I drop a 330p in there?

 

[Handy Andy]

It has one already, but if it (new Driver) goes up in temperature - as in; gets very hot rather quickly - then you'll need to UP the value of that cap to 330pF - else just get it to fire and check temp first.

That cap is a divider to keep drive, and harmonics - from getting too far into the TX strip - causing other problems.

 

[Uncle Ronnie 336]

I think after I am done with this I am going to buy one off of eBay and try to do a mosfet output on it.

 

[Uncle Ronnie 336]

I wish CBtricks was still updating. I think out the other end of this project there should be a write up for others to reference on this radio. Like, do these steps, make it scream, leave c350 alone.