This is rework - so you know...
Don't worry, I'm only gently yelling at myself...
Well, not completely rework...(maybe)
L23 affects RX and TX - because it's the Main IF mix BOTH sides (RX and TX) use...it's the 10.240 PLL main clock. So it looks to L24's output for the IF.
You "tune" L24 - which is another part of the Radios IF processing, it's 10.240MHz.
The Radio already generates a 10.7 IF signal by subtracting what L18 does...so L23 just peaks out what Delta Tune generates, as a varying correction signal
you control - against the main 10.240MHz crystal and
L24 as a
TUNED Circuit the PLL sees for it's main clock frequency to compare everything else to - from L22 and L19 and L18 thru and over to L23....
L24 ALSO is used (indirectly but thru L23) to develop
455kHz or the LAST IF (Final IF)...thru the "Delta tune" knob. It beats against the 10.7MHz IF signal -
subtracts from it - and leaves
455kHz for L7 (Originates at), L8 and L9 amplifies for the Detector and AF section to use...
Ok, Got IT? Don't worry if you didn't, it's a lot to think about - take your time - let's get back to our radio...
There are RX frequencies which the Radio uses to DECODE the CB frequencies and process them in higher and higher levels of gain and filtering without the complexity of large parts counts and complex circuit designs...
The next step is L18, it's your TP5 and your 16MHz to 17MHz signal - so once you know how L23 and L24 work, you'll see where L18 PEAKS the performance of RX side but only in the first stages of IF and RF amplification.
L22 is for L19 and L18 - but L22 is exclusive to the PLL and functions a loop oscillator to provide L19 and L18 signals - but it SAMPLES them to make sure they are what the Channel SELECTOR says they should be.
- To track this, the PLL lets' L22 run, but in the process of running, it needs a method of tuning resonance to make the L22 coil even oscillate - so it sees capacitance added as a means to make it resonate. This generates the oscillation "ring".
- To capture that energy, a special Mixer chip - AMPLIFIES this effect and reapplies it back into the loop - keeping the oscillation going.
- The Chip also BUFFERS the oscillation so the L19 and L18 can see the oscillator action so they can peak their response to and allow power to be branched off of them for the radio to process.
- The PLL samples this "Ring and Oscillation" and adjusts - tracks this event and adjusts the oscillator thru a VARACTOR.
- - L22 sees the Varactor as a capacitor
- - but the PLL uses the ability of the Varactor to change it's capacitance by sending it a small change in voltage being applied to this Diode.
- The PLL sends the Varactor this "error correction" signal and then continues to sample the loop and this process allows the PLL to take control of the Loop and the Oscillation - this process is called a "LOCK" - which is the ability for the PLL to control L22 as a Local Oscillator and keep the timing correct to make the proper IF signals to let the Radio change the Channels and provide Receive and Transmit is one package.
L23 - affects 2nd IF as well as the TX sections other half of signal L19 uses to make 27MHz...
L24 is the main Clock 10.240MHz - that both the PLL and Delta - Tune for your RX use.
The PLL also uses this Main Clock (L24) for timing AND tracking of it's own Loop at L22 and L19 - for TX but PEAKS L18 for use with Image for 10.7MHz IF Production (your 1st IF stage)
The PLL generates another signal that L19 and L18 use. But there is an important step the PLL does to change what L19's Signal does, and this affects L18's ability to provide a means to SUBTRACT a frequency it supplies to the 1st IF stage - so you obtain a 10.7MHz IF signal to process thru a stage that amplifies your Received CB signal, converts it thru a process of mixing - DOWN to 10.7MHz.
Remember - we have 455kHz signal that is the
Subtracted Image from 10.7MHz and the 10.240 Carrier signal the radio beats with, or mixes with - it the result of the 10.7 Downmix to make the
455kHz Image you hear for Receive, we don't need it - nor use it - for TX side...
So the PLL SHIFTS it's frequency and uses L19 and L23 together to Mix and combine to form a 27MHz carrier for the Pre-driver to use and sends that to the Driver and Final for transmitter output.
But what about L22?
L22 is the PLLs own oscillator that it runs and lets L19 and L18 look to, for sync with and provide peaking for amplified output the Loop provides the base 16 to 17MHz signal - only L22 is controlled by the PLL and so when you TX or RX - depending on the mode - the radio shifts its L22 frequency Up or Down
455kHz and the proper coils L18 or L!9 are used to generate, peak and select the channel frequency - the IF signals DERIVED from this mixing - is what carrier signals the radio uses to make the Images form in your Receiver to obtain the RF signals present of the channel you select.
This mixing stuff is not complicated, but then understandably the thought process to figure this out - it's how they have to make it work - is what makes this so confusing.- the routing nightmare...
The Process is called
Hererodyne - you mix two signals together - you get 3 products - thru a process of Addition, Subtraction to your Original signal - you can attain an "Image" of the Original - but at a different frequency that is above and below your ORIGINAL one...
This is a big post, so I'll have to let you read thru this and I hope it helps you understand the Radios Receive and Transmit and the Mixing process to make the two modes work.
