The uPD2824

The 10.240MHz xtal can easily be changed to something like 10.260 or similar to give a different range of frequencies. By far the best option for this radio is a simple external PLL (or VFO if  your so crude). 15-18MHz will give you a lovely wide ride TX/RX. You'd basically cut the track from the PLL mixer to the TX/RX mixers. There will be a driver  transistor at this point. Injecting the 16.27MHz signal will bring you into the band at ch1. You could also screw with the down mixing PLL feedback loop. This will be a easy to recognise by a low pass filter between the mixer and the PLL chip (pin 17). The signal is about 1MHz. Injecting a stable frequency into this pin of the PLL will also change the output accordingly. Injecting 445KHz will put you on ch15 NZ call channel. 1.445MHz will put you on 27.500MHz. Pin 20 changes the step size from 10KHz to 5KHz.

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C5121 or TC9109

These PLL's use a rather complex mixing system that makes them just simply a pain in the arse and not worth the effort of modifying.
They have internal ROM channel select that limits the choice of channels through the normal channel select.

I think this chip is what is used in the Pearce Simpson Cub or Lankar.
I had a mod for this chip, it seems to be pin 11 de-earthed, but it has no other notes to describe what it does. It's worth a try if you have nothing else to do.

The arrangement of this PLL in circuit is rather messy and frequency shifts are everywhere. Any modification to any part of the circuit like the 10.24Mhz crystal will result in wildly different frequencies.

The VCO is shifted down 3MHz for the TX frequency and released back to 16MHz for RX. If you wanted to xtal lock your radio onto one out of band channel, then you could have two xtal oscilators made, one 13Mhz and one 16MHz and inject the 13Mhz into the transmit doubler and the 16Mhz into the receive mixer.

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Ok, Another big name PLL chip. The uPD861

You are probably familiar with the mods for this PLL. Ground the "Mode Select" - Pin 14 !
If it is already earthed, then you're in business. Pins 1 to 8 are simple binary select.
If "RF Inhibit" pin 24 is connected, then cut the track.
That's the simple mod

Welcome to the big league.. The IF mixing scheme for this PLL is all messy and I can see no way of achieving any other frequencies by using a PLL, Sig gen or digiscan etc.
Instead this PLL has an interesting feature. It has two dividers, one is a reference divider the other is the program divider. This is what you normally program through pins 1 to 8. Nothing special there !
What is special is that in most PLL's these dividers don't have an output to the real world, instead the signal is processed internally and it pops out the arse end of the PLL as a DC voltage that you average garden gnome won't notice or care about. This tells the VCO what frequency it should be oscillating at.
This is your chance to rebuild part of the PLL for your own evil purposes. !
The reference divider is rather un-interesting and is probably best left alone, but what you do to the program divider, you can also do to the reference divider later. (Think of it like front and rear gears on your bicycle). The reference divider is probally only something small like divide by 2,3,4,5. Even a small change here will probably make a large difference in frequency, probably too much.
Baby steps people !
The program divider is a standard 8 bit, giving you 255 channels, though I'm lead to believe that the stock program divider doesn't allow the bottom 3 channels. The program divider input is Pin 18 and it's output is Pin 15.
Cut these tracks and you own program divider connects to the circuit board.
A 10 bit programmable divider will give you 1024 channels !!!

HOLY MOLY BATMAN ! THAT's OUTSIDE OF THE LOCK RANGE OF THE VCO AND THE PASSBAND OF THE FRONT END FILTERS !
Correct Boy Wonder ! All those extra channels have got this joker nowhere !

Yes, even the radio has its limits and 1024 channels does exceed them. And no, you can't broadband your front end to do 24Mhz ! Don't even think of touching those little metal cans !!

There is however some more good news. You can now go back to the reference divider and hopefully set the step size of the program divider much finer in comparison.
What this means is that instead of 1000 channels taking up 10MHz in 10KHz steps, we make those 1000 channels fit into 1MHz in 1KHz steps ! Much finer tuning.
(Example of being 1KHz off an SSB call channel with a carrier causes a 1KHz tone to be heard by all SSB stations.)

To complete the modification, unlock the clarifier for TX or if it doesn't have one, look for the reference crystal. Not the 10.240MHz or 9.785MHz xtals ... the other one !

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The uPD858. Pretty awesome little chip this one....

If you're a novice at extra channels, this is one of the easier chips to hack Go straight to the BCD pins and dial up the channel of your dreams. Start with pin 4 for 10/5KHz steps. Easy Pins 13,14,15,16 control the ones channel. i.e. 1,2,3,4,5,6,7,8,9,0 Pins 17,18,19,20 control the tens, i.e. 10,20,30,40,50,60,70,80,90,00 Pins 21 ans 22 are the hundreds. you only have the choice of  000,100,200,300 So in total, you have 400 channels to pick from and their half channels. Why you'd modify this radio in any other way is beyond me. Maybe you just have nothing better to do.

Procedure same as uPD2824....

You could also screw with the down mixing PLL feedback loop. This will be a easy to recognise by a low pass filter between the mixer and the PLL chip (pin 5). The signal is about 1MHz. Injecting a stable frequency into this pin of the PLL will also change the output accordingly. Injecting 445KHz will put you on ch15 NZ call channel. 1.445MHz will put you on 27.500MHz. Since The PLL mixer is mixed in with the SSB circuit, it is advised not stuff around with it. You could inject 35MHz from your own PLL or VFO if you know where to look. It is even possible to make use of the on board 35MHz VCO and let your own PLL drive it. But this is for the more technically advanced of you.

Mod sent in by Trash