PLL02A channel Mod info????

[Techno1]

On the cybernet PLL02A ssb chassis is there a way to broadband the vco for a better range of extra channels.
I have from 28.045 down to 26.645. Has the potential of more lower channels but would have to alter the vco and
would loose some of the higher channels.
The vco as most of you all know is in the big marked ZZ oblong can.
I know I think you can get inside and mod it but tricky or buy 1 newer one from microchipz.

So is there a part near the vco that can help a bit more if changed out?
Also here is a picture of the large can VCO

 

[nomadradio]

Haven't looked at the diagram for that one, but I can offer a possible limiting factor. The PLL's VCO gets mixed with a crystal. The difference between those two frequencies is low enough for the PLL to keep up with. Max input frequency for the PLL02 is around 3 to 5 MHz IIRC.

Between the mixer and the PLL chip's input is a low-pass filter. Rejects all the higher frequencies being mixed, so only the difference frequency reaches the input of the PLL chip. That filter can become a limiting factor if you push the chip's input frequency too far below or above the designer's intent. If the output level from this filter into the PLL's input pin falls below the chip's lower limit, it can become twitchy.

All Cybernet radios are not created equal in this respect.

73

 

[Techno1]

Hi Nomadradio

Thanks for the info can that filter be removed and bypassed will it help?
Here is the schematic of the 02Aa and the mixer. can u point out the filter.

I cant see any good these days as I have acquired 2 Cataracts in my eyes that will be soon operated on to have new lenses inserted. In about 5 weeks been taking eye drops so there will be no infection after having the eyes done. Its the small print like this that gets blurry if I stare. I tried to find the filter but could not.

thanks for your help and info in this project. I will explain and post some other pictures later when im finished with this project of mine.

I also see that microchipz sells a replacement for the ZZ vco its about $10.00 but shipping will add to that big time.