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858PLL 23 Ch. to 40 Channel "update".

LeapFrog

LeapFrog

Wielding Hanlon's Razor
Feb 15, 2016
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Anchorage, Alaska
Hello I have a Cobra 21x (Uniden PC-169AB) with the "D858" PLL, I really want the entire 40 channels for this radio.
It's hard to see but I marked pin 1, and pin 24.
[photo="medium"]4340[/photo] .

Here is a "guide" I found. EDIT: It says 858 CHASSIS, I'm screwed ATM lol, data sheet 'oh where art thou?

The radio I plan on modding contains a PLL can, my question is does this look right before I start cutting traces because it looks like they used a schematic from a radio that had a (main)board mounted PLL?
[photo="medium"]4343[/photo] .
Any help would be greatly appreciated, should I just isolate pins 19/21 entirely and then proceed with the secret cb guide?.
Thanks
-Leap
 
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This is as far as I got.
[photo="medium"]4344[/photo] .
I combined the wires @ 21 & 20. My PLL area doesn't look like the "guide", i'm going to wait before testing, someone please let me know what you think. The lower portion of the photo shows the two points I have combined (marked with a red line).
 
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well Leapfrog I have never tried to add extra channels to this 858 PLL radio. so not sure just what you need to do. the page you left a link to is for a 858 40 channel radio to add channels above and below the regular 40 channels. I will look around on the web to see if I can find the mod for the 23 channel. maybe some one else has done this to a 23 channel radio.
 
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A datasheet for this PLL would be the ticket then the guess work goes bye bye, I believe it's some kind of mod to set a pins "logic" to a high state (5v+) when the switch (diode matrix) adds/removes the right amount of resistance in the circuit.

I found another page dealing with this pll, I just have to find it again.

Worst comes to worst I will copy the diode matrix and PLL area from a similar (but 40 ch.) radio.

Thanks Again
-Leap
 
Now that it's sitting on the desk and wired to the six position & dpdt switches I no longer have an unused connection o_O, been a long day lol.

I need to bench test this before completely reinstalling it.
If anyone has any advice/knowledge/tips please share.

-Leap
 
That's what I plan on doing triple checking all the connections before applying power, I need to continue to cross reference 858 PLL against 858 chassis as I may have the wrong information for this mod!
Thank you Robb
 
That UPD858 PLL is a binary coded decimal (BCD) type. When looking at the pll chart in your link above you read the the pll input pins from right to left. 3a and 3b are the first digit in the n number while 1a 1b 1c 1d form the last digit. In BCD each real digit is represented by a binary group. Other PLLs simple step in normal binary progression 1 2 4 8 16 etc.
 
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Years ago I once did a mod for a blind operator. I installed switches on the bottom of the radio (base model) and taught him binary. He could QSY anywhere by the feel of the switches. Up was 1 and down was 0.
 
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I bought a TRC-452 for 25$ (PC-170), now all I need to do is swap the channel selector switch (as the pll pcb/ schematic matches between the 23 ch. and 40 ch. radios.)
..Oops I may just move the whole pll unit with the channel selector switch.
from a link below: Indeed, the later 40 channel version (The TRC-452), was virtually identical to the '152 with the exception of the channel switch and a wider bandwidth VCO block in the PLL section.
Click to expand...

I'm going to swap the channel select knob over also to complete the "factory style" 40 channel conversion for the 21x, and re-install the 23 channel knob/pll can on the TRC-452. (One day I may put one of these on 10/12 meters but for now the trc will sit in a closet after testing).

I figured this out after finding this page and comparing the schematic diagrams between the TRC-452 and the 21x they are virtually identical. What I like about this compact Uniden chassis is that they didn't use an audio IC, so this leaves an open area to experiment with A.F. clippers and other mods in.

I am going to examine the RF gain and TX/Mod LED configuration on the Realistic ( as these "features" didn't come on the 21x) and copy it/mod it over to the Cobra 21x (which has the mic gain "feature" that the TRC-452 lacks :)).

Depending on how long it takes for the radio to ship to me, I will eventually come back and post my results.

Best Regards.
-LeapFrog
 
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