• You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
  • Click here to find out how to win free radios from Retevis!

23 ch 02a channel mod


I saw somewhere there was a mod to get lowers. Just asking
Actually there's a mod for lots of different radios that used this chip. It was popular with more than one factory. The tricky part is which mod works for your radio? Starts with knowing which radio model.

Needless to say, different factories chose different setups for this chip. The binary number that comes from the channel selector into the PLL chip will be different for different years' production circuits.

Simple AM radios used this chip with three quartz crystals in the radio, total. This seemed like a big savings compared 14 crystals or more in a 23-channel conventional CB.

Later they figured out how to do it with only two crystals. Needless to say, the internal arithmetic for the 3-crystal radio is not the same as in the two-crystal PLL circuit.

The exact change to be made for a chosen frequency range depends totally on those seemingly-arbitrary differences in the binary arithmetic that you modify to add channels.

So, is this about a particular model? Or just a wish that one 'universal' mod would work no matter which radio?

Ain't none of them.

73
 
Cybernet used three main configurations (there may be more) for the 02a chip.

AM 3 crystal, with PLL N-codes starting at 224 for channel 1 and going up to 253 (23 channel) or 268 (40 channel).

AM 2 crystal, with PLL N-codes starting at 330 for channel 1 and going down to 286 for channel 40.

SSB, with PLL N-codes starting at 255 for channel 1 and going down to 211 for channel 40.

So that's a completely different mod for each of them if you intend to put switches on the PLL programming lines because in each case the N-codes to get lowers are going to be different.

Say you wanted to put your radio on 26.815 MHz. For the AM 3 crystal chassis, you'll need to feed the PLL an N-code of 209. For the AM 2 crystal chassis, it would be an N-code of 345. For the SSB chassis it would be an N-code of 270.

This is why no one can provide you the answer you're looking for without knowing which radio you intend to modify.
 
Kraco 2330. Sorry I haven't been on here lately. Life and loved ones are more important than radios right now
 
Kraco 2330. Sorry I haven't been on here lately. Life and loved ones are more important than radios right now
I believe thats a ptbm039aox

 
Last edited:

dxChat
Help Users
  • No one is chatting at the moment.
  • dxBot:
    Greg T has left the room.
  • @ BJ radionut:
    EVAN/Crawdad :love: ...runna pile-up on 6m SSB(y) W4AXW in the air
    +1
  • @ Crawdad:
    One of the few times my tiny station gets heard on 6m!:D
  • @ Galanary:
    anyone out here familiar with the Icom IC-7300 mods