NOTE: Although I would like to take credit for this modification, I must give credit where credit is due. Sue Nguyen is the person responsible for figuring this out . She is a technician extraordinaire, and her knowledge is second to none. In addition, she is a really great person. Sue, thanks for all of your help on this mod. - 399
The UNIDEN PB-010 chassis was marketed as the Cobra 148GTL-DX Mark II and the Superstar 360fm.This modification applies to them and to many other export radios that use the MC145106 PLL.
This modification does not permit the radio to switch channels in 5kc steps. However, it allows the installation of a "5kc jump" switch, which gives the user the "zero" channels (i.e. 27.400, 27.410, etc.) without changing the position of the clarifier.
Moving all of the PLL PD lines over by 1 pin is binary multiplication by 2. In other words it doubles the "N" value. Each pin is now shifted by twice as much. BUT putting the PLL into the 5kc mode DIVIDES the "N" value by 2, so that each pin is now shifted by exactly the same amount as it was before the mod. The radio will now operate over the same frequency range as it did stock. There is ONE difference though. Pin 17, which adds "1" to the "N" value (increasing the output frequency by 5kc) is no longer connected to the channel selector.
Now if we connect pin 17 to 5V through a switch, the output frequency will increase by 5kc. For instance, channel 40 mid band will "jump" from 27.405 to 27.410 at the flick of a switch. Connect switch S1 as shown in the diagram above to complete the PLL portion of the mod.
Unfortunately, this mod may permit some phase noise to make it through the PLL loop filter, allowing an annoying whistle on AM and FM, as well as distorting SSB audio. To prevent this, the cutoff (corner) frequency of the loop filter needs to be reduced by about 50%. On the PB-010 chassis this can be done by changing the value of R126 from 27K ohms to 36k ohms.
With more operators using the "zero" channels on SSB, this is a quick and easy way to get them on the PB-010 chassis.
- 399
The UNIDEN PB-010 chassis was marketed as the Cobra 148GTL-DX Mark II and the Superstar 360fm.This modification applies to them and to many other export radios that use the MC145106 PLL.
This modification does not permit the radio to switch channels in 5kc steps. However, it allows the installation of a "5kc jump" switch, which gives the user the "zero" channels (i.e. 27.400, 27.410, etc.) without changing the position of the clarifier.
First up, make these 4 changes:
1) Isolate all of the PLL programmable divider pins (9 through 17 inclusive) by cutting the PLL traces as close to the pins as possible
2) Connect them back up with wire jumpers as below:
- Connect the trace that went to pin 17 to PLL pin 16
- Connect the trace that went to pin 16 to PLL pin 15
- Connect the trace that went to pin 15 to PLL pin 14
- Connect the trace that went to pin 14 to PLL pin 13
- Connect the trace that went to pin 13 to PLL pin 12
- Connect the trace that went to pin 12 to PLL pin 11
- Connect the trace that went to pin 11 to PLL pin 10
- Connect the trace that went to pin 10 to PLL pin 9 .
3) Put the PLL into 5Kc mode by connecting pin 6 to ground.
4) Install a 5.1k ohm resistor between pin 17 and ground.
1) Isolate all of the PLL programmable divider pins (9 through 17 inclusive) by cutting the PLL traces as close to the pins as possible
2) Connect them back up with wire jumpers as below:
- Connect the trace that went to pin 17 to PLL pin 16
- Connect the trace that went to pin 16 to PLL pin 15
- Connect the trace that went to pin 15 to PLL pin 14
- Connect the trace that went to pin 14 to PLL pin 13
- Connect the trace that went to pin 13 to PLL pin 12
- Connect the trace that went to pin 12 to PLL pin 11
- Connect the trace that went to pin 11 to PLL pin 10
- Connect the trace that went to pin 10 to PLL pin 9 .
3) Put the PLL into 5Kc mode by connecting pin 6 to ground.
4) Install a 5.1k ohm resistor between pin 17 and ground.
Moving all of the PLL PD lines over by 1 pin is binary multiplication by 2. In other words it doubles the "N" value. Each pin is now shifted by twice as much. BUT putting the PLL into the 5kc mode DIVIDES the "N" value by 2, so that each pin is now shifted by exactly the same amount as it was before the mod. The radio will now operate over the same frequency range as it did stock. There is ONE difference though. Pin 17, which adds "1" to the "N" value (increasing the output frequency by 5kc) is no longer connected to the channel selector.
Now if we connect pin 17 to 5V through a switch, the output frequency will increase by 5kc. For instance, channel 40 mid band will "jump" from 27.405 to 27.410 at the flick of a switch. Connect switch S1 as shown in the diagram above to complete the PLL portion of the mod.
Unfortunately, this mod may permit some phase noise to make it through the PLL loop filter, allowing an annoying whistle on AM and FM, as well as distorting SSB audio. To prevent this, the cutoff (corner) frequency of the loop filter needs to be reduced by about 50%. On the PB-010 chassis this can be done by changing the value of R126 from 27K ohms to 36k ohms.
With more operators using the "zero" channels on SSB, this is a quick and easy way to get them on the PB-010 chassis.
- 399
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