mb8719 pll 10k (able's) switch - uniden grant/ cobra 148

[Carl]

just a quick question about when adding a 10k switch to the mb8719 pll in a grant or 148. you seperate the trace to pin 16 off the pll and add a 4.7k ohm resistor across the bridge do i switch 5v or 8v to make it jump 10k, the internet is no help as all as different sites say different things. if its 8v thats easy as i will just pull from pin 9. its been 9 years or better sence i modded a grant.

i had a brand new grant xl (phill) in the attic at my moms so i figured i might as well use it. i did the channels and a peak and tune as well as a blue light bulb cover and a blue channel display but want to do the 10k for now.

 

[nomadradio]

Center-off switch, center pin of the switch goes to pin 16 on the 8719. One side of the switch goes to ground, the other side to 8 Volts. Easiest place to get it is pin 9 of the 8719.

The idea is that with the switch in the center position, the new switch does nothing.

There is no way to put a nice, easy "Plus Ten kHz" function onto that PLL chip. On channels where pin 16 is low, flipping the center-off toggle to the +8 side moves you up one channel. On channels where pin 16 is high, flipping it to the ground side moves you down one channel.

Can never remember which, but on two of the "RC" frequencies that get skipped by the channel selector, you go to the channel above, and flip the switch down. On the other three, you go to the channel below the "RC" and flip it the other way to go up one.

On a channel that has an "even" binary code (pin 16 low), flipping the switch to ground side doesn't change anything. Likewise on a channel with an "odd" binary code (pin 16 high), flipping the switch to the +8 side changes nothing. All you can do is drive the pin to the OPPOSITE binary value the channel selector is already feeding it on that channel.

A frequency counter, or display is a big help in getting this straight.

73

 

[Carl]

thank you, i remembered it was 8v. im just doing the +10k so i can do most of them and 19a thats the only common one around here, well that and i dont drill holes or add switches to my radios so its going on the cb/pa switch as the hi/low tone and brt/dim switches are controlling the extras. i like them to look stock, this one i had to change to blue as it is my indoors radio.

 

[bushwacker]

The idea with doing the 10 k up and down with a center off switch is that you will be able to get all the "A" channels
Like Nomad was saying, you will not be able to get all the "A" channels by just "jumping up" 10 kc..... for half of the "a" channels this will be fine, but for the other half you need to jump down (or vice versa, I can't remember)... but the idea is for channel 3a you can only get to it by going to channel 3 and jumping up 10kc... if you wanted to go to 7a you will not get it by going to channel 7 and jumping up 10kc.... it won't work... you have to go to channel 8 and jump down 10 kc
For some channels you have to jump up and for others you have to jump down
So it might be worth considering using a center off switch and doing both the 10kc jump and drop-- its not much extra work... only a wire to groundAlot of times this 10kc jump "mod" doesn't turn out the way people expect
Sounds like you have everything planned out
Take care