China made Cobra 148gtl clarifier problem.

[kopcicle]

Full channel one way and 7 or 8kc the other.

Ever try to use a clarifier with that kind of range in a mobile?
Let's look at that for a second...
For a range of just 1500 (because the numbers are easier)
Most fine tune poteniometers are 270 degree span.
That's > 5.5 Hertz/degree.
The outer circumference of the knob is close enough to 1.5" and...
The painted line on the knob averages .045" so..
.001= 1 degree = 1 Hertz = a possible range of error of 90 Hertz.

Texting and driving ?

Lets over simplify and cut that range in half.

.001= 1 degree = .5 Hertz = a possible range of error of 45 Hertz.

Compare that with the stock range (close enough)

.001= 1 degree = .25 Hertz = a possible range of error of 23 Hertz.

If you need the alphas do it to the chip. if you need the zeros switch in some "c".

When you get tired of all this parts in, parts out, drifty crap just put a DDS in it and tolerate the phase noise.

TANSTAAFL YMMV

 

[sonoma]

I do not like one to slide that much either Kopcicle.

 

[sonoma]

999 what are you doing to get this much slide out of one. look at the info I left early on for the clarifier mod

 

[999]

It's been forever since I did one, but I just followed the published information.
I also read that you can't switch jump the mmb8719, but that worked on that China radio I did last, so I have no clue.

 

[sonoma]

are you talking about the 10kc jump for the PLL to get the alpha channels.
the reason I am asking a few guys I know would like to drop to the zero channels at times .

 

[American-Vulture]

thanks for the diagram.it will certainly straighten out my crooked mind.
If this works I will reward you.

 

[sonoma]

American Vulture you have the diagram pl;us the writing just above it to help you mod the radio.

 

[999]

are you talking about the 10kc jump for the PLL to get the alpha channels.
the reason I am asking a few guys I know would like to drop to the zero channels at times .

No. The clarifier will slide the 10kc.

 

[American-Vulture]

I seem to not have ground on the board.i have source voltage but no connection to the places on the board that's supposed to be ground.Checked screws everything.
Getting ready to throw this thing in the trash.cobra 148
radio is totally dead..

 

[Shadetree Mechanic]

I seem to not have ground on the board.i have source voltage but no connection to the places on the board that's supposed to be ground.Checked screws everything.
Getting ready to throw this thing in the trash.cobra 148
radio is totally dead..

Maybe something in the voltage regulator area went out?

 

[American-Vulture]

Its alive again!!!!! Found a wire that was completely missing on board!
PA works,channel and TX & RX led changes with mic keying.
Heres comes round two.Yup it would be easier just buying a good one but
it feels good bringing something back from the dead.Just look at me!

 

[kopcicle]

Just look at me!

 

[ExitThirteen]

Looks like you got the Kop's attention...


~Cheers~

 

[American-Vulture]

Any ideas where to start looking?I am getting 25.9070 on all channels.
Could it be a bad PLL chip?

 

[American-Vulture]

Its alive again!!!!! Found a wire that was completely missing on board!
PA works,channel and TX & RX led changes with mic keying.
Heres comes round two.Yup it would be easier just buying a good one but
it feels good bringing something back from the dead.Just look at me!

Now it croaked again.All channels at 25.9100.