Motorola Alert Monitor

[N3hzz]

I have an Alert Monitor reciever that I wish to re-crystal. It is currently at 154.400. and I am trying to find the forumulas to prove this by crystal frequencies. Does anyone have that information handy? I know its a blast from the past but that is the fun of it.

[Tom in D.C.]

As I recall, I think it was the "standard" fmHz - 10.7mHz/3 for the crystal.
I also recall that these things were quite sharp and somewhat difficult
to tune. Let's hope someone jumps in an either confirms or corrects
my crystal formula. Is the crystal now in the radio marked, hopefully, 47.9 mHz?

[Jim202]

It has been around 20 years since I played with one of those. but I think you have the correct numbers
to figure out the crystal freq.

Jim

As I recall, I think it was the "standard" fmHz - 10.7mHz/3 for the crystal.
I also recall that these things were quite sharp and somewhat difficult
to tune. Let's hope someone jumps in an either confirms or corrects
my crystal formula. Is the crystal now in the radio marked, hopefully, 47.9 mHz?

[N3hzz]

As I recall, I think it was the "standard" fmHz - 10.7mHz/3 for the crystal.
I also recall that these things were quite sharp and somewhat difficult
to tune. Let's hope someone jumps in an either confirms or corrects
my crystal formula. Is the crystal now in the radio marked, hopefully, 47.9 mHz?

Thanks for the replies. The two crystals are: 12155.00 and 13540.00. I used to work at a MSS shop, but I can't find my manual.

[Andy Brinkley]

The 12.155 mhz crystal is for the IF (12.155-0.455 = 11.7 mhz)

From my manual for the L03CND models (circa 1975) the crystal formula is

F01 = (FC -11.7)/10

(154.400-11.7)/10 = 14.27 mhz

The 13.540 crystal shoud give you a 147.100 receive if my calcs are correct.

What frequency are you trying to find? I have a pile of the crystals for them somewhere.