Motorola Alert Monitor Information

[hvfcadmin]

I have about 20 Of these Minitors, UHF 2-Tone (M04CNB1102B) Freq 453.3250Mhz

1st Question - Does anybody know what part ZLN6184A is used for ?? (1" x 2" board installed on side of Tone decoder Board).

I'm in the process of Bringing back to life all of these monitors that are in various stages of repair, I have one that is working perfectly that i use as my "Golden unit" for comparison. There really isn't much Information on these any more. Does anyone have a manual or schematics that covers the model i'm working on, or any of the models for that matter? It's very time consumming reverse engineering the boards myself but very interesting. So far ive got the tone decoder board done (NLN4370A), Power supply section done and starting on the RF front end. I have all of the various test equipment needed to do pretty much anything RF relaited, but will need some pointers when I get to the Allignment.

It would be nice to have a section just for Motorola Allert Monitors, the batlabs page really doesnt have a whole lot of info. Kind of like a place that would have Part Number info, Model Number info, Options, modifications, repair tips, Part cross and pictures. sort of like the Spectra page on repeater builder. Electronics has been my life long hobby so spending countless hours working on stuff like this fun for me, There's allways something new to learn.

Yes, i know there OLD but I have a liking for the older vintage motorola gear.

I'm sure there is a lot of people who would find this information usefull.

If anybody can help just email or PM, i would greatly appreciate the info

PS. if any body needs any service manual info for the spectra series, I have quite a few, I would be happy to help if needed.

[hvfcadmin]

Would anybody know the crystal calculation formula for the VHF and UHF Monitors.

The UHF is on 453.3250Mhz
Crystal 1 inside toward back is marked 18207.50 (18.20750Mhz) ?
Crystal 2 inside toward middle is marked 16800.00 (16.800Mhz) ? Possibly IF freq? (GN & 851 marking on side)

The VHF is on 155.0100Mhz
Crystal 1 inside toward rear is marked 14243.00 (14.24300Mhz) ? (AN & R8850 marking on side)
Crystal 2 inside toward front is marked 11245.00 (11.24500Mhz) ? Possibly IF Freq? (G22 marking on side)

[Andy Brinkley]

The crystal formula for the VHF Alert Monitors is
Crystal 1 * 10 + 11.7 (IF frequency)

using your numbers, 14.243*10 + 11.7 = 154.1300 mhz

I'll have to dig out the UHF manual to get the formula for them

[RogDog]

The ZLN-6184A is a reset timer. It is used to automatically reset the monitor after it responds to a two-tone or QCII tone out which causes the decoder equiped monitor to alert. I would be very interested if anyone has a copy of the service sheet on this device.

[hvfcadmin]

I don't have the official Service sheet, I just reverse engineered the pcb board and drew up the schematic. The devise is pretty simple, just puts out a square wave of given Freq, Time Hgh = reset period.