Minitor III/IV - Need help on how to modify Band Splits

[n6fnp]

I am trying to find information on changing the band split on a Minitor IV pager. I'm able to change the band split using Engineering Mode in the
programming software, but it doesn't receive on the programmed frequencies. I've done a lot of Internet searching and found references to
having to adjust the VCO to lock on the new frequency, but have not been able to determine where to adjust the VCO. I have a Minitor 3 and 4
service manuals. One shows the board components, but I can't see where the VCO adjustment is done.

If anyone can let me know how to complete the process of changing the band split, it would be greatly appreciated!


-N6FNP

[rainbowpenguin]

Going off of memory -- there's a small hole in the metal shield over the vco. While transmitting on your desired frequency, hold the monitor button on the pager to open the squelch, and adjust the small trim pot/cap inside the hole for maximum quieting. There's a more exact process using a service monitor, but this'll get you pretty close.

How far from original bandsplit are you trying to adjust it?

[n6fnp]

Thanks for the reply. I have attached an image of the RF board. The only capacitor that I see that is under a shield is C210. Is that the VCO
adjustment?

If anyone can tell me what the other adjustments (C105, C305, C208 and C109) do, it would be very helpful.



I have a UHF Minitor 4 in the A8: 465-480 MHz range that I would like to change to work on the UHF 440 MHz Ham Band. Can a shift of that
large of a range be done if more than just the VCO is adjusted or would this require board level component changes?

[rainbowpenguin]

I've only moved 151.x to 147.x; a few pagers needed adjusting in order to work, and C210 (under the shield) did the trick.

Try it and see what happens?

[DJP126]

Movig from 465 to 440 won't happen. That's way too far off. You need a different rcvr board in that pager.