# Interchanging Crystals

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#### steelbeak

##### Member
I have a Bearcat III H/U which uses 10.8 IF crystals.

I have a crystal marked "460.425MHz MRU-1" which I interpret as being a 10.7 IF crystal used to receive on a frequency of 460.425MHz.

Can I put this crystal into the Bearcat III and if I can what frequency should I receive in the Bearcat?

My initial assumption was that if I subtract 10.7 from the frequency, then divide by 9 I would get the crystal's real frequency. And then armed with this value I could find out what its UHF frequency in the Bearcat would be (460.525MHz).

Does that sound right? Or does the fact that it's a 10.7 IF crystal change something in this equation that I'm missing?

And to answer the first half of my first question I tried putting the crystal into the Bearcat and, by some arcane magick, is currently picking up traffic off a local repeater. However the repeater (as far as I'm aware) is a high band frequency and not UHF, so I shouldn't be picking it up in the first place.

And I have check at least a dozen times that the crystal is plugged into the UHF module and not the high band module.

#### w8jjr

##### Member
Yup

460.425MHz >> 460.525MHz

Use to interchange them all the time.

10.7 IF crystal cut for 155.010 will
resonate at 155.110 in a Bearcat. Close enough for the 155.115 PS Freq.

subtract 0.10 for 10.8 IF crystal
155.010 will resonate at 155.000 in a 10.7 xcvr

I have a Bearcat III H/U which uses 10.8 IF crystals.

I have a crystal marked "460.425MHz MRU-1" which I interpret as being a 10.7 IF crystal used to receive on a frequency of 460.425MHz.

Can I put this crystal into the Bearcat III and if I can what frequency should I receive in the Bearcat?

My initial assumption was that if I subtract 10.7 from the frequency, then divide by 9 I would get the crystal's real frequency. And then armed with this value I could find out what its UHF frequency in the Bearcat would be (460.525MHz).

Does that sound right? Or does the fact that it's a 10.7 IF crystal change something in this equation that I'm missing?

And to answer the first half of my first question I tried putting the crystal into the Bearcat and, by some arcane magick, is currently picking up traffic off a local repeater. However the repeater (as far as I'm aware) is a high band frequency and not UHF, so I shouldn't be picking it up in the first place.

And I have check at least a dozen times that the crystal is plugged into the UHF module and not the high band module.