Model Boat Mayhem

Technical, Techniques, Hints, and Tips => Radio Equipment => Topic started by: Timo2 on March 14, 2009, 08:54:11 pm

Title: Crystal Type ???
Post by: Timo2 on March 14, 2009, 08:54:11 pm

Hi All

  Can you help me    40Mhz Crystal types

        FM rx 40.985  ( 92 Black ) ( Code Type 40-12 )     Works OK.    :-))

        FM rx 40.985  ( 98 Blue )  ( Code Type 27-2 )       No go   <:( <:(

    Why  you clever lot

     Please help the old one

    Timo2

Title: Re: Crystal Type ???
Post by: maninthestreet on March 14, 2009, 09:20:17 pm

what make are the crystals, and what make is the equipment you are using them with??

Title: Re: Crystal Type ???
Post by: Timo2 on March 14, 2009, 10:53:23 pm

Hi Maninthestreet

     Cirrus 

    All FM Type 

     Tx    4+1 Jamara                Rx   1 Jamara  , 1 Hytec , &  4  Sunip ,

       Tx on FM 40.985              All Rx  work on  FM 40.985  ( 92 )

    Timo2

Title: Re: Crystal Type ???
Post by: Shipmate60 on March 14, 2009, 11:03:10 pm

Timo2
I have several Cirrus receivers and use Futaba crystals with no problems at all.

Bob

Title: Re: Crystal Type ???
Post by: maninthestreet on March 14, 2009, 11:12:45 pm

Perhaps the crystal that doesnt work is a dual conversion crystal?

Title: Re: Crystal Type ???
Post by: Timo2 on March 15, 2009, 11:26:49 am

OK

     Two types but what is what {:-{

 Timo2

   ( Ripmax web site no ******* help  >>:-( )

Title: Re: Crystal Type ???
Post by: malcolmfrary on March 15, 2009, 11:58:18 am

Because of the way that radio receivers work, the RX crystal frequency will be offset from that of the TX by about 455KHz.    The crystals are normally marked with their actual resonant frequency, so you have to trust in the channel markings if these are there. 
I did once run into a case where the crystals were wrongly coded - it was resolved by a pegboard marshal who had a scanner, and figured out who had the crystals with the dud information on.
The most reliable way of testing for those without test gear is by substitution - get hold of a mates known working crystals and see where the problem goes - does it stay with the equipment or follow one particular crystal?