¿HOW CAN I CHANGE THE AUDIO SUBCARRIER IN A SAT92 RECEIVER?
two components must be replaced: quartz crystal and audio filter.
the audio subcarrier frequency of this unit is controlled by a crystal according to the following relation:
audio intermediate frequency: 10,7 mhz
audio subcarrier frequency desired: f mhz
crystal frequency = 10,7 mhz + f (audio subcarrier frequency) mhz
audio subcarrier frequency desired: 7,02 mhz
then crystal frequency = 10,7 + 7,02 = 17,72 mhz. this is the frequency of the quartz crystal to be ordered.
on the other hand it is necessary to change the audio filter by a narrow one (bw=150 khz), televes code:136700.
note: by default, the audio is set from factory as follows:
audio subcarrier 6.5 mhz (crystal frequency is 10,7+6,5= 17,12 mhz)
audio filter bandwidth: wide (280 khz)
please follow teh next instructions to make the change:
arrangement of components in your unit may differ slightly from the layout of teh figure.
anyhow both crystal and ceramic filter are quite easy to find, more or less in the vicinity of the positions indicated.
please do not touch any other component unles those specified.