Hi guys. I build a FM transmitter based on the ba1404 chip. The problem arises because this chip need a 38Khz crystal for produce a subcarrier signal for the stereo transmition, but that crystal is hard to find. To solve it i programed a PIC16f84 to generate the 38 Khz signal and, depending of what crystal use for the PIC, i could reproduce the 38Khz fecuency more or less exactly. (For example wuth a PIC runing on a 4MHZ crystal a can generate a 38,4 Khz signal). What accurate such signal have to do?
The accuracy should be either in the part data sheet or in the relevant communications frequency specifications. Note that transmitters are regulated by law in almost all areas of the world and so you may NOT go by seat of the pants "I think this should work approach". You need to research the authoritative literature and get proper information so that you can design correctly. In most cases your transmitter will have to be tested and certified compliant to regulations by an approved agency or testing laboratory.
"mkaras" "gula" Hi guys. I build a FM transmitter based on the ba1404 chip. The problem arises because this chip need a 38Khz crystal for produce a subcarrier signal for the stereo transmition, but that crystal is hard to find. To solve it i programed a PIC16f84 to generate the 38 Khz signal and, depending of what crystal use for the PIC, i could reproduce the 38Khz fecuency more or less exactly. (For example wuth a PIC runing on a 4MHZ crystal a can generate a 38,4 Khz signal). What accurate such signal have to do.
The accuracy should be either in the part data sheet or in the relevant communications frequency specifications.
** Nonsense.
Note that transmitters are regulated by law in almost all areas of the world and so you may NOT go by seat of the pants "I think this should work approach".
** Not fea powered ones like the BA1404 - d*****ad.
You need to research the authoritative literature and get proper information so that you can design correctly. In most cases your transmitter will have to be tested and certified compliant to regulations by an approved agency or testing laboratory.
** Go find out what a BA1404 is before you make an even bigger ass of yourself.
BTW
I have answered to OP's multi-posted query on another NG.
I think the OP wants to know how accurate the 38kHz frequency needs to be - although he's building a low powered Tx[1], it still has to work with commercially available receivers.
Will the average Rx work with this offset? (I don't know the answer but I was considering such a device myself and the question has already crossed my mind - so one answer might keep two people happy!)
[1] Although the RF part of such devices is regulated, as you say, I don't think that such regulation extends to stereo subcarrier frequency inaccuracy!
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.