1 upvotes, 1 direct replies (showing 1)
View submission: Question about BH1415F Pre-Emphasis
Mine has through hole components not smd and i would like someone who knows to tell us the values of components for 50us and 75us preemphasis. I dont know if now is running on 50 or 75 an so i want to check because i am in Europe. I am running it on 50mw power! Just for home use!
I just found on the manual of Ramsey FM25b which also uses bh1415f that the capacitors are 2200pf for 50us and 3300pf for 75us!
I had a transmitter in the past that not worked at all when i removed the 1nf caps and kept only the 50k resistors. I tried that so i could have external pre emphasis and audio processing. The transmitter was a Ramsey Fm110b with analog stereo coder and vco/pll on the same board! Great unit but i shorted it some way and i cannot find the same any more. It was engineered by John Ramsey. Great little unit delivering 15 watts on high power using a mosfet on the output.
Comment by KubaPro321 at 21/01/2025 at 13:16 UTC*
1 upvotes, 1 direct replies
use 50, if in usa or south korea then 75 (looks like some misinterpret this, use 50 generally, 75 when in usa, )
and to calculate which capacitor values you need, you have to ack that the bh1415f has 22.7 kOhm resistors for preemp, and to calculate tau you do 22.7kOhm*Capacitance, so if you have 2200pf then its 22.7kO * 2200 pF (22700*(2200*10**-12) in python) which is 4.994e-05, so 49.94 micro but if you have 3300 then its 7.491e-05 (74.91 micro),
also you didn't have the same problem, i wanted to get rid of it and since i had switchable preemphasis i just poked the leg of the chip and capacitor with a multimeter and listened for a beep