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FM30
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as it is line level. Anything other than line level audio will sound distorted and
cost you time troubleshooting a non-existent problem. NEVER connect the
FM30 audio inputs to speaker outputs of a high power stereo system; such a
connection will destroy the IC chip. Trust us when we say that a true line level
audio source will give you the best results with your FM30.
The default volume setting is roughly ½ of full, which is a gain of 1. The means
that 500mV peak audio coming into the FM30 is 100% modulation, typically,
depending on frequency. The volume display also includes the clipping detec-
tor status and you should adjust the volume until the indicator toggles from ‘-‘
to ‘g’ occasionally, roughly a 50/50 timing between the two, with an occasional
‘c’ mixed in. If the character is always at ‘-‘, the modulation is too low, and if ‘C’
ever shows up (capitol) it means you are overmodulating. It’s best to set your
level up or down until you see the lower case ‘c’, which means that you're on
the edge of clipping. If you see the lowercase ‘c’ it means that you’re distorting
a bit so if you want to avoid that completely, make sure you set the level so
that you only see the ‘g’. Of course you can simply adjust the volume until it
sounds right to you.
The order of characters is approximately on average:
‘-‘ <= +/-60kHz
‘g’ >+/-60kHz and <+/-75kHz
‘c’ >+/-75kHz and <+/-90kHz
‘C’ >+/-90kHz
Remember from the circuit description that the indicator doesn’t specify the
exact level, but the frequency with which the audio signal surpasses approxi-
mately 60kHz of deviation. The indicator is based on music signals, not test
tones.
Again pressing the setup button will get us to the balance setting. The balance
simply attenuates one side or the other depending on the adjustment. Set in
the center there is no attenuation. Use the [UP]/[DOWN] buttons to swing the
balance to the left or the right. The best way to adjust this is to listen on a re-
ceiver with headphones, and then adjust the balance until lead vocals sound
like they are in the center of your eyeballs.
The last setup display is the power setting. This is a relative display simply
showing you the drive through the level adjustment pin diode. However the
power adjustment is not incremental like the display. For example, ½ of the
bar is not necessarily ½ of the power. If you want exact power settings you’ll
need to use a piece of test equipment such as our sensitive PM50 to adjust it,
but that is not strictly necessary. The best thing to do is to set up your unit and
antenna as you intend to use it normally. Then, using a portable radio, go to
the furthest distance you intend to receive the transmission from the FM30
Содержание FM30
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