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Old March 11th 05, 01:49 PM
 
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hey, thanks for the info. that was very helpful! as you probably
expected, i would like to ask a couple of follow-ups on 2 of the
questions:

xpyttl wrote:

2. other than frequency range, what characteristics are you

concerned
about when trying to match a transmitter to an amp?


If you are buying commercial, you are looking at price, of course,

and
expected reliability, along with power consumption. For SSB, you

need the
amplifier to be linear, which implies lower efficiency. For FM/CW

you don't
need linear, so the amp can be a lot more efficient. If you are

designing
the amp, then you are worrying about impedance mathcing, as well.


i guess what i meant was more along these lines: you need to make sure
the peak-to-peak input voltage and current capabilities of the input is
matched with the amp, right? or does the amp have a lot of leeway in
those regards?

4. for an FM transmitter, does the modulation occur to oscillator
directly, or is the oscillator's signal modulated after "leaving"

the
oscillator? i guess what i'm asking is whether or not there is an

input
to the oscillator, or is it just an "output only" frequency

generator?

Typically you would modulate the oscillator, although these days, the

audio
may well be simply data to the synthesizer. However, because FM is
typically done at VHF and higher, there may well be additional

oscillators
mixed with the modulated signal to get up into the VHF/UHF range.


just to make sure i have it straight, if i were to transmit a sine wave
at 146mhz, anyone listening in on 146 mhz wouldn't hear anything
(except maybe less noise than usual). if i were to vary the frequency
between 146.0001 and 145.9999 at a rate of 100hz, then anyone recieving
would hear a quiet 100hz tone. now if i were to vary the frequency
between 146.001 and 145.999 (holding all previous listeners constant),
then anyone listening would hear a much louder tone...correct? or am i
not understanding it yet? ;-)

thanks again for the help!
jason