|[AMRadio] coupling cap on the moduation transformer secondary|
w5omr at satx.rr.com
Tue Aug 16 22:38:02 EDT 2005
Donald Chester wrote:
>You don't need 10 Hz low end response, thats wasted power since most
>reproduce that. Also, the capacitor is just another source of stored
energy in your radio, to deal
>with from a safety standpoint. More is not always better.
But to avoid excessive phase shift distortion, the uniform frequency
response should extend at least one octave above and one octave below
the intended range of frequencies of the modulation.
Therefore if, for example, your target is to actually transmit audio
ranging from 100~ to 5000~, the speech amplifier/modulator should be
essentially flat from 50 to 10,000~. Even "communications quality
audio" response of 300~ to 3000 would require at minimum a uniform
response in the audio section of the transmitter of 150~ to 6000~.
UTC ran this recommendation in their LS- series transformer catalogue,
and I seem to recall seeing it in Thordarson's Tru-Fidelity catalogue also.
yeah, I'm thinking the same thing. So, if I don't have enough C in the
output of the power supply, I could always add another, which would make
them in parallel, which would ADD to the total capacitance in the power
supply, and whatever coupling capacitance was used would effectivly be
(as I understand it) in series with that power supply output capacitance.
Which means if there's 10uF in the supply, and 10uF to be used as
coupling, then a total of 5uF would be seen, as far as coupling is
concerned and if BC stations are using 1 and 2uF and you're using 4uF,
Don, then I should be in no danger of hurting anything here. ;-)
Neat discussion - I like it.
73 = Best Regards,
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