I said "not loud enough" because the PIN diode bridge takes a higher control voltage to give less attenuation,
backwards from the FET attenuator we usually see in this forum.
You decide if it is "not loud enough" by comparing the DC from the detected audio against some threshold voltage
with an op amp or similar.? Seems like this would work well enough if you want the audio to always have the
pretty much the same volume at the speaker, though I suppose it would be preferable to have really loud
incoming signals come through a bit louder at the speaker in a well defined manner.
Don's 1n4148 attenuator won't be doing any better in this respect.
Figure 5 of the BAP64Q datasheet shows an input return loss of better than -10dB
across all control voltages of interest when in a 50 ohm environment? ?
So might be good enough for 12mhz.
But you're right, putting near the 45mhz filter would be better.
Jerry
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On Tue, Mar 27, 2018 at 07:45 am, Tim Gorman wrote:
How do you decide if the audio is not loud enough? Especially in a
simple receiver like this? AGC usually works just opposite of this. It
is based on audio being too loud.
