[R-390] audio deck saga *more*

[Flowertime01 at wmconnect.com]

W Li,

Not a problem.

You changed some parts so you changed the gain of the stages. At least at 
the 400 hertz band pass. You think it sounds better so this is good. Opening 
up the band width for better fidelity looks as if you did not hurt the 
signal to noise of the stages.

As you open up the band pass you get more noise through the pass for the 
same narrow signal in the pass.

It may measure real good on the instruments. The change is all in the audio 
after the detector stages. So it will not change the receivers ability to 
discriminate between signals. A 2Khz IF filter is still trimming the input. 
The detector is still giving you the same audio envelope of the signals. You 
just get more audio fidelity because you opened up the audio band pass 
(those caps changes) and you get more gain (because you changed some resistors to 
change some stage gains). So I do not think you will get a lot more noise 
when working real signals.

As today, there was lots of bad thinking going around and people in charge 
made poor choices or at least choices we would not have elected. I think you 
found some changes that will let these receivers sound better.

Now as you put RF into the antenna input you expect to get better than 20:1.

On a stock receiver we put 455 into the IF and expect 30:1 and put RF into 
the antenna and expect 20:1.

I do not know if your 47:1 at the IF will yield 37:1 at the RF. But I think 
you could expect something better than just 20:1.

A nice hot 30:1 would let us pull some more CW out of the air.

I bet AM radio sounds much better.

Do you think SSB is better the same or poorer after your changes?

If you think the audio is sounding better then the change is worth the 
effort.

Could you give us a list of part number, old value, new values for your 
changes.

Good Job on all the work and bringing it in on a project you like the end 
results of.

Roger Ruszkowski AI4NI