In my last post I had asked members a few questions about the Century 22
circuit. And had intended to provide a link to the circuit diagram, but
did not!
Here it is, and the RCVR/CONTROL board that I was asking about is on pdf
page 17 in case anyone might want to have a look:
http://www.tentec.com/wp-content/uploads/2016/05/Century_22_Manual84ce.pdf
Here is my post again, from several days ago:
Hello All,
I got out my Ham Morse app which allows changing the tone to a specific
frequency and tried various tones until I got a close match to the Century
22 peak signal with the filter dialed all the way out. That is, no AF
active filter engaged.
It turns out to be around 725 Hz, quite close to the spec of 750. To my
ears it does have a bit of width but that little band tunes fairly
sharply.
I tried this with both the speaker and the stereo phones that I use.
725 is a bit high for me, so I am wondering if anyone knows of any
frequency shaping components in the audio chain other than the AF active
filter. I will puzzle over the circuit diagram a bit more to see if I can
pick out some likely candidates to experiment with. I'm thinking that
maybe something like 625-650 would be nice unless there is some reason not
to take the radio there.
The manual does not mention an AGC for the rig. Does anyone know if there
is any AGC?
I see a BJT right after the mixer filter along the balanced detector"s
output (on the RCVR/CONTROL board). Its base connects to the S-meter
circuitry. I also see a BJT connected just before the input to the AF
power amp.
Both the S-meter circuit and the BJT next to the power amp have arrows with
a "T" indication. I am thinking that the "T" indicates the transmit
function. But, I see a "T" indication coming off that board on the chassis
wiring diagram for three different multi-contact connectors and each "T"
going to a different board! Does anyone know if those two BJTs are
involved in muting or AGC?
TU,
Garry WA1GWH
near Syracuse, NY
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