[TenTec] Century 22

[Garry Nichols]

I've been approved at the Ten-Tec groups.io discussion but it looks like
some folks are still at this discussion site.  No one replied to the post
Gary made for me before my approval, so I will repost here to see if I get
any replies.  TU,  Garry  WA1GWH


I picked up a C-22 in July, S/N 666.  Does anyone know how many were
produced? I am wondering where mine sits in the production run and what
might have been changed along the way.

I've heard that some of these rigs had capacitors in the AF filter that
lowered it to 500 Hz center frequency and that C41-C48 (.0033) should be
replaced with .0022.  Have not examined that on the board yet but wondering
if by #666 this had been corrected.   And if those cap numbers and values
are correct.

The variable bandwidth AF filter is very effective but I do not like the
way it sounds.  It is always set for minimum bandwidth and the adjustment
pot just bleeds varying amounts of unfiltered AF into the output stream to
the LM380 to widen the bandwidth.

Because it is set for minimum bandwidth (200 Hz in TT specs) it has a
pronounced "sea shell" effect on the audio.  This is apparent even when
blending in large amounts of unfiltered AF.

Is there any mod to widen the bandwidth?  Looks like I can drop off a stage
or two of filtering to widen it as was done with the C-21 switch selected
bandwidths.  I have pretty good mental selectivity.

I would also like to lower the center frequency somewhat below the 750 Hz
design.  Is there a mod for this?  (I've apparently answered my own
question, above.  But with the filter dialed out the rig still seems to
have a peak around 750 Hz to my ear.  Perhaps there is some filtering
before and/or after the AF filter?)

My radio has the built in Ten-Tec keyer but I get unsure code with my
iambic paddles (which I simply push side to side, no squeeze keying).  I'm
thinking the keyer might need a single paddle key to work correctly?  I may
be confusing it with a dot or dash inserted reflexively before I let go
completely of the other paddle.

The drivers and the finals are not the same as are shown in the Ten-Tec
manual circuit diagram.  The circuit shows an MRF476 for a driver and my
radio has an MRF472.  I think there is something coded before the MRF472
but it cannot be made out.  There is something after the MRF472 and a space
but its initial coding cannot be made out.  I can see that it does end in
"12".

The finals are shown as MRF475 on the circuit diagram but my radio has
25073 then a space and an M with the rest obscured but the field ends in
824.

I have heard that there were changes and substitutes for the drivers and
finals along the way.  Can anyone give me any info on my situation,
please?

The rig's signal seems fine.  I have only taken it to 10W so far out of
caution.

And the last point:  The QSK sounds a bit "sparky/poppy" at times.  Is this
the way these rigs are supposed to sound?  My SW-40+ and 4SQRP Cyclone 40
also have these sounds to some extent.

Thank you for any comments that might be made.