Eddy -
Yes, you can change the sidetone frequency that way. However, (there's
always a 'however',) the sidetone frequency is set to approximately the
same frequency as the CO is offset for CW. This is so if you set the
incoming CW signal for approximately the same tone as the sidetone, your
transmitter will be close to the other station's frequency. The
frequency is typically around 800-900 Hz, and a secondary problem is
that it is more 'sawtooth' than 'sinusoidal'. There are a couple of
assumptions in this scheme that no longer necessarily hold true, but
that's another 'however'.
This tone is ALSO used in the TUNE mode, the electronic equivalent of
'whistling into the microphone', to produce a single tone SSB signal to
tune up with. The lower edge of the filters in the T-4X is not as steep
as the later models, so moving down to 450 - 500 Hz _probably_ would
be ok. But obviously the tone generated must be within the passband of
the LSB crystal filter.
The resistors and capacitors are selected to produce a 90 degree phase
shift at the desired frequency to set the tone that is generated. All
Rs and Cs must be the same value. Someone made up a chart of the values
for each frequency, I'll see if I can find it. When you look at where
those components are located, you might be more interested in the
following suggestions. :-)
I just set the receiver to ON, so that it stays on all the time, so I
can hear my OWN signal. The AVC does a terrific job of minimizing the
loudness, which I help by just pushing the phones forward rather than
right over the ears. This works great, I know exactly where my
transmitter is with regard to the other signals, and am listening to a
nice clean audio tone.
The other 'recommended' fix is to just use a keyer with it's own
sidetone, and put the receiver in STANDBY. You can either turn the
SIDETONE control all the way down, or just don't connect the cable, as
long as you don't need VOX!
Another way would be to use the ~-60VDC level on the key in the UP
position to turn off an external audio oscillator that comes on when the
key is DOWN.
If you use a straight key or bug, then do what we used to do and just
listen to the transformer hum!! :-)
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-B, C-Line&
TR-4/C Service Supplement CDs
<www.k4oah.com>
Edward Swynar wrote:
*/Hi Guys,/*
My poor old tinitus-rattled ears find the internal CW sidetone
oscillator frequency of the T-4X to be very fatiguing after
awhile...it's /too high/ in pitch for my liking in extended operating
sessions...
Has anyone ever /lowered/ the sidetone monitor frequency in their
T-4X...? Would any such change simply entail increased values of one
(or all) of the resistors R70, R71, & R72 (330K ohms stock each), as
well as increased capacitances for one (or all) of the
capacitors C129, C130, & C131 (180-pfd. stock each), at sidetone
oscillator V9a (12AX7A)...?
Many thanks for any & all feedback in this regard...
*/~73~ de Eddy VE3CUI - VE3XZ/*
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