Bob -
The 'normal' audio passband for the transmitter is 325 - 2725 Hz. The RTTY jack shifts this to ~
825 - 3225 Hz to pass the 2975 Hz tone of 850 shift. It ALSO moves the carrier further down the
skirt of the LSB filter, which would improve the carrier suppression by ~ 10 dB. I will say that I
never had a problem with carrier suppression, but additional suppression certainly wouldn't hurt.
So unless you have some other reason for NOT using it, I'd say continue. There is no downside that
I can see.
I love to get a copy of that RTTY sheet for my CD. I have one for the A line, but nothing for the
C-Line.!
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Robert Ladden wrote:
The Drake bulletin for RTTY recommended using the carrier shift even when using
narrow shift RTTY:
"Even when using narrow shift, this shift circuit provides additional carrier and opposite
sideband rejection."
I've been using it. Should I not bother?
73,
Bob WW3QB
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*
*
Bob -
The C-Line does fine for RTTY. The transmitter has a jack on the back panel marked RTTY that when
shorted shifts the carrier a bit to ensure that both tones (2125 - 2975 Hz 850 Hz shift,)were
passed through the LSB filter unattenuated. It was originally designed when we were still using
850 shift, but is no longer of any value for today's (2125 - 2295 Hz 170 Hz shift) and should be
left open.
I ran multiple 4 Series transmitters on RTTY for some years, at full power and with transmissions
of 30 minutes or more. You have to run them just UNDER the ALC threshold (just below where the
output levels off) as you increase GAIN. PA tubes lasted a couple of years that way, with 'end of
life' at 100W output max on 14.075 MHz. Obviously a small fan is a BIG help, either on top
(blowing UP) or on the rear panel of the PA cage (blowing OUT).
For contest type transmissions (excepting 10 minute CQs!) I wouldn't hesitate to use full power,
about 340 mA. If you make long CQs, I'd back it down to about 300 mA. (~ 100W output) and the PA
tubes will last 'forever'.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com <http://www.k4oah.com>>
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