Alright I'm back, real life intervened for 12 or 15 hours since I asked
the RTTY question.
Thanks for the help guys. The first thing I thought of when I decided to
do this was Garey's stories about running 4 line gear on RTTY 24/7 and
it lasted for years. So I figured I had some margin for error here. My
main concern was not so much wearing out the rig, it was having a sloppy
signal and annoying everyone on the band. I was pretty sure I wanted to
set it right before the ALC started kicking in, but I wasn't sure how to
find that spot. Right before the output curve flattens out, it makes
total sense now, but for some reason it eluded me. Also, I wondered
about the RTTY shift circuit in the T-4XC but forgot to ask about it.
Garey did a nice job of explaining that as well. In fact, I fixed
another T-4XC a few years ago that had a shorted transistor in that
circuit that caused the TX to always be 500HZ, or whatever, low. Garey
pointed me in the right direction on that one also.
I already have a fan on the back of the PA cage, (a Silenex that someone
on the list recommended a while back) it works great. You would be hard
pressed to feel any heat at all with your hand right on top of the
finals after a long transmission (I've tried it, it's amazing). Hey,
come to think of it, is installing a fan on the T-4XC considered a
MOD?........................................just kidding, don't get
started again.
My wife is right, I am a born troublemaker. Well, I'm through here, I
have some cables to make if I am going to do this.
Thanks again for the help,
Bob K6GGO
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>
Robert Fish wrote:
I have been thinking about using my C-line for the RTTY contest this
weekend.
How do I set the transmit audio (gain) level. Do I set it the same as
SSB where
the peaks are about 150ma? I am not set up here for FSK, so its going
to be a sound card affair.
Any general advice for C-line RTTY?
Thanks,
Bob K6GGO
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