If it is not up to 375 watts on AM then how does one justify the RTTY an
SSTV limit of 650 watt limit, 50% duty cycle, 10 minute transmission limit?
After all RTTY and SSTV is a carrier mode with 100% duty cycle.
PEP power is PEP power be it SSB or modulated carrier. There's no
difference except for duty cycle.
As to your 160M operation, I suggest you look at your tuning very carefully.
My Centurion is a 1991 vintage, original tubes and the Bird 43P indicates
1200 watts plus with an Ip of about 700 ma and Ig of about 120 ma on 160M -
20M. The tubes show very little color except when in a tune condition with
100% steady state carrier at the 1200 watt output level. Then they warm up
nicely. According to recent discussions, this is the opportunity for the
"getter" to de-gas the tubes. Perhaps you are too gentle on yours and the
tubes have "gassed up". The 15M and 10 M bands aren't quite as efficient.
When driven with the Collins S-Line, which has a bit more output than the
Omni VI Plus, on 20 M the Bird 43P shows slightly more than 1500 watts.
Here Ip is 800 ma and Ig is 130 ma. I might add that the amp does have a
bit more gain on 20 M than any of the other bands. Plus I have a real solid
235 VAC line to the amp.
My experience is that there is NO PROBLEM running the amp at the 300 watt
carrier output level on AM as long as the Tx time does not exceed the Rx
time {i.e. 50% duty cycle}, with a max Tx time of 10 min. By that time one
needs to ID anyway and let the other 5 fellows in the round table take it.
By the time is gets back, it has had some 50 minutes of rest.
73
Bob, K4TAX
----- Original Message -----
From: "Rob Atkinson K5UJ" <k5uj@hotmail.com>
To: <tentec@contesting.com>
Sent: Tuesday, December 13, 2005 11:35 AM
Subject: [TenTec] Jupiter selectivity
<<<This power level is just about correct for driving a
Centurion to legal AM limit of 375 watts carrier.>>>
I'd never drive a centurion to 375 w. cxr on AM. It is simply not up to
that kind of duty. It lacks the cooling and power supply robustness for
that, and can barely handle an AM transmission of even just a few minutes
at
200 w. cxr. Do a geezer transmission and you'll melt it down. at the
least, the fan should be changed to something that moves 3 or 4 times the
volume of air over the stock quiet fan volume before AM is attempted at
200
to 300 w., as the Centurion was intended to be a quiet desktop ham cw/ssb
amp. For rtty ten tec wants you to run no more than 600 or maybe it's 800
w. and not for very long. the combination of a carrier and two sidebands
is asking a lot of this amp. perhaps i am overly cautious. if i run mine
at 1 kw pep on 160 LSB for a 5 to 10 minute transmission the plates get
bright orange and for that 1 kw i am darn near the 800 ma max for Ip.
forget 1.2 kw on that band.
73,
rob / k5uj
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