[RTTY] RTTY Capable Amp

[Phil Duff]

At 13:29 12/30/2003, Scott Nichols wrote:

>Are there other amps/tubes that better fit RTTY contesting ? I don't need 
>a kilowatt, just 500-800 watts is plenty...

RTTY contesting is a very high duty-cycle mode, especially if you do any 
"CQ'ing".

Choice of an amp with tube(s) that have adequate plate dissipation, a good 
power supply, and good cooling of the tube(s) and power supply is important.

One critical thing that many times is overlooked for RTTY duty is the 
construction of the amp power supply including the ratings of the power 
supply and plate transformer.  An amplifier's power supply is the heart of 
the beast.  The larger the transformer KVA the better and an amp power 
supply & transformer should be compared using CCA continuous key down 
ratings instead of ICAS if possible, especially for RTTY duty.

I've been using an ETO/Alpha Power 91b for 7 years including RTTY 
contesting with no problems. I usually run it at about 1kw output where it 
loafs.  The 91b/99 series use a pair of the Svetlana 4CX800 ceramic 
tetrodes for a combined plate dissipation of 1600W and a tube replacement 
cost of peanuts compared to ceramic metal triodes such as the 3CX800 or 
3CX1200, etc.  The 91b's power supply transformer is rated at 3+ KVA and 
use of the optional power supply cooling fan is recommended for high duty 
cycle modes.

73 Phil NA4M


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Phil Duff  NA4M   Ann Duff  Georgetown, Texas