Dentron MLA-2500 manual

Dentron MLA-2500 manual
The MLA-2500 is a good quality SSB linear amplifier with 600 watts total plate dissipation
and a 1KW DC CCS input rating, covering the traditional ham bands from 160 to 10
meters plus a bit extra for MARS.
The output band-change circuit is a PI-network that switches extra capacitance into the
plate side of the circuit on the 160M and 80M bands as well as doing the same on the load
side for 160M, 80M, and 40M. This allows a compact tuning capacitor design which still
maintains generous spacing between the capacitor plates, at the expense of expanded
frequency coverage on some bandswitch positions.
The power supply is a full wave voltage doubler producing about 2400VDC (no load) with
a total filter bank capacitance of 25uF.
The MLA-2500 will produce an input power of 2KW PEP ("full legal power" -as defined
under the old rules). This interpretation obviously means SSB only, as averaging the 1KW
DC (old rules) power input for SSB has been generally taken to mean 2KW PEP input.
CCS DC input for CW, data, and SSTV is to be limited in the real world to 1KW, due to
power supply limitations and cooling arrangements. Since the amplifier was designed to be
compatible with the old rules which measured "power" by averaging DC input to the final
amplifier rather than by measuring peak output power, this amplifier should be considered
to be capable of about 1200W PEP output on uncompressed-voice SSB and about 650
watts output on CW and data without exceeding the component ratings.
Eimac data gives the pair of 8875 triodes an output rating of 1174 watts (CCS).
No rating is given by Dentron for AM operation of this equipment. AM operation is hard on
both the power supply and tubes of SSB-type amplifiers. Our reccomendation for AM is to
run no more than 180W carrier output, or 950 watts DC input. Power supply ripple will be
about 2.6% under AM carrier conditions.