[AMPS] Dentron MLA2500B

[Joe Subich, W8IK]

At 10:54 AM 12/3/97 EST, KM1H wrote:
>
>
>The amp will do 1800W but for tube longevity keep it in the 1200-1300W
>range. Make sure that the grid swamping resistor, R-1, is in the circuit.
>Many MLA owners cut it out to get even more power!
>

Max ratings for the 8875 are 2200 volts at 350 mA or aproximately 1500 
watts input.  However, the Eimac catalog (4/92) I have lists operation 
at 2000 volts and 500 mA peak (per tube) with a resulting 587 watts of 
"usable output" per tube.  The tube is rated for 300 watts plate 
dissipation ... so I wouldn't push them.  

R1 was a 100 ohm wirewound resistor ... with it in place, the input 
impedence of the MLA-2500 is about 30 Ohms with 40 pF shunt capacitance, 
making the amplifier difficult to drive with solid state transmitters. 
The amplifier requires a non-inductive swamping resistor of aproximately 
50 Ohms/25 watts (to suck up about half of the drive from they typical 
200 watt rig) and a 2:1 un-un (to bring the drive impedence back into 
the 50 Ohm range).  Even then, the shunt capacitance (tune input) can 
make the exciter/amplifier system unstable on some bands depending on 
coax lengths. 



73, 

   ... Joe Subich, W8IK  ex-AD8I
       <w8ik@ibm.net>

"Hindsight is an exact science."


--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm