[HCARC] Ameritron AL-811 Three Tube Amp Tests

[galeheise at windstream.net]

To All-

  For those of you that might be interested in this amp, here are the test results from an Excel Spreadsheet:

       Plate Grid Input Output 
       Frequency    Current Current Power Power 
       (MHz)   Load   Plate  (ma) (ma) (watts) (watts) 
           
                1.810        -      0.25  410 150 53 400 
                1.910        -      1.25  375 150 52 400 
                3.550        -      2.75  400 150 56 400 
                3.900        -      4.25  355 142 53 400 
                7.050   2.50    7.50  345 135 50 400 
                7.290   2.75    7.75  330 130 49 400 
              10.010        -      7.00  325 130 60 250 
              14.050   2.60    8.80  355 140 51 400 
              14.340   2.80    8.90  350 140 51 400 
              18.075   2.70    8.60  375 150 61 370 
              18.160   2.10    8.70  350 138 57 370 
              21.050   4.20    9.10  445 150 55 370 
              21.430   3.90    9.30  380 150 40 370 
              28.050   4.25    9.30  375 150 44 250 
              28.400   4.10    9.30  375 150 41 250 


  A couple of important notes:
1.  The 400 watt specification in the manual is for a 1/2 hour continuous carrier so I utilized a CW carrier for the test.
2.  In the Ameritron AL-811H manual the power output values are noted to be at 7 Mhz.
3.  The legal output on the 30 Meter band is 200 watts so I suspect that’s why the value at 10.010 Mhz is only 250 watts.  It may be slightly detuned for the purpose of limiting the output.
4.  The output dropping off on the higher bands is similar to the previous AL-811 that I tested.
5.  All of the drive values are below 62 watts.  To be on the safe side it’s important to have the ALC connected from the transceiver to the amplifier and adjusted to prevent damage from overdriving with a 100 watt rig.

  As with other Ameritron manuals this one has inconsistencies.  For example it says the amplifier was designed to operate at 70 watts of drive.  In addition, point #8 in the Tune-Up procedure says “if the grid current goes over 150 ma reduce the drive at once”.  Yet in point #9 it says “Observe the output on an external RF wattmeter.  Increase the drive until full exciter power (never to exceed 100 watts) or 200 ma of grid current is achieved.  As a result, I played it safe an only ran the input power up such that the grid current was limited to 150 ma.  If 70 watts of drive power is suppose to be typical then when I ran my tests I was consistently operating below the limits.  Pushing the drive up to either hitting 200 ma of grid current or 450 ma of plate current maybe fine, I just didn’t want to push it too hard.

73s
Gale
KM4DR