Alpha 91B
Home Up Alpha 86 Amplifier Alpha 91B Ameritron ALS 500M Solid State AMP Henry 4K Henry 2002A Henry 2006A Ten Tec Titan

 

Alpha 91B 1.5 KW  Amp

 

Alpha 91b front panel.  No grid current meter - only Min and Max.
Power supply and transformer section
RF section and two 4cx800 tubes.  Upper left part in black is fan motor pushing air up through tubes and out top of cabinet.
Back with RF in/out, ALC, Relay in and Relay out.  Also 2 twenty amp fuse holders.

 

Operational Commentary:

This amplifier is a joy to use - especially with 100 watt exciters.  I use this amp with my 756PRO and 775.  The feature I like is the less than 50 watt drive for full output.  The two 4CX800's take as little as 35 watts up to about 60 watts (per Icom watt meter in radio).  This is great in RTTY when I run up to 90% duty cycle.  Exciters run nice and cool.  Bandswitching takes about 15 seconds as I have a band table taped to the upper left corner of the amp.  Output is 1500 watts on all bands including WARC.  This amp is a 1996 model determined by the serial number.  Very nice a quieter than my Alpha 86's, but they also have the external fan and this 91b doesn't (never needed it).  A nice amp - a little lighter in weight and power than the Alpha 86's but nice anyway.  I run the amp off the Icom Relay/Send 1/4 phono plug (on the back panel of the Icom) direct to the amp - no fancy interfaces needed!  ALC not used, but I do monitor RF output with the Kenwood 220 monitor.

Setting and Power In verses Power Out

Control Setting And Power Reading for Alpha 91b s/n 961610297

BAND

FREQUENCY

TUNE

LOAD

PIN

POUT

NOTES

160

1.90

48

70

40

1500

160

2.00

20

38

35

1500

80

3.55

90

68

30

1500

80

3.75

76

76

33

1500

80

3.95

60

62

30

1500

40

7.02

60

40

40

1500

40

7.20

59

45

38

1400

30

10.12

78

74

42

1500

band "40"

20

14.20

44

68

50

1500

17

18.10

72

64

50

1400

band "15"

15

21.25

18

70

40

1400

12

24.90

90

74

50

1400

band "10"

10

28.10

26

74

45

1500

10

28.50

26

76

40

1500

10

29.00

18

76

40

1500

10

29.60

10

80

40

1500

Notes:

TUNE is tune control settings

LOAD is load setting

PIN is power input as measured on Icom 775 internal wattmeter

POUT is power measured on Bird 43 wattmeter with 2500H slug

Antenna was Heathkit Dummy Load (Cantenna)

Measurements on 5/25/01 by Bob Brehm, AK6R

PIN was increased up to 1,500 watts POUT or until MAX grid LED came on.

These settings are unique to this amplifier and your settings may differ