6 years ago, I modified my SB220 with a new input Pi network(raised
Q), with some AG6K parasitic suppressor mods, with various other
improvements including step start, better RF relay switching, better
HV diodes, capacitor equilizer resistors, etc. Here are the test
results for the amplifier when driven by IC735 and a key. I think i
was using a Bird 43 with Peak hold modification board. Used Bird
oil-cooled dummy load.
The results show the improvement had on input match, esp to 40 and 10
meters. Some other bands were marginally better. Gain was better in
most cases, got more grid drive into 3-500Zs. The second test shows
the power ouput, with this unit wired for 240VAC. I am not sure if my
unit is typical, and in retrospect I thought the plate voltage Ep
should be higher in SSB. Perhaps I made an error in the records, that
was 5 years ago, and i just typed it all into Excel for the first
time. The triodes are many years old in this rig, but I am not
complaining about the RF power it makes. Note that at 10 meters it
definitely slumps off. The 'apparent' calculated plate dissipation
went up to, but I suspect the tank circuit and nichrome are some of
the dissipators of the missing RF output power.
If anyone wants to see circuit diagram of the SB220 with finished
mods, let me know and I can email a GIF file
directly.
73
John
K5PRO
Input Match Tests:
50 Ohm Load, Fast Dits, CW mode
Heath Stock Input Network 2/13/94
Modified Input Network 2/20/94
Freq (MHz) Pout Ig(mA) Ip(A) Input VSWR Pout Ig(mA)
Ip(A) Input VSWR
3.51 450 80 0.36 1.1
485 120 0.45 1.5
3.6 500 80 0.36 1.1
540 120 0.41 1.4
3.7 550 85 0.35 1.1
580 135 0.41 1.2
3.8 600 85 0.34 1
640 140 0.4 1.1
3.9 650 90 0.34 1
650 155 0.4 1
4 650 85 0.34 1.1
610 145 0.41 1
7.01 750 100 0.39 3
670 165 0.41 1.4
7.1 950 125 0.47 3.1
680 150 0.4 1.2
7.2 750 100 0.4 2
680 155 0.4 1.1
7.3 700 90 0.38 1.5
670 160 0.395 1
14.01 670 90 0.35 1.1 680
165 0.42 1
14.1 680 110 0.33 1.1 670
160 0.44 1
14.2 670 105 0.33 1 670
165 0.43 1
14.3 690 100 0.34 1.1 680
170 0.43 1
14.35 680 90 0.34 1.1 680
170 0.425 1
18.14 no good
no good 2.8on 15 MB setting
21.01 650 130 0.34 1.2 670
160 0.45 1
21.1 600 80 0.31 1.15 670
165 0.44 1
21.2 550 90 0.3 1.2
670 165 0.44 1
21.3 650 95 0.34 1.15 680
165 0.44 1.1
21.4 650 95 0.33 1.1 670
170 0.44 1.1
24.94 550 115 0.33 2.1 no
good 3.5on 15 MB setting
28.01 420 85 0.33 3 470
155 0.39 1.2
28.1 350 80 0.32 3
480 150 0.395 1.2
28.2 350 70 0.3 2.8
480 140 0.4 1.2
28.3 350 80 0.32 2.4 480
135 0.4 1.15
28.4 500 90 0.34 2
480 135 0.4 1.2
28.5 600 175 0.36 2 480
135 0.39 1.2
28.6 600 120 0.38 2 480
138 0.39 1.15
28.7 650 140 0.39 2.1 480
138 0.39 1.15
28.8 650 160 0.39 2.5 480
140 0.39 1.15
29 680 130 0.4 3
470 145 0.375 1.3
29.2
470 130 0.38 1.3
29.5 500 80 0.32 3
470 135 0.37 1.4
29.7
460 130 0.37 1.4
RF Power Tests:
50 Ohm Load, Fast Dits and keyed down, SSB mode
2/20/94
Freq (MHz) Pout Ig Ip Ep DC Pin
Loading n1% n2% Plate Dissp (W per tube)
3.88 1080 240 0.64 2300 95
4.5 69 73.3 243
7.2 1150 230 0.68 2300 90
4.4 69.5 73.5 252
14.25 1200 265 0.71 2300 85
4.4 69.8 73.5 259
21.3 1250 265 0.71 2320 85
4.9 72 75.8 241
28.35 920 210 0.62 2380 85
5.2 59 62.4 320
NOTES:
n1%= Pout/[(EpxIp)+Pin] Power-added efficiency
n2%= Pout/(EpxIp) Output efficiency only
Plate Dissp=(Pdc + Pin) - Pout (some lost in grid and ciruit also)
10 meter losses are higher in Nichrome parasitic suppressor
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