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HF 15Kw Power Amplifier using 4CX10000D | Radioaficion Ham Radio

HF 15Kw Power Amplifier using 4CX10000D


15Kw HF Power Amplifier using 4CX10000DDC9DZ: Project Tsunami – 15Kw HF Power Amplifier using 4CX10000D

Project Tsunami or 3 years of work due to a bet about a crate of Bitburger beer

Burkhard, DF5XV,, owns a Monster-PA of R&S called VK20. The live weight of this PA amounts to 1.6 metric tons, it needs a big room on its own with a defined supply and exhaust air and its output reaches frightening 20 Kilowatts, even for RTTY. As a driving transmitter a R&S SK01 is required. Burkhard has an official permission of the BNA for 20 KW on shortwave for broadcast, although not for ham radio. Such enormous values of transmitting power challenge even the creativity of an experienced high frequency engineer. Well, three years ago, the author of this article placed a bet against Burkhard to build a power amplified with more than half the output power of the VK20 in SSB mode, yet would fit the trunk of a compact car as well as a manageable weight. Burkhard's answer: No way! So the race was on!

After three years have passed, the project with working title “Tsunami” is finally completed. Even the additional difficulty of a minimal required input power of only 100 Watts, achieved by every amateur transceiver, in order to attain the full SSB transmit power of approximately 15 Kilowatts was accomplished. A total amplification of about 21 dB is technically very ambitious as it was not the goal to build a power oscillator.

The tube which satisfies the technical requirements of the project “Tsunami” for sure without reaching its limits is the 4CX10000D. According to the Eimac spec sheet for SSB linear


Data of Tsunami RF Linear Amplifier

RF linear amplifier covers all amateur bands from 1.8 MHz to 29.7 MHz

3 Power supply transformers
Plate voltage at full output power
Screen voltage, stabilized
Grid voltage, regulated

10000 VA , 1200 VA & 1 VA
6500 V
1000 V
- 245 V +/- 20 V
7.5 V / 75 A

Input SWR in the middle of band

160 m – 30 m
20 m
15 m
12 m – 10 m

1 : 1.25
1 : 1.35
1 : 1.45
1 : 1.65

Gain (1.8 – 29.7 MHz)
Neutralization 1.8 – 29.7 MHz:
Isolation between input and output

20 – 21.6 dB

45 – 50 dB

Output with:

5 W Input:
10 W Input:
20 W Input:
30 W Input:
40 W Input:
50 W Input:
60 W Input:
70 W Input:
80 W Input:
90 W Input:
100 W Input:

0.75 KW
1.5 KW
2.9 KW
4.4 KW
5.8 KW
7.3 KW
8.7 KW
10.1 KW
11.6 KW
13.1 KW
14.6 KW

Input: SSB Signal:
33% of full 1 KHz Modulation
on / off Ratio 1:2, Interruptions: 20 Hz

R&S 20 KW Dummy Load
Bird Power Meter

on 7.1 MHz


Harmonic output
Intermodulation distortion

50 dB below rated output
35 dB or better
Eimac 4CX10000D

Input network:
1:9 Transformation, 450 Ohm, 500 W HF Resistor, Tube Input Reactance Compensation & Neutralization for each band, 11 pol. bandswitch, two levels
Output network:
Roller inductor 20 uH & 2 motorized vacuum capacitors 500 pF / 15 KV and 2.5 nF / 5 KV
Metering: Display of all parameters – no switching
Computer control of all switching functions: No relays switching under power conditions
Soft start inrush, 10 sec delay time for full power
Turbine blower with 2 speeds
Well regulated screen and grid supply for +ve and -ve currents as well as current limiting to protect the tube and minimize the IMD. It's impossible to override the screen and grid dissipation at any working conditions
The finish is of high quality black eloxial aluminia

Accessory (for Icom-Transceivers)

575w x 310h x 585d mm
132 Kg
Module for optimized tuning (1 KHz; on / off: 1:2, 20 Hz)
Very low: About 1.7 €/W (1.7 €/W x 14.6 KW = 24.8 K€)

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