High Power tube amplifier for 144MHz using the Russian Triode GS35b

Introduction
This page provides information on the design and construction of a 144 MHz high power amplifier using a Russian VHF triode GS35b.
The Russian VHF triode GS35b is specified to operate up to 1000MHz with 1.5KW anode dissipation. Although the tube geometry makes the construction of a compact amplifier difficult, it's possible to realize an EME power amplifier with a good effectivity and medium drive power.
The GS35b has become available at low cost and its specifications are interesting for a 144MHz power amplifier. After searching some time for good and reliable informations, I found the design informations of Thomas (DJ5RE), published in DUBUS 4/1996. DJ5RE's informations are very detailed and easy to follow.

Cavity:
Most of the mechanical setup is taken from the DJ5RE design information. But minor changes to the DJ5RE design informations had to be done. For example, the load assembly was taken from the very detailed informations of DL4MEA and the disc of the coupling capacitor had to be raised to 50mm diameter. For detailed infos, I strongly recommend the description of DL4MEA's GS35b amplifier (144MHz / 432MHz version). In addition I realized a special aluminium tube socket, which is very similar to the socket done by Andy, DL6YEH. You may check my construction details below or Andy's webside for further informations.

Update:
Due to relatively warm air coming out on the top of the cavity, I installed an additionally blower on the top of the cavity, which sucks the warm air out of the cavity. This ensures some cooler temperatures around the tube.

HV power supply and amplifier control:
I integrated the complete HV power supply and the PA control steering into one 4 HE 19" rack. The HV is adjustable in 600V steps from 600V - 3600V and is able to serve 1A continuously. In order to get a perfect control and protection of the amplifier, I integrated the Triode Board of Ian, G3SEK. I strongly recommend this control unit, because it's easy to build and very reliable.


Performance: ...values have been corrected to reality... ;-)


Parameter

Symbol [unit]

Drive Power 50W

Drive Power 35W

Drive Power 25W

Output Power

Pout [W]

1300

1075

850

Gain

G [dB]

14.1

14.8

15.3

Anode Voltage

UA [V]

3200

3250

3250

Cathode Voltage

UC [V]

40

40

40

Bias Current

IA0 [mA]

150

150

150

Anode Current

IA [mA]

700

600

500

Grid Current

IG [mA]

180

110

75

Input Power

Pin [W]

2240

1950

1625

Efficiency

E [%]

58

55

52



You may checkout some design and contruction infos:

  • GS35b Tube Datasheet [PDF]
  • Cavity mechanical schematic [PDF] (Original by DJ5RE)
  • HV supply schematic [PDF]
  • Control Logic schematic [PDF]
  • Tube schematic [PDF] (Original by DJ5RE)
  • Tube socket fixture [PDF]
  • Tube socket template [PDF]
  • Air chimney template [PDF]

Some pictures of my amplifier:

Cavity during testphase HV power supply and amplifier control unit during testphase HV power supply and amplifier control unit in final version top view
HV divider Tube top view Tube bottom view
Complete amplifier placed into the 19 Final rack, front view Final rack, inside view

Finally many thanks for their informations and their support must go to:

  • 144MHz PA with a Triode GS35B , Thomas Hoeppe / DJ5RE, published in DUBUS 4/1996. Many thanks for the permission to publish detailed informations, Thomas!
  • A 144MHz Amplifier with a GS35b, Guenter Koellner / DL4MEA, published on his webside
  • The Triode Board - Control and Protection for your Triode RF Power Amplifier / G3SEK, published on his webside
  • DL6YEH, Andy, for technical support and informations. Check his webside
  • G0HSS, Phil, for technical support and informations
  • DJ9CZ, Karl, (SK) without his big help during planning, production and testing the amplifier would not have been finished!