VHF Power Amps

YD1270 23cm Power Amplifier

Published in Radioamater magazine in Serbian

Important notes:

All connections between RF parts, and also connections to ground MUST BE as short as possible! This is VHF, not HF, in spite that designs may looks like HF! Hi! See mechanical layout of PA designs below!

If input circuit trimmers, need to be at maximum or minimum capacity during adjusting, it is necessary to change the length of the cable between the exciter and the amplifier itself. The optimal length of the cable should be determined experimentally to obtain adjustment with approximately the calculated values of capacitances. This experimentally determined cable should always be used when operating the amplifier. A change of exciter could occasionally require a new length of cable to be determined.

Power amplifiers for 144 MHz /zip 2790 kB/ (1988.)

(TXT in Serbian)

for tubes: 4CX250B, 4CX300A, 2C39BA i TH328.

1-1 1-2 1-3 2-1 2-2 2-3 3-1 3-2 3-3 3-4 3-5 4-1 4-2 4-3 4-4

TH328 2m PA built by Boris, S51MQ

TH328 2m PA - built by Popa, YU7EF

3x2C39BA 2m PA - built by Vlada, 9A4VM

Tetrode power supply

Power amplifiers for 432 MHz /zip 1355 kB/ (1990.)

(TXT in Serbian)

for tubes: 4CX250B, 4CX300A, 2C39BA i TH328.

1-1 1-2 1-3 1-4 2-1 2-2 2-3 2-4

2m PA built by Teo, YU7AR

2xBLX15 6m PA built by Saša, YU1EO

6m PA built by Mark, VK2MJS

VMOS Solid State 2m Power Amplifier

2xDV28120T Push-Pull

Pages from RSGB VHF-UHF Handbook Ch4.pdf

Built by Aca, YZ1SAN

Balun Modification

Instead of wideband baluns made of 95 mm long coax cable wound onto ferrite torus or large ferrite beads, it is possible to build 144 MHz resonant balun made of 620 mm long, 5mm diameter PTFE coax cable RG142 or similar, wound 6 turns as usual air coil, with 30 mm inner diameter and about 30mm long. No space between turns. For 50 MHz balun, coax cable length is 1770 mm, coil inner diameter is 50 mm, coil length is around 55 mm and turns number is 11.

New! Not yet published in magazines

MOS Solid State 70 MHz Power Amplifiers

1 x BLF147

PCB: 120x64 mm

Measured by S59MA:

Uds -- Ids -- DC Input -- Pdrive -- Pout -- Eff % -- Gain --Disip.
27.6V -- 8.65A -- 238W -- 3.63W -- 148W -- 62% -- 16.1dB -- 90W
13.8V -- 4.60A -- 63.5W -- 3.63W -- 36.3W -- 57% -- 10dB -- 27.2W

Built by Ales, S59MA

2 x BLF147 Push-Pull

New! Not yet published in magazines

Published Articles

in magazines

3x4CX250B 2m Power Amplifier

YL1056 2m EME Super Power Amplifier

3x2C39BA 70cm Power Amplifier

YD1270 23cm Power Amplifier

Published in Info Elektronika, CQ ZRS and Radio T9 magazines

Balun Modification

Balun Modification

New! Not yet published in magazines