ANTENTOP- 01- 2008, # 010

2xGU50 and 3xGU50 PA from UA1TAT

2xGU50 PA

The PA was designed and then made (in several samples) by Yaroslav Zhukov, UA1TAT. It is a "classical" Tubes PA with grounded first grid. However, the feature of the PA is the individual bias for the first grid of each of the used tubes. It allows use tubes with slight different anode/grid characteristics.

Yaroslav Zhukov, UA1TAT

Credit Line: http://hamnv.narod.ru/2gu50.htm

Credit Line: http://hamnv.narod.ru/3gu50.htm

Figure 1 shows the schematic. Third grid of both tubes is grounded. Second grids of the both tubes are connected to 250-V voltage stabilizer.

The PA was designed for CB-station for 27-MHz. It

is defined the input circuit that provides good matching at the band.

3xGU50 PA

The PA is made on the base of 2xGU50 PA. Output power of the 3xGU50 PA is 180- 200 Wtts. The PA was designed for 160, 80, 40 and 20 meters. Input circuit is broadband and can match the PA in wide frequencies range. The input circuit is described at Antentop- 1-2008, p.62. Figure 2 shows the schematic of the 3xGU50 PA

At practical design it was found that capacity of the high-voltage capacitor at matching circuit is changed a little inside the working band. It allows to me to change the hard-to- find capacitor for available for me constant capacitors. The capacitors are switched with help of a usual ceramic switch.

P.S. My thanks to Sergey Mironov for the help during design, manufacturing and tuning of the PA.

GU81M- Made in the USSR

http://hamnv.narod.ru

http://www.antentop.org/

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