Amplifiers

I have built a couple of amplifiers mainly for the VHF-UHF. The largest project was the famous W6PO 8877 amplifier. However I sold that amp many years ago.

K2RIW/W2GN's stripline kw for 2m is an other amp I made that has been working well and still is.

Eimac tubes are good however also expensive. Russian tubes like the GS-31b, GS-35b, GU-74b or GI-7b are much more value for the money. However the GU74 has moved to the west due to ACOM (ACOM-1000) and other amplifiers (Alpha91B) and are not seen cheap anymore.

 

HF GU-74B

This amp is built by an Ukrainian radio amateur (Alex). I have done some "face lift"

Original design.

/oldhfpa.jpg

 

 

Here some face lift done.

Testning the amp on 20M 600W to a dummy load. Also looking at the spectrum which looks clean. 10W of drive about 450mA Ia and 2.3kV Ua. 1kW input which means about 60% efficiency. The meter will also be replaced later.

/img_0592.jpg

Inside.

/insidehfpa.jpg

 

New Meter

I replaced the meter and custom made a new scale.

/newmeter.jpg

 

The scale is made with GALVA, a free software.

 

/oldmeteramp.jpg/newmeteramp.jpg

 

On the Air test.

First I put out 10W and bypass the Amp and look at the spectrum analyzer.

10W to the antenna tuner is equal to -44db on the SA.

100W is -34 db. Make sense, should be 10db gain.

PA on generates -26db. Which also makes sence, 100W to 650W is about 8db. This means that the the power meter on my antenna tuner is accurate compared to the spectrun analyzer.

/spcpa.jpg/mfj.jpg

 

 

2M 8877 

This is how a W6PO design looks like. This one built by 9Q1EK, in mine was all parts silver plated.

/8877.jpg

 

 

 

2M 4CX250b

/4cx.jpg

/img_0480.jpg

 

Input circuit

/img_0482.jpg

 

Top view

/img_0483.jpg

 

 

 

6M TH-430

/th430.jpg

 

 

 

2m-2SC2897

/2sc2897.jpg

 

 

23cm BFQ68

/bfq68.jpg

 

 

 

 

70cm Pre Amp  (3SK97)

 /img_0484.jpg

 

 

 

 

 

2m Pre Amp  (3SK97)

/img_0485.jpg

 

Inside

/img_0486.jpg

 

 

 

 

Welcome

Welcome to www.sm6why.n.nu.

My Newsletter

Links