Sunday, January 22, 2017

Triband 6/4/2m Amplifier finally finished

Last Summer, browsing ebay, I found a Kalmus 172F wideband amplifier. "Kalmus broad band vhf power amp model 172F High gain 200 watts rf output <1w @ 50-100mhz <4w @ 144mHz, on the tin it does say 80-160Mhz but it does cover 50-70MHz, supply required 28 volts dc 14 amps" Looked Interesting so I bought one

In the last few weeks finally got around to using it. I wanted it to be smaller than it's bigger brothers so i managed to squeeze it into a 12x7x3" box. No room for low pass filters so they have to be plugged in externally. A PIC oversees the amplifier and displays status on a front panel 20x4 LCD.

The kalmus amplifier already has a bridged T input attenuator, so I increased it by 3dB so I can drive it with the 7W from the anglians / nactons on 4/2m and 8W from the K3 on 6m. On all bands it produces over 200W


  1. Is this definitely a class AB amp?


  2. Its at least class AB; closer to class A with 3.5A standing current. Kalmus produced many amps for the usa military with stringent linearity/widebandwidth requirements