Got a phone call a week ago from a VK5 ham looking for a devoted 28mhz amplifier..Well, I completed it yesterday and ready to be sent off...This is one of my standard jobs using a pair of Russian GI-7B triodes along with an Antek toroidal HT transformer that delivers 2500vdc @ 600ma...I fired it up today and it easily gives 800 watts carrier output so has ample headroom for the VK 400 watt power limit...
Playing around with it this evening I find it also easily tunes up on the chicken band 27mhz right up to 29mhz ....I cheated a bit in the construction as I had a spare 50mhz chassis and front panel already completed so that gave me a head start....I used an old Hammalund WW2 tuning cap in the anode tuning and a shunted Millen cap for loading with some 1/4 inch plated stock for the coil...
Now I wouldn't purposely build a 27mhz amplifier but quite surprised how easy it is to do.. The new owner takes delivery next week and now wants me to build him an 833A 196khz VLF amplifier...In VK we have an allocation down there apparently...I will let you all know when I start into that job, it's a challenge and I will have to source some information on VLF amplifiers....
Enjoy these pics...
Bob..VK3ZL..