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Re: JUMA PA1000 Linear Amplifier

These kind of clean symmetrical signals need a proper phase reversing transformer from drain to drain to maintain a good voltage swing in drains. A MOSFET drain or a BJT collector can only pull, they are not capable to push. Actually push-pull BJT transistors or MOSFETs do not exist Tnx for showing...
by vk4dd
20 Jan 2012 04:48
 
Forum: Juma Discussion
Topic: JUMA PA1000 Linear Amplifier
Replies: 50
Views: 92830

Re: JUMA PA1000 Linear Amplifier

Hi Matti, Allow me to give you some more ideas. There is no need to have exactly a 50 Ohm match just behind the transformer on all bands. You can use the band filter and tweak the impedance of say the 6m and the 160m filter a bit . Example. If your transformer has a lower impedance of say 30 Ohms on...
by vk4dd
24 Dec 2011 07:15
 
Forum: Juma Discussion
Topic: JUMA PA1000 Linear Amplifier
Replies: 50
Views: 92830

Re: JUMA PA1000 Linear Amplifier

Hi Matti, From what I understood is that the gate is not the problem with the BLF578 (you can calculate what voltage it can handle and what associated power level that is). More likely the failure would be thermal. The BLF578 is not near saturation at 1 KW and keeps going, so you end up blowing up t...
by vk4dd
24 Dec 2011 03:37
 
Forum: Juma Discussion
Topic: JUMA PA1000 Linear Amplifier
Replies: 50
Views: 92830

Re: JUMA PA1000 Linear Amplifier

Hi, Great respect for the positive work Juha Niinikoski and Matti Hohtola are doing. It has been a joy to read about their projects and designs. I am very impressed by how the kits are put together and it looks like perfection into the smallest detail. The PA1000 from JUMA is I think the first of it...
by vk4dd
23 Dec 2011 00:30
 
Forum: Juma Discussion
Topic: JUMA PA1000 Linear Amplifier
Replies: 50
Views: 92830

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