400 mw VHF amplifier

Hi John,
There is a lot of info on the pages. HHH was originally my lab-book with circuits and ideas. Instead of writing everything in a notebook, then losing the blooming book, I started HHH and put all my useful experiments and notes there.

The generic VHF PA pages was among the first to be recorded so I could refer to them myself  

Another page that could be of interest is calculating the input and output matching circuits:
http://213.114.137.174/blocks/transistors_match_00.htm
http://213.114.137.174/tx/vhfpa-00.htm

Incidentally, HHH is located at www.sm0vpo.com or http://213.114.137.174/
Altervista is a mirror site that I can also easily modify, especially when I am not at home. www.sm0vpo.com is a RaspberryPi on my bedside table. All the 16,000 pdfs in the datasheet library are there.

Another advantage is that from home I can simply SSH to the machine to edit the pages in Linux, using GEDIT or VI. I can also FTP files to and from the machine and the changes take immediate effect.

Very best regards from Harry - EA/SM0VPO

Digging further today I found a link where Harry already addressed a linear VHF PA!
http://sm0vpo.altervista.org/tx/vhfpa-00.htm

Thanks Harry!

John
KC9OJV

HRouse wrote:In Class C mode the amp is stable, but as you convert it to class A it becomes less stable,thermal runaway is the main cause. Class B  would be a better option as it still has some bias, but room for thermal effects

Thanks for your comments. I think that if I end up using a push pull design I might as well take it to class AB but I'm going to try converting Harry's design to Class A first. I didn't know much about Class B and it's an interesting design so thanks for mentioning it!

John
KC9OJV

In Class C mode the amp is stable, but as you convert it to class A it becomes less stable,thermal runaway is the main cause. Class B  would be a better option as it still has some bias, but room for thermal effects

I'm hoping to be able to run Harry's 400mw VHF Class C as Class A with a fixed bias added. Looking at the example of Class A circuits it looks like I should be able to add bias resistors R1 and R2 (from the Class A example- not R1 and R2 on the 400 mw design) at the grounded side of the transformer T1 and add a capacitor C2 parallel to R2. I'm not sure how to calculate the proper values for these components and maybe it's not that simple?

Thanks for your help,

John
KC9OJV