On Wed, 14 Sep 2005 09:14:26 +0200, "Markus L"
wrote:

"Jim" wrote in message
...
Most power MosFets have a large Gate to Source capacitance which makes
it
difficult to use them at radio frequencies.

It can be done, but the higher the desired operating frequency the
greater effect the parasitic capacitance has, so most designs I have seen
were up to 7 MHz and that was about the upper limit.

A German ham radio magazine just published a project for a 400W MOSFET PA
covering the 80...20m bands:
http://www.vth.de/FUNK/funk/09_05/28.asp

Markus HB9BRJ


Yes but were they class E or linear? There are a number of AM ops on
160/75/40m running 1kw AM phone using class E FET. However class E
for 6M I havent seen yet. The german design would not run at 6m and
thats what the initial posting asked for.

Those power fets at lower frequencies are a very useful devices but at
VHF their characteristics are difficult to accomodate.

Allison