[Amps] Microwave oven door glass - shielding?

[Jim Barber]

Hi Ron,

On 10/21/2013 7:05 PM, KA4INM wrote:
>    On 10/21/13 18:15, Jim Barber wrote:
>
>> Has anyone had experience using microwave oven door glass as a shielded
>> viewport for an HF amp? Any ideas about attenuation at HF frequencies?
>
>> I'm considering a three-tube 3500ZG amp as one of my winter projects,
>> and was thinking it would be fun to show the tubes with their cheery
>> cherry glow.
>
>    How may output Watts will you be producing?
>    (or are you just going to detune the plate until everything turns red)

375 watts carrier, 1500 watts PEP. That will get 2 tubes orange with any 
compression at all. I was thinking 3 tubes because 2 seems to be close 
to the edge for true legal limit operation. Two would be easier to deal 
with from the filament  transformer and choke side, that's for sure.

> >    My mw ovens have a steel plate with a bunch of holes in it behind the
> glass to block the RF, this shouldn't be much of a concern at 29 MHz and
> below.

I have a couple of different kinds here. One has a wire grid that is 
either embedded in the glass or sandwiched between two glass sheets. The 
large in-wall unit is something like you describe, except the perforated 
metal appears to be between two glass sheets. I'm thinking either type 
would work with some kind of clamping bezel, assuming I can duplicate 
how they're grounded to the door metal.

Thanks and 73,
Jim N7CXI