[AMPS] blocking cap current

[Rich Measures]

>
>Rich says:
>
.........
>>During the grate parasitics debate, when we were discussing
>> gold->evaporation from an 8877's grid, I showed that RF grid-current in an
>> 8877 >(operating at its max. ratings of 4kV and 250MHz) exceeds 43RMS
>>amperes.   
>
>This does suggest why you can get troubles with poor grid grounding
>techniques. Does the 8877 have a grid ring for a collet, 

€  Yes.  Eimac makes a grid collet grounding device that has minimal L.  
>.........
>Even a 3-500Z would appear to have 1.8 amps of RF in its grid connection at
>28MHz. This suggests to my mind that something better than disc ceramic
>capacitors ought to be used to bypass the grid.

€  Kenwood, Heath and Drake used three, paralleled 500v mica capacitors 
that were not current rated.  It worked ok.  

>I suppose that you can get away with a lot on SSB, but SSTV or RTTY really
>separates the men from the boys when it comes to reliability.
>
€  Continuous is way different from SSB's 15% avg, duty cycle.  
>
-  cheers, Peter


Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


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