Re: [Amps] DVM recomendation

["Ian White, G3SEK" <G3SEK@ifwtech.co.uk>]

R. Measures wrote:

G3RZP had written:
> > If you are looking to do measurements round an amplifier when there's 
> > RF
> > around, get an analogue meter!
> >
> > I haven't found a digital voltmeter yet that behaves with a lot of RF
> > around.
>
> ð  Peter -- My Fluke DMM does OK with a bypass C on a double-banana 
> plug inserted between the DMM and the test leads.  However, I would not 
> use a digital meter in a tetrode-with-handles amplifier project.

RF immunity is a lottery. You don't always get what you pay for... but 
sometimes you can also get lucky.

I was reminded of this recently when working on someone's large 
two-holer (no handles, but definitely two heavy handfuls) that uses my 
Tetrode Boards. His whole shack was crawling with RF, but my two cheap 
DMMs measuring the grid and screen voltages both sat there serene. Just 
lucky for once, I guess.

Hopefully I've persuaded him that the "classic ham radio" shack layout - 
open-wire feeder all the way into the shack, breadboard ATU and 
unshielded amplifier - is NOT suitable or safe at these power levels!


--
73 from Ian G3SEK

http://www.ifwtech.co.uk/g3sek/boards
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