[Milsurplus] more / Fw: [ARC5] RF ammeters / BC442-A ...

[Henry Frederick "Meils" Meiseles]

I take it for granted that any fuse designed for RF purposes would have to 
take into account
skin/surface conduction contra frequency. Another possibility might simply 
be a series connected
light bulb of appropriate rating where brilliance would indicate aprox. 
current and  could be
be switch-bypassed where brilliance seems within limits. Pretty certain this 
was used on
some maratime transmitters. I'm aware that the resisitance of any series 
connected bulb will
influence the RF current flow, which will of course change, when the bulb is 
bypassed,
but visual light assesment this a matter of approximation.

HFM, Cph.



----- Original Message ----- 
From: "Henry Frederick "Meils" Meiseles" <meils at get2net.dk>
To: <milsurplus at mailman.qth.net>; <arc5 at mailman.qth.net>
Sent: Friday, May 27, 2011 7:45 AM
Subject: [ARC5] RF ammeters / BC442-A ...


>I have two type "ANTENNA RELAY UNIT BC-442A," of which one is functional.
>
> Is the 1 - 10 scale arbitrary or is it  actual/real amperes of current?
>
> 10 A seems like a lot for rigs in the 25-40 watt output class but 
> considering
> how often RF ampere meters burn out because of short period mismatches,
> this might well be an intentional protectional "overshoot." Were these 
> ammeter
> units also used for higher power rigs? The ART-13 has an RF ammeter of 3A,
> if I remember correctly, even though it could deliver considerably more
> than a Command transmitter.
>
> A quick comparison did show "1" when 1 A was read on a second
> series connected RF ammeter.  -- I could rig it to my RF wattmeter but
> at present cannot generate more than 100W RF out to the 50 ohm dummy
> load --- which would only yield 1.41 A, anyway.
>
> I don't know if my -442A is reading out as it should but I do get about 
> 1.5 A
> at 100W out into 50 ohms, which is close to the theoretical value.
>
> Since RF ammeter burnt out is a common problem, (I assume some on the list
> will object to this claim). What about fusing them ?
>
> (Yes, I can always run my TCS transmitter output through my 442-A,
> and maybe will do so.)
>
> I have some ideas using a different principle for RF current out readings.
>
>
> Henry, Cph.
>
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