[ARC5] Re: [Milsurplus] RF Ammeter Puzzle

[J Forster]

Bob Miller has kindly pointed out to me that the ARC-5 meter is NOT
calibrated in Amps, but in arbitrary units. Mystery solved. Thanks.

I don't understand "0-0.25 amperes with a 20X expanded scale".  Do you mean
the meter movement is 0.25 A DC and the TC produces .25 A in the meter DC
circuit with an RF current of 5 A ?

The 1:1 transformer is clearly a current transformer, used to isolate the
meter guts from the high RF voltages on the antenna line (as in the BC-442).

Best,
-John



Bruce MacMillan wrote:

> Hi John,
>
> In the art13 manual, T.O. 12R2-2ART13-2 dated 30 March 1956, the rf
> ammeter (M101) is a GE 8DW52AAR84. It is an internal thermocouple type,
> 0-0.25 amperes with a 20X expanded scale. Freq range is 0-20 Mc. It is
> coupled to the output of the antenna vacuum relay by xfmr T102 which is
> used as rf meter coupling. No specs on the coil other than iron core,
> single turn primary, single turn secondary.
>
> Bruce   ve7mt
>
> J Forster wrote:
>
> >I have come across a puzzle on RF Ammeters.
> >
> >The ART-13 uses a TC meter with 5 A FS and the ARC-5 uses a TC meter
> >with 10 A FS, yet the ART-13 is a higher power Tx. There is a current
> >transformer in the ARC-5's BC-442, but it seems to be a 1:1 ratio.
> >
> >Is the RF Ammeter in the ART-13 somehow not in the antenna line (but at
> >some higher impedance point in the circuit) ? I don't have ART-13 prints
> >to hand
> >
> >Best,
> >-John