[ARC5] RF ammeter

[Mike Everette via ARC5]

If this is a Westinghouse meter about 2-3/4 inch body diameter, it sounds like it could be the one from the HF transmitter section of a GO-9 or TBW.  Those meters have an internal thermocouple.

The meters in those transmitters were mounted behind the metal front panel on a piece of micarta or micalex, to insulate them from the actual aluminum panel.  There was a clear glass "meter face" matching the size of the meter itself, mounted to the actual radio panel in front of the RF ammeter.

This mounting method was probably to keep the RF from arcing through the meter case to the metal panel.

I'd be wary of mounting one of these meters in a steel panel or box because its calibration would be adversely affected.

73

Mike
WA4DLF
--------------------------------------------
On Mon, 8/4/14, Kenneth G. Gordon <kgordon2006 at frontier.com> wrote:

 Subject: Re: [ARC5] RF ammeter
 To: "ARC-5" <arc5 at mailman.qth.net>
 Date: Monday, August 4, 2014, 7:29 PM
 
 On 4 Aug 2014 at 19:15,
 Robert  Eleazer wrote:
 
 > I have an RF ammeter if anyone needs
 one.  It is "U.S.N. Type CAY22026A, Type
 > NT-33, 25 cycles to 20MC."  However
 it reads 1, 2, 3, 4, 5, and I guess that is
 > whole amps.
 > 
 > I picked it up at a local hamfest for very
 little, on some club's bargain table.
 >  (I think they may have been the same
 guys I bought a Heathkit SG-6 from for
 >
 $1.50 a few years before, which indicates some degree of
 insanity).
 > 
 > Would
 this have a thermocouple in it?
 
 There were generally two types: 1) those with
 the thermocouple inside the 
 meter, and 2)
 those meant to be used with an external theromcouple.
 
 All those which were meant to
 be used with an external thermocouple were 
 usually marked so on the face of the meter or
 on the case.
 
 I am betting
 yours has an internal thermocouple.
 
 Ken W7EKB
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