On Sun, 10 Apr 2005 20:27:55 -0500, Tom Ring
wrote:

HP ratio meter, 1kHz tone on AM. He thinks the HP is a model 340, but
would have to go out in the garage to look.

Hi Tom,

Not one of their numbers against the characteristics. However, I am
familiar with what you describe as the characteristics.

It is a tuned AC voltmeter, commonly used for SWR measurement in
slotted lines connected to a the detector where the source is
modulated at 1KHz. The meter is tuned to 1KHz and has a very high
gain and selectivity. This allows it to employ a variable gain, by
10dB switch steps (and a variable knob to set zero, or the reference).
The scale is read in combination with the attenuator (gain) switch and
thus the scale offers considerable resolution, easily 0.1dB and
better. It is probably an HP-415.

I've calibrated these too (Boonton, I think, also built them, but as
Boonton was acquired by HP, it isn't a remarkable difference).

73's
Richard Clark, KB7QHC