Wireless Set No. 19 Aerial Variometer

This is a very nice Wireless Set No. 19 Aerial Variometer, dating to WW2.

In good, but slightly dusty, condition with surface scuffs and scratches commensurate with age and use. The glass is missing over the scales. It would have been used in conjunction with the British Wireless Set No.19 (not included!)

The Aerial Variometer was used to match a short rod aerial of 8 or 12 feet to 1/4 wavelength in the frequency range of the Wireless Set (W.S) No. 19 (see schematic below).

Two calibration scales are available 0-100 and 200-100. Both are accessible by turning the control knob on the variometer by 180 degrees for one scale and another 180 degrees for the second scale.

• The 0-100 calibration is used at low bands frequencies (2-4.5 MHz). The two coils are switched in series with the addition of inductance.
• The 200-100 Calibration is used at the higher band (4.5-8 MHz). In this configuration the coils are switched in parallel with reduced inductance). 

Variometers normally should be the same Mark as the Wireless Set No. 19 e.g a MkII with a MkII, however, the MkII can be used with a MkI and MkIII with some modifications to the R29A resistor.

For more information see L. Meulstee Wireless for the Warrier pages: W.S.19-27 

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