A #47 or similar panel lamp in a holder attached to a couple of 12" pieces
of insulated wiring (usually on the end of a stick) was a pretty common RF
indicator way back when. We also used an NE2 or NE51 neon bulb as a glow
indicator for RF.
It took more power to make the neon bulbs strike, but there was less danger
of getting a little close to the feedline and burning out a bulb. That was
important when there was no Western Auto within a hundred miles. And the speed
limit was a roaring 30 MPH and few drivers made the limit!
Yes, you could use two to indicate relative current in open wire or twinlead.
However it was my experience then that while every bulb in a box would be
equally bright with 6.3 V across them they varied widely at lower voltages.
Being
curious, I just tried a dozen 12.6V lamps with 5.0 V and there is also quite
a range of brightnesses. At least, according to my ancient Cooke extinction
photometer.
Anyhow, I haven't tried that in years - since I have boxes with meters on
them that do the same job - but if I were trying that again I would use two
bulbs with identical length pickup leads and turn it around at every maxima
and
minima. Do remember to keep all hands away from the transmission line. RF
cooks flesh and you don't want to barbecue yourself. It hurts like blazes and
far
longer than a hot grease burn.
73 Pete Allen AC5E
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