[TenTec] balanced feedline light bulb test

[K. Indart]

Hi,
You don't want electric bulbs in series with the feedline.   But you can use
Nr. 47 lamps (Radio Shack has them) and use about 6 inch leads on each side
of the bulb.  Then place the lamp in PARALLEL with the lead.  Use the same
on the other lead at the same place on the feed line.  The further apart
that the leads are connected, the greater will be the voltage and the
brighter the lamps will  be.  Once you have the spacing of the wires for a
normal glow, at the power you normally use, you can leave them connected.
Ken, WA4RPH

-----Original Message-----
From: tentec-bounces at contesting.com [mailto:tentec-bounces at contesting.com]On
Behalf Of Rob Atkinson, K5UJ
Sent: Tuesday, July 15, 2003 1:35 PM
To: tentec at contesting.com
Subject: [TenTec] balanced feedline light bulb test

Al,

I'm a dim bulb (ha ha).  What I think you are saying is get two plain old
regular incandescent light bulbs, open up the feedline and connect each one
in series with it, one on each side to force rf current through the
filaments.  Do I have this right?  the part about spacing alligator clips is
throwing me.  don't see why that matters as long as the connection on one
side is the same on the other.

thanks,

Rob
K5UJ



One extremely easy way to check current balance in the two wires of an open
wire feedline which is used with balanced tuners is the following.

Connect two pieces of about 12 inches of wire to a twist-on holder for a
type 43 light bulb. Attach an alligator clip to the far end of each wire.
Make two such assemblies.

Connect one light bulb to each feedline wire. Start with connecting the two
alligator clips close together and gradually increasing the spacing along
the feedline until they start to glow with transmitted power.  Make sure the
spacing is equal on both feedline wires.

You may have to increase the length of the connecting wires to the light
bulbs or alternately, change the transmitted power in the feedline until you
get a good indication.

It is easiest to judge equal intensity if the bulbs just start to glow.

CAUTION: Turn OFF the carrier when adjusting the clips along the wires!

Intensity of each light bulb indicates current in the feedline. If both
bulbs light equally then you have a good balanced feedline with equal
currents in each leg.

It's an old 1930's trick before the days of RG-8 and when RF meters were too
expensive for most hams.

73. Al, w6wqc

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