"Walter Maxwell" wrote in message
...
On Mon, 30 Aug 2004 01:04:57 -0400, "Tim Perry"

wrote:


"Walter Maxwell" wrote in message
.. .

snip

I was just about to tell you what I use, but Richard, above, beat me to
it. For
HF measurements this bridge, the General Radio 1606-A, is the Cadillac
of
all
bridges. It 's been the bridge of choice for nearly every AM broadcast
engineer
in determining t he impedance of AM broadcast antennas since it came on
the
market in 1955.

i have yet to see one at a US broadcast station. the meter that is
usually
found, and used is the delta OIB-1 or OIB-3
http://www.deltaelectronics.com/data/oib1&3.htm

Hi Tim,

I can't disagree with you here, because my knowledge is from several years
back.
I'm not familiar the Delta except by reputation--all I've heard is that
it's a
good instrument. The demise of General Radio is probably one reason the GR
instrument is no longer the instrument of choice, so the dividing line
between
use of the GR and the Delta probably defines the end of one era and the
beginning of another.

Walt, W2DU

in part, the OIB (Operating Impedance Bridge) is popular because the normal
transmitter is the (usual) frequency source and interruptions to
transmissions can be brief or non-existent.
in typical use the bridge is inserted using a hot jack or J plug.
the engineer must be careful at all time to avoid touching exposed RF as the
resulting burns are painful and long lasting.
the meter itself has some effect on the circuit tuning: sometimes a
permanent version is installed at the common point of a phased array.
sometimes special jacks are employed that add a bit of inductance when the
meter is removed.