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** Begin preachy statement:

First things first, since there is a lot of misinformation floating around
about the proper mating of APC7 connectors, I will start there. Before
you mate an APC-7 connector, wipe the mating surfaces with a clean rag
dipped in 99% isopropyl alcohol... cleanliness is paramount if you want
repeatable measurements.

When you mate an APC7 connector, one of the two connectors should have
its outer collar turned until the center threaded sleeve is all the way
exposed. Then holding the other connector (so that its insides cannot
rotate), engage the threads on the sleeve, and tighten until finger snug.
Do not under any circumstances allow the two connectors to rotate relative
to each other!

Over tightening the connector will cause the gold on the face where the
two shields mate to swage out, making a tiny annular choke ring in the
shield, destroying the RF characteristics of the connector.

If the sharp ridges on the connector shell are cutting your fingers, it
is too tight!

Do not snug up the loose outer collar into the tight outer collar.
Doing so will confuse you when it is time to unmate the connector, and
can lead to operating with a loose connection.

** End preachy statement.

The important RF goodies of an APC7 connector are designed to be field
replaceable from the outside of the instrument. If you look at the
face of the APC7 connector, you will see two drilled holes,
diametrically opposed, on either side of the gold coaxial shield. The
holes are placed there for engaging the pins on a spanner wrench used
to tighten/loosen the APC7 connector to the chassis mounted part of
the connector. Make sure that the disk they turn is not loose... it
is probably ok, if you aren't seeing massive changes in reflection and
loss when the connector is wiggled.

And lastly, the chassis end of the connector is usually held to the
chassis by a large threaded nut, just like most other RF connectors.
The connector passes through a "D" shaped hole, which is why it won't
turn, and the nut holds it tightly to the chassis.

Sometimes, when the APC7 is feeding a stripline on a circuitboard,
the chassis box is the other side of the connector, so in that case,
the threads that the spanner wrench holes turn are all that holds
the connector onto the chassis.

A good source of replacement APC7 connector ends is a burned out APC7
type of attenuator... it is of zero value as an attenuator, but the
APC7 connector ends can be removed with a spanner wrench, and used
on something more important to you, such as a 8753D.

-Chuck Harris

fishtronics wrote: