[TowerTalk] APP issues

[W3YY]

Thanks for mentioning that locking device.  I didn't know they existed.  I
always thought the APP did not have enough retention force when mated and I
assume these locking devices should solve that problem.

73, Bob - W3YY

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of
Howard Hoyt
Sent: Monday, November 17, 2014 3:39 PM
To: towertalk at contesting.com
Subject: [TowerTalk] APP issues

Hi all,

I too use APPs for 12V amateur equipment, however I do have reservations
about them and some work-arounds:

1) Retention force:  When assembled in a pair, the retention force is not
high enough for all uses, lateral forces on the plug are translated by
flexibility of the housing into a rotational moment at the center of the
mated pair, encouraging dismating.  Indeed pushing cables around behind my
K3 I have inadvertently unplugged the DC input.
Anderson makes a locking device:
(http://www.andersonpower.com/files.php?file=02628.pdf)
Powerwerks also makes a retention clip:
(http://www.powerwerx.com/powerpole-accessories/powerpole-retention-clips.ht
ml)
Both of these are very inexpensive, but manufacturers of devices with APPs
must leave the part of the mated pair with the roll-pin hole outside the
rig, and not have installed a roll pin for the locking device to be used.

2) Accidental reverse polarity engagement.  The most common arrangement for
amateur use is a black/red pair side-by-side.  If you are fumbling around
behind a rig with the plug out of sight, there is the possibility of
accidentally plugging the plug one module over, i.e. just the red plug
engages the black jack with the black plug hanging in the air.  If this plug
is coming from your power supply which also has other cables powering
associated equipment, you have just created a short circuit through the
ground circuit of the rig, then through interconnecting cables to other
equipment, potentially burning PCB traces or causing other damage. This
problem argues for recessing the APPs far enough inside a rig panel so that
they can only mate correctly.  Of course then the retainer is unusable.

All of this being said, in general the retention force and reliability of a
15/30/45 pair assemblies is adequate for non-critical use, and they are in
wide use here and elsewhere.  They have exceptionally low contact resistance
and small size for their contact rating and price.  These kinds of
considerations will affect your choice of a connector when manufacturing a
supply: we had considered them for our PAE-Kx33 Power Supply, but decided on
the more direct to KX3 route of a DC Power Plug which, while having higher
contact resistance, is more generic to QRP rigs and also eliminated these
issues.  Of course then we had to offer an adapter for those who needed APP
compatibility!

Cheers & 73,

Howie - WA4PSC
http://www.proaudioeng.com

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