Pro Audio Eng PAE-Kx33 User manual

Owner’s Manual
Rev 1.9
November 20, 2017
Pro Audio Engineering
PAE-Kx33 Low-RFI AC Power Supply

Thank you for purchasing the PAE-Kx33 Low-RFI AC Power
Supply.
The Kx33 was specically designed for the needs of high-performance
HF transceivers and communications equipment requiring a low-noise
source of DC. It is perfect for use with any device designed to operate
from DC 12-14 V at up to 4 A.
This supply features an innovative design which inherently minimizes
RFI. In addition the Kx33 features multiple lters to further reduce
emissions. The result is a power supply offering the small size and
light weight advantages of a switching supply without the common
disadvantages of RF noise, poor regulation and others. For full
information on its specications, design and performance capabilities,
please visit: www.proaudioeng.com
We welcome any and all comments regarding the design, operation or
performance sent to: [email protected]
Howard Hoyt
WA4PSC
www.proaudioeng.com
IMPORTANT NOTES:
This power supply must be operated from a 50 Hz ~ 60 Hz power
source between AC 100 V and 250 V ONLY. Operate in an
environment away from direct sunlight or moisture. This supply should
not be used to directly charge a battery, damage, injury or re may
result. Failure to observe these constraints will result in voiding of the
warranty.
Operation:
We suggest you plug the PAE-Kx33 power supply into an AC source
before turning on the attached equipment. If you are using the Kx33
to power more than one piece of equipment at the same time, turn on
the one with the largest power requirement rst. For optimum noise
elimination it is useful to place the supply at the full DC power cord
length away from the rig being powered.
The Kx33 is rated at 4 A output, but will produce considerably
more for a period of a few seconds. This allows it to drive large
capacitances and transient loads without current fold-back.
The Kx33 offers comprehensive protection circuitry including in-
put over and under-voltage, output over-current, over-temperature
and short-circuit protection. These have been incorporated into the
Kx33 to protect your equipment, but they should not relied on as a
replacement for proper wiring or fusing.
At loads less than 25 mA the Kx33 enters a skip-cycle mode in
order to maintain voltage regulation. When in this mode there can be
additional noise on the output. For lowest noise it is recommended that
a load of greater than 25 mA be maintained. This is standard behavior
for most switch-mode supplies.
Some antenna systems, especially end-fed antennas will encourage
common-mode coupling through the power supply. This can
result in an apparent increase in noise, but thanks to the Kx33’s
very low input to output coupling, it is easily remedied by the
use of a common-mode choke. This can be made easily by
running the DC power cable 3-4 turns through the Snap-It core
provided with the Kx33. If additional cores are needed Pro Audio
Engineering offers a range of Fair-Rite products at very low cost:
https://proaudioeng.com/fair-rite-ferrites/
Please read the following section on RFI and AC power
supplies for more information.

AC Power Supplies and RFI:
When powering a DC 12 V receiver from an AC line power source
you may occasionally nd the receive noise oor becomes
contaminated with noise of various sorts which are not present when
powered by a battery and isolated from the AC power system. It is
tempting to believe that all of the additional noise originates from
within the power supply, but when using the Kx33 this is seldom the
case. It is a common misconception that all linear power supplies
powered from the AC mains are as quiet as batteries and all
switching power supplies are noisy. The truth is more complicated
due to the multiple routes by which RF Interference (RFI)
can be induced into a receiver. The main routes for RFI are:
1: Transverse or Differential-mode conduction of RF ripple
superimposed on the DC power supply output can introduce RFI into
the equipment being powered. It is critical for the designer of a supply
to resolve this source of noise inside the supply as it can cause
radiated RFI if allowed to propagate on the DC power cord. We
specically designed the Kx33 to have extremely low RF ripple on the
DC output and to date have not had any of this type of RFI reported.
2: Common-mode coupling of the antenna system to the AC
power line through a power supply can introduce several types of RFI
to sensitive receive systems. This potential exists between the AC
input and DC output. Whether this coupling introduces noise depends
on two main factors:
a. The AC input to DC output impedance of the power supply.
All AC line powered supplies have capacitive coupling between
the AC line and the DC output. This can be a path for RF energy
to take if a difference in potential exists between the two.
When using a linear supply the instantaneous input to output
impedance will be modulated at the AC line frequency, leading
to the hum commonly heard in older single-conversion receivers.
When using a switching supply the coupling can be modulated
by the dynamic impedance of the switching action and can
cause RFI. Measurements taken of many power supplies by PAE
show linear and switching supplies offer ~1000 pF of capacitive
coupling on average. At ~70 pF the Kx33 greatly minimizes
this coupling and the magnitude of this common-mode RFI current.
This makes choking common-mode currents much easier with the
Kx33 than other power supplies.
b. Balance and common-mode potential of the antenna system.
If the antenna system has a current imbalance between the
main radiator and counterpoise or two halves of a dipole as many
temporary antenna systems do, it will force the imbalance current
back down the outside of the coax feedline shield making it an
active part of the antenna system. This will affect the antenna
pattern in receive and transmit as well as allow the feedline to
receive ambient noise. The rig chassis, the power supply and
AC mains are then all in a series path for these common-mode
currents making them an active part of the antenna system as well.
Inserting a common-mode choke in the antenna feedline at the
a nte n n a feedp o i n t is t he best w ay t o r e d uc e o r e l i m inat e t h is c o m m o n -
mode current ow. An excellent reference on this subject can be
found on K9YC’s site: http://audiosystemsgroup.com/RFI-Ham.pdf
For cases where an antenna system may present common mode
potential we include a Fair-Rite mix 31 Snap-It core which can be used
to make a choke by winding the DC output cable of the Kx33 through
the core 3-4 turns. This will effectively increase the common-mode
impedance through the Kx33 by 800 to 1000 ohms @ 10 MHz,
effectively minimizing this current path through the supply. If
additional ferrite products are desired we offer a range of
Fair-Rite Ferrite Clamp-On and toroid cores at low cost to
our customers at: https://proaudioeng.com/fair-rite-ferrites/ We
made the decision not to integrate a large ferrite choke like the
included Snap-It core inside the Kx33 in order to minimize size and
weight. For 99% of all users, the RFI performance of the Kx33 itself
will be sufcient, and if additional common-mode choking
is required the additional core can be employed.
3. Radiated RFI can come from many sources and can be
picked up by the antenna system or many other cables with poorly
designed shield terminations and appear as a signal in the
receiver. In a well-designed supply like the Kx33, the external elds

33-160 - PowerPole to Female DC Adapter
Adapts the output of the Kx33 for use with
any DC 12 ~ 14 V device requiring a PowerPole
connector such as the Elecraft K3/10 and others.
33-165 - PowerPole to Male DC Adapter
Adapts any PowerPole DC 12 ~ 14 V source to power
an Elecraft KX1/KX2/KX3 or other device
needing a 2.1 mm x 5.5 mm DC power plug.
33-180 - 28-piece DC Power Adapter Kit
Adapts the output of the Kx33 for use with
almost any device requiring DC 12 ~ 14 V
power at up to 4 A.
Fair-Rite Ferrite Mix 31 Cores
Useful for choking common-mode RFI from RF and
power cables.
33-400 - Snap-It (0.933″OD x 0.4″ID x 1.55″L)
33-405 - Snap-It (1.22″OD x 0.514″ID x 1.55″L)
33-410 - Snap-It (1.52″OD x 0.722″ID x 1.87″L)
33-420 - Snap-It (2.22″OD x 1.01″ID x 1.69″L)
33-430 - Toroid Core (2.4″OD x 1.4″ID x 0.5″L)
33-440 - Toroid Core (4.0″OD x 3.0″ID x 1.0″L)
33-510 - Right Angle AC Adapter
Replaces the Kx33′s AC cord, allowing the Kx33 to
be mounted ush to the wall supported by the AC
plug, eliminating the clutter of an AC cord.
See https://proaudioeng.com for more information and accessories.
from the high-current PCB loop between the switching devices and
transformer, and the elds of the transformer itself are extremely
small. In order to minimize the pickup of any radiated RFI we
recommend placing the supply the full length of the DC supply
cord away from the rig. Another excellent paper on Jim Brown
K9YC’s site shows how improper cable termination or chassis
grounding of connectors can allow radiated RFI to conduct into
our systems: http://audiosystemsgroup.com/PAARA-RFI-2011.pdf
We are sure you will be happy with the Kx33 or we will refund both
your purchase and shipping costs. There is no risk other than a small
amount of your time evaluating it.
Maintenance:
Clean with a dry cloth, use no solvents, cleaners or water. There are
no adjustments inside. If the supply is not performing as expected,
please contact us at: [email protected]
Accessories:
33-100 - KX3 & PX3 DC
Power Splitter Allows you to
power the Elecraft KX3 and
PX3 from one Kx33 AC Power
Supply.
33-120 - 4.0 mm x 1.7 mm DC Power Adapter
Adapts the output of the Kx33 for use with the
Yaesu FT-817 and others.
33-140 - 5.5 mm x 2.5 mm DC Power Adapter
Adapts the output of the Kx33 for use with the
Flex1500, Softrocks and others.

Specications:
Input Voltage: AC 100 V ~ 250 V, autoswitching
Input Current: 0.7 A : AC 115 V full-load,
0.3 A : AC 230 V full-load.
Input Frequency: 50 Hz ~ 60 Hz
Output Voltage @ plug (+/- 0.1V): DC 14.4 V no load,
DC 14.2 V at 0.2 A load,
DC 14.0 V at 3.5 A load.
Output Voltage as shown in Elecraft KX3 (+/- 0.1V):
DC 14.2 V receive at 0.2 A load,
DC 13.6 V transmit at 2.4 A load.
Output Current: 4 A maximum continuous, 5 A for 30 seconds.
Maximum Ripple: 10 mV (30 MHz BW).
Protection: over-voltage, over-current, over-temperature,
short-circuit.
MBTF: >50,000 hours.
Approvals: UL, FCC GS, TUV, CE, PSE, KC, SAA, CCC
Dimensions (excluding cables): 2″ x 1.25″ x 4.5″
(50 mm x 32 mm x 114 mm)
Cable Length: AC line cord - 58” (1400 mm),
DC power cable - 78” (2000 mm)
Weight: supply: 9.3 oz (264 g), AC cord: 3 oz (85 g),
total: 12.3 oz (349 g)
Warranty: 1 year from date of purchase.
©2017 Pro Audio Engineering