Elecraft PR10 User Manual

ELECRAFT PR10 10-Meter Receive Preamplifier

Owner’s Manual

Revision A, October 20, 2011

Copyright © 2011, Elecraft, Inc. All Rights Reserved

Introduction

The PR10 is a high-performance, low-noise 10-meter preamp that can be used with the Elecraft K3 or other
transceivers. It's especially well-suited for the K3, which has exceptional dynamic range, yet can benefit
from additional gain for 10-meter weak signal work. Adding the PR10 typically improves 10-meter MDS
to -143 dBm. The noise figure of the preamp itself is typically 0.5 dB.

The PR10 can be connected directly to the RX ANT IN/OUT jacks on the K3's KXV3 modu le (required),
where it can be switched in automatically by the transceiver when operating on 10 meters. A second pair of
jacks is provided on the opposite side of the PR10 to allow use of the K3's normal RX ANT IN/OUT signal
path when the preamp is not in use.

Power for the PR10 can be obtained from any 11 to 14 VDC supply. When used with a K3, the PR10 can
be powered from the 12 VDC accessory output. It can be strapped permanently ON, or it can be turned
on/off externally from an open-source/open-drain logic signal. In the K3 case, the DIGOUT1 control line
can be used (on the 15-pin ACC jack), since it is stored on a per-band basis.
The PR10 is housed in a rugged, custom-machined enclosure.

Figure 1. Elecraft PR10 Low-Noise 10-meter Receive Preamplifier.

Elecraft • www.elecraft.com • 831-763-4211

Specifications

Frequency Coverage: 28 – 30 MHz
Noise Figure: < 0.7 dB, 0.5 dB typical
Gain: 18 dB nominal
IMDDR: >100 dB (when used with an Elecraft K3 transceiver)
Power Requirements: 11 to 14 VDC: 13.8 VDC @ 70 mA nominal
Size: Case: 2-1/4” x 2-5/16” x 3/4” (5.72 x 5.87 x 1.91 cm)
Weight 3 oz (90 grams)

Installation and Operation

Elecraft K3

The BNC connector spacing matches the rear-panel RX ANT connectors so the PR10 may be attached to
the K3 using the supplied male-male BNC connectors as shown in Figure 2. A prewired cable is supplied
that connects to the K3 as follows:

 Power is taken from the K3 12V jack on the rear panel: red (12V) to the center pin and black

(GND) to the shell. Power to the PR10 will be switched on and off along with K3 using the front
panel POWER button.

 The Control (CTRL) input is optional (see below) when the DB-15 connector is attached to the

ACC connector on the K3. The white CTRL wire is connected to the DIGOUT1 signal at pin 11 of
the ACC jack on the K3 rear panel through the DB-15 connector (See Figure 2). If you already
have a cable connected to the K3 ACC port for a transverter or band decoder, remove the DB-15
from the cable and add the wire to pin 11 of the existing connector.

Control (CTRL) Input

When the control (CTRL) is used and jumper P2 is removed (see Figure 3), the K3 may be configured so
that the preamplifier is switched on only when the 10 meter band is selected. Since power is switched off
on other bands, the bypass connections are active and the preamplifier does not draw power. Configure the
K3 as follows:

 Select the 10 meter band and then set CONFIG: DIGOUT1 ON. Make sure it is OFF for all other

bands. Note: If a KAT3 ATU is installed, the DIGOUT1 setting will be stored per-antenna (in
addition to per-band). Be sure to turn DIGOUT1 ON only for antennas that require the gain
provided by the PR10. You can tap ANT while you're in the DIGOUT1 menu entry, if applicable.

 On 10 meters, tap RX ANT to enable the preamplifier.

If the control (CTRL) line is not used and jumper P2 is installed (see Figure 3), the PR10 will be switched
into the circuit when the RX ANT button is pressed. The bypass antenna connections are not available
unless power is removed from the PR10.

Page 2 PR10 10-Meter Receiver Preamplifier Owner’s Manual

Other 10-meter Receivers and Transceivers

The cover label on the PR10 identifies the signal, power and control connections.

 The preamplifier is switched into the circuit by applying +12 VDC to the unit if jumper P2 is

installed or, if jumper P2 is removed, by applying +12 VDC and grounding the CTRL input.
Jumper P2 is shown in Figure 3.

 If used at a transceiver RF output, limit the RF power passing through the PR10 to 15 watts in

bypass. RF power must not be present when relays switch.

 The coaxial lines may carry up to 13.8 VDC as well as RF to power an external device when it is

in bypass mode. Blocking capacitors isolate the preamplifier circuit from the d-c voltage.

Figure 2. PR10 Mounted on Elecraft K3.

PR10 10-meter Receiver Preamplifier Owner’s Manual Page 3