                         Sherwood Engineering, Inc.

                           1268 South Ogden Street
                              Denver, CO 80210

                         E-Mail robert@sherweng.com
----------------------------------------------------------------------------

                           SE-3 MK III D (Deluxe)
               High-Fidelity Phase-Locked AM Product Detector

              Eliminates Selective-Fade Distortion and Garbling
      Able to Receive One Sideband at a Time to Minimize Interference


Introducing a whole new world of shortwave and broadcast reception with the
new Sherwood SE-3 Mk III phase-locked AM product detector. Even with the
evolution of modern-day communications receivers, with their improved
stability, selectivity, and dynamic range, AM reception under fading signal
conditions has remained a compromise. With a diode or synchro-phase
detector, severe distortion occurs every time the carrier drops out in a
selective fade. Carrier nulls (fades) of 20 to 30 dB or more are common,
which result in total loss of intelligibility. Under these conditions, the
desired signal has become a double-sideband reduced-carrier transmission
which cannot be detected in the normal manner.

Exalted-carrier selectable-sideband (ECSS) reception can be used to combat
the fading problem. Distortion is not present, (assuming a properly
operating receiver/detector), but a beating problem occurs because you
cannot keep the receiver right on frequency. In effect, one type of
distortion is traded for another. (Even a synthesized receiver, tunable in 1
Hz steps, would be mistuned a fraction of Hertz, resulting in a swishing
sound every few seconds.) While tuning errors of some tens of Hertz may be
tolerated during voice reception, music sounds more unpleasant because the
harmonic relationship so critical to musical overtones is destroyed.

The only complete solution to the problem is phase-locked detection with a
product detector. The BFO in the SE-3 is locked to transmitted signal's
carrier, and then completely replaces it in the detection process. Thus
demodulation is fully independent of the signal's carrier strength at any
given moment. A selective null can roll through the signal, changing the
tonal balance of the audio, but proper detection will still take place.

The SE-3 is a self-contained buffer, detector, and audio amplifier system.
All that is needed is an i-f output (from the receiver) and a speaker or
headphones. The amplifier is rated at 5 watts, and is adequate for most
installations. If a low efficiency acoustic-suspension speaker is preferred
for music reproduction, an auxiliary output is provided for an external
amplifier. Tape recordings can also be made from this output, if desired.
The headphone jack will accommodate either mono or stereo phones without the
need for an adapter.

The SE-3 has two main front-panel controls: A PLL (phase-locked loop)
control and audio gain/power on-off. Infinitely variable for the equivalent
of passband tuning from LSB to USB, or anywhere in between. Any filter
bandwidth is usable from 1.3 kHz to 8 kHz on standard units. An AM / SSB
switch is provided for SSB/RTTY/CW reception.

                    The Following Features Are Included

   * Audio notch (whistle filter) at 5kHz is optimized for shortwave channel
     spacing.
   * Synchro-phase (envelope) detector for conventional operation or rapid
     scanning. Allows SE-3 output to be used at all times.
   * High-frequency roll-off and boost tone control to compensate for
     poor-quality program material or to correct for speaker roll-off. Three
     positions: flat, 5 dB boost at 5kHz, or 5 dB cut at 5 kHz.
   * Flutter filter for multi-path and time delay distortion.
   * Buffered auxiliary output for recording or driving other accessories.
   * Guide lock switch for manually guiding the PLL into lock.
   * Bass boost tone control for 8 dB boost at 100 Hz.
   * Manual BFO for SSB reception. Available with fixed offsets (LSB/USB or
     manual BFO knob if desired.

SE-3 MK III D (Deluxe) $495.00 US
Shipping UPS $15.00 US
Overseas airmail $45.00 US
Overseas insurance $10.00 US

   * Rack mount option: 3.5-inch rack mount faceplate instead of cabinet is
     available for an additional $95.00 US

A transformer, with cable and mating connector, is supplied with each SE-3
for operation with 120 V. AC mains. Transformer supplies 20 V. AC at 1/2
amp.

Please specify receiver model or IF level if known.

System bandwidth is determined by receiver i-f bandwidth:
6-kHz filter would give response to 6 kHz when run with full LSB or USB
offset.
SE-3 response: 30 Hz to 15 kHz at -3 dB.
SE-3 IF input requirements: 30 mV. to 2V. RMS at 455 kHz.
Speaker impedance: 4 ohms or greater.
Auxiliary output: 300 mV RMS.


                              Comments on SE-3

A receiver that has been modified to operate with the SE-3 is not affected
in any way for normal operation. We simply add an IF output to drive the
external SE-3 detector / amplifier.

Some radios will require a converter to down convert (or up convert) the
last IF to 455 kHz, the input needed by the SE-3

The crystal-controlled converter board sells for $95.00. Installation is
$45.00 if done at Sherwood Engineering in Denver.

Converters have been used with the following radios: Icom R70, R71, & R9000.
Kenwood R-5000, Drake R-7. The converter for the R-7 is in an external
shielded box and is $195.00.
