Revisiting the Realistic PRO-2006

Around 1990, Tandy Corporation introduced the Realistic PRO-2006 programmable scanner. It was manufactured for Tandy by General Research of Electronics, Inc. (GRE) in Japan. It is also known in Europe as the Commtel COM-205 or Handic 0080 (below), according to Javiation.

Handic 0080 aka PRO-2006 © 2011 Wanderlinse

This triple conversion receiver offers microprocessor-controlled VHF, UHF and FM reception. A rooftop antenna or whip (supplied) is connected via the BNC antenna connector. The scanner sold for a retail price of $400 in the United States.

Realistic PRO-2006 © 2014 FM DXing at WordPress

There are plenty of modifications that can be undertaken for this scanner. These include the ability to tap the discriminator output or the 455 kHz third Intermediate Frequency (IF) signal for SSB demodulation. An HF receiver or modern outboard conversion hardware (such as RadiØKit-2 in combination with open source Dream software) is required to demodulate the SSB from the IF signal.

Being relatively lightweight, the PRO-2006 offers genuine potential during field trips at summits. The scanner is easily operated using an inexpensive, lightweight and rechargeable Sealed Lead Acid (SLA) battery.  A battery with a capacity of nine Amp hours (Ah) is more than adequate for this scanner. A handheld MP3 recorder featuring line-in recording can be connected to Tape Output on the rear of the scanner to permit monophonic recording of reception, including FM broadcasts.

Realistic PRO-2006 supplied antenna © 2014 FM DXing at WordPress

FM broadcast band tuner module

The PRO-2006 incorporates two 280 kHz, two 455 kHz ceramic filters and a 48.5 MHz crystal filter. Wide FM mode is designed for analogue FM and TV audio only.

Realistic PRO-2006 tuner module, rear unit perspective © 2014 FM DXing at WordPress

The PRO-2006 has two 10.7 IF bandpass filters in the FM section (above). These are both marked 10.7A, suggesting a 280 kHz bandwidth. The part number is Murata SFE10.7MA5W-A. The bandwidth of these filters is too wide to discriminate FM stations spaced 100 kHz or 200 kHz apart on the contemporary congested FM band.

PRO-2006 partial schematic © 1990 Tandy Corporation

KA2243N (IC1)  is the IF amplifier/detector Integrated Circuit (IC). The first 280 kHz filter (CF1) leads directly to pin 1. The second 280 kHz filter (CF2) leads to pins 4 and 6. The HA12413 IC may be substituted for the KA2243N.

This tuner module incorporates the IF coils and the Quadrature/detector discriminator coil for both 48.5 MHz (T1, T2) and 10.7 MHz (T3, T4).

FM broadcast band performance

The nominal 30 decibel FM sensitivity ‘design specification’ for the PRO-2006 is 3 microvolts for frequencies from 25 – 520 MHz. The FM broadcast band falls into this segment.

Radios featuring a Si4734 digital AM/FM radio receiver IC, such as those manufactured by Tecsun, offer approximately equal sensitivity as the PRO-2006 scanner in Wide FM mode. It is impossible to make entirely accurate comparisons between the Silabs’ Digital Signal Processing (DSP) based receivers and conventional tuners, since the company use differing units and test conditions to measure sensitivity. However, the nominal 30 decibel FM sensitivity ‘design specification’ (below) from Tecsun, applicable for radios such as the PL-300WT & PL-606) is better than 3 microvolts for frequencies from 64 – 108MHz.

Tecsun specifications © 2014 FM DXing at WordPress

How to access the tuner module

Unscrew the two, top positioned screws on the rear of the scanner. Remove the top plastic cover top to expose the ‘linear printed circuit board’, PC1. Remove the metal cover of the tuner module (below), which is located second from the right.

PRO-2006 interior modules © 1990 Tandy Corporation

Replacing wide 280 kHz filters in the PRO-2006, PRO-2005, PRO-2004, PRO-2035 or PRO-2042 scanners is likely to be as simple as the modification to the Philips FM1216-based tuner module, used in television tuners such as the Winfast TV2000XP. An excellent resource for this modification is GBPPR Projects.

Realistic PRO-2006 frequency display © 2014 FM DXing at WordPress

Mating the PRO-2006 with a Software Defined Radio (SDR)

After filter replacement, tapping the 10.7 MHz IF (both mods are described at GBPPR Projects) may enable the 10.7 MHz output from the scanner to be manipulated with DSP functionality in an SDR. Unfortunately, readers wishing to do so are ‘on their own’ because the writer does not own a compatible SDR (such as the SDR-IQ). It may be instructive to watch the video Gough Lui made. He taps the 10.7 MHz IF of the PRO-2021 scanner into the Winradio Excalibur SDR. Peter employs the same principle in his video.

A more inexpensive alternative may be to use a High frequency (HF) upconverter in combination with a cheap RTL-SDR receiver. Such upconverters are available for under $50. Unlike the cheap RTL-SDR receiver itself, an upconverter will tune into the 10.7 MHz output frequency from the scanner. There are side effects in this approach, which potentially include a 10 decibel loss and the limiting dynamic range of the RTL-SDR receivers.

Pairing the scanner with an SDR offers hobbyists the opportunity to extract the maximum potential audio quality out of FM broadcasts or International Radio and Television Organisation (OIRT) broadcasts on 66-74 MHz still on-air in Eastern Europe.

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PRO-2006 photographs may be freely used for non-commercial activity, provided attribution is given. Should readers choose to use those photos elsewhere, please link back to this page or attribute this blog as the copyright holder. Please click on the photos for higher resolution shots (2048 x 1536 pixels).

Eighties Retro Radio

Rewind time back to 1988 and an ‘el cheapo’ FM stereo tuner kit looked like this! The three modules pictured below consisted of an:

  • FM tuner (steel shielded front end),
  • Intermediate Frequency/detector (IF) &
  • FM stereo decoder.

The three modules connect together with 28 inexpensive supporting components to comprise a fully functioning FM/AM tuner with a basic signal strength meter, LED stereo indicator & coaxial cable antenna input.

Tuner module © 2014 FM DXing at WordPress

Module for IF & Detector © 2014 FM DXing at WordPress

Module for Stereo Decoder © 2014 FM DXing at WordPress

The tuner featured analogue tuning with switchable Automatic Frequency Control (AFC) feature. AFC is rarely mentioned these days. In a nutshell, AFC circuitry automatically locks to the tuned frequency so as to facilitate ‘drift free’ reception of the desired FM broadcast; automatic correction is applied when the dial is ‘off-tuned’. In a congested FM band, the function is best switched off, otherwise that weak signal might be hard to find.

Contents of Electronics Australia magazine © 1988 Federal PublishingCover of Electronics Australia magazine © 1988 Federal Publishing

The above tuner was featured as a Do It Yourself (DIY) kit in the now defunct Electronics Australia magazine (above) from April 1988. Hand written & printed schematic diagrams and modules (above) were found in buried in an old set of drawers.

The schematics for each module appear below:

FM tuner schematic © 2014 FM DXing at WordPress

FM IF & detector schematic © 2014 FM DXing at WordPress

Stereo decoder schematic © 2014 FM DXing at WordPress

Further reading

1974 MPX-stereo decoder with TCA290A

TCA420a datasheet

AFC Definition

AFC Explained

What is AFC?

Why choose plain FM over FM AFC?