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Frequently Asked Questions (FAQ)


  1. Can you provide me with a manual, schematic diagram or spare components? How do I program my device? Do you have other modifications? How can I repair my equipment? Do you have a Declaration of Conformity? Do you have any other information on my device? Do you sell equipment?

    Almost all equipment on this site belongs to other people. I only make a discriminator output on it. I don't have any manuals or schematic diagrams, nor components, nor equipment for sale. Apart from the modification shown on this site, I don't have specific details about your device. Sorry, but I can't help you.

  2. Do you have a modification to unblock the cellular band on my scanner? If I use a discriminator output, can I monitor cellular phones?

    No, I don't have modifications for that. No, you can't use a discriminator output to listen to cellular phones.

  3. Do you have frequencies for my area?

    I can't help you with that. This site is about discriminator outputs and paging monitoring. It is not the intention of this site to maintain a worldwide frequency database.


  1. Can you help me with the settings of PDW? How do I get PDW working on my PC?

    I lack the time to give individual support with PDW. Please check the manual or refer to the Forum on this site.

Discriminator Outputs

  1. My device is not listed. Isn't it possible to equip it with a discriminator output?

    (Almost) any narrowband FM receiver can be equipped with a discriminator output: every FM receiver contains a discriminator. If your device is not in the menu, it simply didn't pass my workbench yet.

  2. How do I add a discriminator output when my device isn't listed?

    Take a look at this overview to see if your receiver is listed in table 1. If not, check whether your scanner contains a discriminator IC that is mentioned in table 2. If you found the IC, you can get some inspiration from table 3 by checking equipment with the same discriminator IC.

    You can always find the right spot with an oscilloscope.

  3. Do any receivers exist with a factory fitted discriminator output?

    Only a few receivers have a standard discriminator output. They are listed in this overview.

  4. I have an amateur radio transceiver. How do I equip it with a discriminator output?

    Many amateur radio sets have a 9600 bit/s packet radio output. You can use this in stead of a discriminator output.

    Amateur radio equipment is often built very compactly, so you'll lack the space to put an additional chassis terminal in the transceiver. Why not consider buying a cheap (vintage) second hand scanner for digital modes monitoring.

  5. Can I still use my scanner after the modification?

    Yes, your scanner keeps all its normal functions. Adding a discrimator output does not affect your scanner, provided that it is done properly.

  6. What's the function of the resistor?

    Connecting or disconnecting an interface to the discriminator output might cause a short-circuit. The limiting resistor prevents the discriminator IC from being loaded or damaged. Further to that, it prevents your PC's microphone or line input from being overloaded.

  7. What's the value of this resistor for my scanner?

    The value is not critical. I usually use 10 kilo-ohm. The miniature resistors on my site are 1/8 W, the normal size resistors 1/4 W.

  8. What's the function of the capacitor?

    With some discriminator ICs, especially the MC3361, some IF signal 'leaks' into the discriminator output. You can see the effect on the oscilloscope pictures. The resistor and capacitor form a simple filter that attenuates the 455 kHz IF signal, while leaving the digital baseband signal intact. Some practical combinations are:
    • 5.6 k with 4.7 nF
    • 10 or 12 k with 2.2 nF
    • 15 k with 1.5 nF

    A ceramic capacitor for 50 V or higher is fine.

  9. Can I order the components for a discriminator output?

    If you order an interface or circuit board, the components for a discriminator output can be included at cost. In that case, please use the contact form so that I can offer you a combined price. Otherwise, you can buy them from an (online) electronics shop.

  10. I use an SDR stick, but I don't get any or garbled text

    Double check the SDR settings (frequency, gain). The recording settings of your soundcard are critical. There is no guarantee for succes. For a 100% no-fuss result you should consider using a cheap second hand scanner in combination with one of the interfaces on this site.

  11. I made a discriminator output, connected it to the soundcard, but I don't get any text

    Double check your connections. If you connect an earphone to the discriminator output, in a quiet room you should be able to hear a faint sound. You could also try to monitor the line or microphone input with a Windows oscilloscope.

    The settings of your soundcard are critical. There is no guarantee for succes. For a 100% no-fuss result you should consider using the discriminator output in combination with one of the interfaces on this site.

  12. When I connect the discriminator output to my laptop's microphone input, the scanner's audio drops

    Probably the microphone input carries a DC voltage. This is used to provide power to a microphone. In combination with some scanners, this may be an issue.

    The remedy is to put a 10 uF, 25 V electrolytical DC decoupling capacitor in series with the discriminator output. An example can be found here. daarvan.

    If you use an interface from this site, this capacitor is not necessary: it's built in in all interfaces.

  13. Can I connect the discriminator output to an AIS-enabled chart plotter?

    A chart plotter expects an NMEA signal. A discriminator output carries the raw AIS signal. This has to be processed to convert it to the NMEA protocol and signal levels. Option 1 describes how to do this.

  14. Can I use the discriminator output for ACARS?

    ACARS is an AM signal. A discriminator output is made on the FM part of your receiver.

    ACARS uses an 1800 Hz tone, which is phase modulated with a shift of 1200 Hz and 2400 bit/s (MSK - minimum shift keying). This MSK modulated audio signal is then transmitted in AM. The audio signal fits perfectly in the audio spectrum of an AM receiver (300-3000 Hz). Through this indirect modulation method, an AM detector output is not necessary.

    In most cases, you can use the earphone output of your receiver for ACARS.

  15. Can I use the discriminator output for ADS-B?

    ADS-B (Mode S with extended squitter) is transmitted on 1090 MHz. Most scanners can't receive this frequency. Apart from that, the bandwidth of an ADS-B signal is about 2 MHz. A scanner has a receiver bandwidth of about 25 kHz, and is not suited to receive these broadband signals.


  1. Why would I need an interface?

    The two main reasons to use an interface are:
    - It gives you more reliable decoding than using the soundcard
    - You don't have to find the right soundcard levels, which can be a tedious process

  2. What is the difference between an RS232 interface, a USB interface, a 2 level slicer and a 4-level FSK interface?

    With an RS232 interface, USB interface or a 2 level interface you can monitor 2 level signals (POCSAG; 2-level FLEX, Mobitex)

    With a 4 level interface you can monitor both 2 and 4 level signals (POCSAG; 2 and 4 level FLEX; ERMES).

  3. Can I connect the interface to my scanner's earphone output?

    For error free monitoring of paging signals, you need a discriminator output in combination with an interface. Using an interface in combination with an earphone output is a waste of the investment. In that case, you're probably better off using the earphone output in combination with your PC's soundcard. A 4 level interface almost certainly won't work with an earphone output.

  4. Can I use a USB to serial converter?

    An RS232 interface has been developed that enables the use of a USB to serial converter. The interface has been available from 2010 to 2018. In October 2014, based on the RS232 interface a USB interface has been developed that can be connected directly to a USB port.

    To use a 2- or 4 level interface, you need a 'real' serial port.

  5. Can I use the interface for AIS?

    To monitor AIS, you need to connect your receiver's discriminator output to your PC's soundcard using an audio cable. With Shipplotter you can then monitor AIS. The interfaces are meant for decoding paging and will not work with AIS.

  6. Can you send me an interface?

    You can go to the Order Information page to find price information and order directly using the 'Buy Now' buttons.

    I accept PayPal, Credit Card, bank transfer and cash. I ship worldwide. However, you may have to pay customs duty and tax if you live outside the European Union.

    Feel free to contact me for further ordering information.

  7. Can I order a printed circuit board? An unassembled kit with components?

    For the USB interface, a professionally manufactured circuit board is available, together with a programmed and tested PIC16F628 microprocessor.

    Only common components are used. They can be obtained easily from an (online) electronic components supplier

  8. Can you send me the hex code for the 16F628 microprocessor?

    Developing the software took quite some effort. That's the reason for not making the source code or hex file available for now. For the USB interface, a professionally manufactured circuit board is available, together with a programmed and tested PIC16F628 microprocessor.

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