• Asymod ™ and the Galaxy DX-939 Hi-Fi Asymmerical AM Transceiver

    Please enter carrier level required
    Please enter the modulation (%) desired or maximum PEP (W) allowed


    Be sure to see the Stryker SR-955HPC in Hi-Fi action with the NEW Asymod IIIs in this highly requested real-human-voice demo and the Asymod III with the Cobra 29 LX BT & Galaxy DX-939 real time demos.

    Got questions? Visit the new Asymod related FAQs and get answers to the most frequently asked questions and lots of valuable information related to Hi-Fi communications.

    Go Pro mobile or base with this Galaxy DX-939 Plug-n-Play Hi-Fi transceiver. Transmit and receive in Hi-Fi audio with this all in one unit with the NEW Asymod IIIs.

    Now you can make your mobile or base station sound like you always wanted it to at an affordable price. If you are tired of spending on expensive gear or trying different combinations and still don't have the Hi-Fi audio you want for your radio station setup, this is the way to go. With this setup you will save in time to come as there will never be the need to upgrade again.

    The receiver section has been upgraded to a Hi-Fi receiver. A 6 kHz bandwidth / 455 kHz IF AM filter has been installed and the detector, audio control and amplifier stages have been upgraded to provide the necessary bandwidth to enjoy and hear the audio from other AM Hi-Fi stations with clarity without the need to spend hundreds of dollars in external Hi-Fi receivers. (Good quality headphones or external speaker is recommended for best results).

    Simplify your setup and get the pro audio you want with this all in one, neatly designed setup. Simply connect the output of your audio process gear to the rear panel Line-In connector or the hand microphone to the front panel Mic-In connector and go. There is no need for internal adjustments. Truly Plug-n-Play.

    In addition to the stock accesories and functions, this unit includes:

    • 6 kHz bandwidth / 455 kHz IF receive filter and Hi-Fi upgraded audio amplifier section.
    • Front panel microphone operation with active Mic Gain. No internal audio input level adjustments needed for neither inputs.
    • Front panel Mic In connector is interruptible by rear ¼" phono connector.
    • Unbalanced front panel Mic In and rear panel Line In inputs. Front panel Mic In accepts microphone level inputs and is adjustable via the Mic Gain front panel control. Rear 1/4" phono connector accepts line level inputs up to .5 volts P-P; .25 volts PK or -2dBm.
    • Mic Gain control is active when using the front panel Mic In microphone connector input via a Hi-Fi pre-amp to Asymod III.
    • Asymod III internal input gain levels do not need adjustments when switching from Line In. (1/4" phono connector at rear) to Mic In (front panel mic connector).

    PTT Connections

    The PTT connector in the rear has been added because most Hi-Fi stations use studio type microphones which do not have a PTT.

    PTT connections are available at the front panel 4 pin microphone connector and at rear panel PTT connector.

    When using the rear Line-In audio input, either the optional mouse PTT or a foot pedal connected to the rear panel PTT connector or a hand microphone connected to the front panel 4 pin microphone connector can be used as a PTT.

    When using a hand mic connected to the front 4 pin microphone connector, the rear panel ¼" TS Line-In connector must be unplugged. While using the hand microphone use it's own PTT.

    If a microphone other than a hand mic that does not have its own PTT is connected to the front microphone 4 pin connector, either a mouse or foot pedal connected to the rear panel PTT connector can be used as PTT.

    Audio Processing

    Setting up your Asymod transceiver is easy, you can choose from simple to more complete and elaborate setups as seen bellow. For those who prefer standalone units instead of computer based audio processing such as Pro Tools, below are two possible setup configurations using the Behringer DEQ2496 processor. Additional information regarding the AM Hi-Fi audio process visit the NU9N page at the following link: http://www.nu9n.com/am.html

    Bellow is a simple Pro Tools Hi-Fi setup. A more complete Pro Tools setup can be put together in the same manner as the above complete Hi-Fi setup.

    The rear Line-In should be used for Hi-Fi applications as it is a direct feed to the Asymod IIIs. The front mic jack audio passes through the transceivers mic preamp, and although the transceivers mic preamp has been upgraded to pass wideband audio, it is best to use the rear panel ¼" TS Line-In connector. In the case where audio processing is not available, and as a last resort, a hand microphone can be used. A dynamic microphone with tone controls, such as the Astatic 575-M6, RF Limited CR577 or similar is recommended, but this somewhat defeats the purpose of the Hi-Fi functionality of the Asymod IIIs. KEEP IN MIND PROCESSED AUDIO GIVES YOU THE PUNCH, DEPTH, DYNAMICS AND BANDWIDTH THAT MAKES IT STAND OUT FROM THE REST.

    With this setup, there is no need for messy external power supplies, audio or power wires prone to RF interference, and best of all, all your contacts will want to sound like you. 

    If youre tired of spending on expensive gear or trying different combinations and still don't have the Hi-Fi audio you want for your radio station setup, then check out the BLUthunder Technologies' Asymod III Asymmetrical Hi-Fi AM Modulator at work in this video and see for yourself how this affordable setup sounds just as good or better than commercial AM broadcast stations. Dare to try the Asymod IIIs? 

    The Asymod IIIs is installed and calibrated at requested specifications. 

    This unit is usually set at 1 watt carrier with peaks of 12+ watts PEP / ~250 % modulation. Other settings may be requested.

    Carrier to PEP ratios:

    100 % modulation is 4X the carrier in Peak Envelope Power (4:1) 

    150 % modulation is 6X the carrier in Peak Envelope Power (6:1) 

    200% modulation is 8X the carrier in Peak Envelope Power (8:1) 

    250% modulation is 11X the carrier in Peak Envelope Power (11:1)

    300 % modulation is 15X the carrier in Peak Envelope Power (15:1)

    Available preselected settings:

    1 Watt carrier / Adjustable from 100% to 350% Modulation

    1.75 Watt carrier / Adjustable from 100% to 300% Modulation

    2 Watt carrier / Adjustable from 100% to 250% Modulation

    3 Watt carrier / Adjustable from 100% to 200% Modulation

    4 Watt carrier / Adjustable from 100% to 150% Modulation

    The Asymod IIIs comes with downloadable:

    Description Manual

    Installation Manual

    Operation& Troubleshooting Guide

    Downloadable PC Oscilloscope Manual (For those who don't have oscilloscopes)


    The Asymod IIIs compact design makes it ideal for mobile and base operation and allows for internal mounting and simple installation in the transceiver with the included hardware and only requires a 12 Volt supply. The Asymod IIIs expands the transmitter’s audio bandwidth from the stock 3 kHz to well over 10 kHz. On board preset active and passive low pass filters can be set to 6, 8 or 10 kHz roll offs. This allows for the entire selected audio bandwidth to be transmitted.

    The asymmetrical functionality controls the audio loudness level and provides for amplitudes in excess of +300% modulation while not exceeding the negative peaks at -100% without the use of negative peak limiting or clipping methods which produce squaring of the modulation envelope and provides for increased spectral density. The Asymod IIIs is compatible with most transceivers and it is fully adjustable via the onboard controls and accepts microphone and line level inputs. It offers the flexibility to use a stock hand mic to a high end processing audio chain using a broadcast microphone. This unit will work with all High Level Modulation transceivers by direct coupling to the driver and final’s collectors via the existing transceiver's onboard RF chokes without the need for a heavy, costly and large modulation transformer.

    The Asymod IIIs produces modulation levels well above the norm and broadcast levels without distortion, allowing for your station to sound loud and clean. With the Asymod IIIs connected to your audio processing chain you will sound just as or better than commercial broadcast stations.

    To achieve optimum results and to make the most of the Asymod IIIs, adequate audio processing catered to emphasize on your natural voice is necessary.


    Read through all related documents, including the Asymod FAQs and manuals to see the requirements for an effective Hi-Fi setup before committing to purchase. All sales are final and there are no returns. If the unit breaks, please send it back for repair. All repairs are free within the first two months after the sale.

    The transceiver/radio is only the exciter and should not be expected to generate high levels of RF power, it should be expected, however, to generate a clean, perfectly modulated wide-band Hi-Fi audio RF signal well within the limits of the headroom available without pinching or clipping at the crest or troughs of the modulation envelope which can be later amplified with a class AB, RF power amplifier and is best heard or monitored on a good quality receiver equipped with a 6 kHz AM wideband filter and monitored on an oscilloscope.  

    The Asymod is not an audio processor, but it does allow for full bandwidth control with the use of Pro Tools, a combination of rack gear, or a broadcast multi band compressor / limiter.  

    Audio processing and a high quality microphone is necessary for optimum performance. 

    Audio processing for mobile or base operation is possible with the use of the iRig PRE or iRig PRO interface using the companion IK Multimedia's VocalLive Vocal Processor app (not the free version) on your iOS device. 

    Audio processing for base operation is possible with the use of rack audio processing gear or computer based processing such as Pro Tools for PC or Mac along with its companion interface such as the Mbox 2 Mini or newer. Pro Tools is the best choice and is highly recommended. Pro Tools sessions are free and available for download. 

    The Asymod IIIs is NOT designed to give transceivers more RF power, more swing, or loud distorted modulation. It is however, to be used in conjunction with a properly set audio processing scheme to produce the loudness, punch, depth, and audio bandwidth with enhanced performance in tone, smoothness and dynamic range of a broadcast quality transmission which is what makes it stand out from the rest.


    Features of the Asymod IIIs 

    Recently added features to the new and improved design of the Asymod IIIs include on board passive and active selectable low pass filters which provide preset roll off points, remote control operation via the on board Solid State switch which provides mode switching for ease of installation in multimode transceivers. Enhanced RF suppression circuits have been added and board layout design has been optimized to eliminate and avoid any stray running currents due to RF interference. Single supply operation provides for a very low noise and quieter operation. New onboard unbalanced audio preamplifier with independent input and output to be used in any installation where audio levels need to be matched as it applies to the SSB Balanced Modulator input levels for eSSB operation or as a microphone preamp. 

    The Asymod IIIs compact design allows for easy mounting inside your transceiver and offers all the combined features comparable to high end, very expensive broadcast gear and other available Hi-Fi mods upwards of $1000 and makes for the most important part of a Hi-Fi AM station. Hi-Fi Audio is very thought after by many radio operators nowadays and the Asymod IIIs delivers all the necessary functionality and stands as the backbone of the station.

    • Mobile or base operation, ease of use and simple installation; only a 12 Volt, 5 Amp power supply is required. 
    • Rugged design built on a tough PCB to provide years of continuous use.
    • Audio gain control allowing for proper drive from the microphone and line level input. 
    • Modulation Level control allows for final audio control and is set in combination with the Carrier and Asymmetry controls to achieve the level on modulation desired.
    • Carrier controls sets the reference carrier level (dead key) to set the modulation and asymmetry levels. 
    • The Asymmetry control maintains the negative peaks at -100% modulation while allowing for positive peaks of excess of 300% without pinching or clipping. 
    • Preamplifier gain control to allow matching of audio levels. 
    • Remote ON/OFF control.
    • Power status LEDs for the 12V and onboard 24V supply. 
    • Input voltage polarity protected. 
    • Modulation peak indicator. 
    • Convenient mount holes. 
    • Heavy duty screw terminal block connectors for the line in, power in, modulator output, pre-in and pre-out connections. 
    • TO-220 and TO-247 onboard compatibility for mounting single or dual modulating stage transistors.

    Asymod IIIs absolute maximum ratings:

    Audio input:

    +4 dBu, 1.74 VPK  or  1.23 VRMS

    Power supply:

    +15 volt supply @ 5A

     Remote control sensitivity:

    +8V ~ +12 V

    Asymod IIIs Specifications:

    Audio Input Range: Audio input: -30 dBu to +4 dBu

    Frequency response:
    Input: 20 Hz – 11 kHz.       Expandable to 20 kHz.
    Output: 20 Hz – 11 kHz.    Expandable to 20 kHz.

     Total System Distortion (@ 300% modulation):
    <0.01% THD 20 Hz – 1 kHz
    <0.02% THD 1 kHz – 5 kHz
    <0.03% THD 5 kHz – 14 kHz
    <0.05% THD 14 kHz – 24 kHz

    Input & Output Passive Low Pass Filter:
    Selectable: 5 kHz, 8 kHz, 11 kHz or 20 kHz

    Preamplifier Active Low Pass Filter:
    Selectable: 8 kHz, 16 kHz

    Transceiver Specifications:

    AM TX:

    Carrier: 1 - 4 watts

    Peak Envelope Power: ~20 watts

    Modulation: 100% – 350%

    TX Bandwidth: Up to 10+ kHz (dependent on audio process roll-off)


    AM RX:

    Bandwidth: +/- 7.5 kHz

    Att Band Width: +/- 15 kHz

    Stop Band Att 455/ +/- 100 kHz: 40 dB

    Audio Amplifier Frequency Response: 15+ kHz

    Please Read Before Buying

    Please do all research and ask all questions before buying.

    Take a look at the pictures and the oscilloscope captures for actual results.

    Please allow 4 to 7 weekdays after the order is placed to assemble the unit. Unit ships out within 4 to 5 business days of cleared payment if unit is ready otherwise as soon as the unit is ready.

    Have questions? Contact Asymod support: asyadvice@gmail.com