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Flex 6600 and RapidM RM2

Glenn Depp
Glenn Depp Member ✭✭

I have been working on my new RapidM RM2 modem and connecting to the Flex6600. I so far with help have been able to get TX and RX audio lines figured out in the PINs for the connector. My current issue is the PTT pin. The pinout of the Accessory connector on the Flex is very lacking, or so it seems to me. I have a pinout diagram from RapidM that is fairly complete, however, Not sure exactly where these should be gong in the Flex pin out. Is there an actual pinout diagram available or no.

My other issue is the audio that is piped into the accessory pinout seems inappropriate. The audio for the external modem is the speaker output, not a gneric set level output. We have to have all levels on the slice to be used maxed out to get appropriate audio levels into the modem. Thus requiring external radio speakers to be manually lowered so as to not have the loudest possible audio being heard by our ears. Seems counter productive, and makes use of the maestro rather useless without dedicated speaker out with level control coming form the radio direct and not on the front maestro speakers.

Does anyone have any help with the pin out on the Flex 6600 for the RapidM RM2. I do have the RapidM RM2 pin out sheet available.


  • Arizona Mike
    Arizona Mike Member ✭✭

    I am interested to hear how you make out with this install. If successful, I may elect to purchase an RM2. Please keep us updated.


  • Glenn Depp
    Glenn Depp Member ✭✭

    Who all is using a Flex and RapidM RM2? I am still having an issue with the PTT connection. I can receive just fine. When I try and transmit everything looks like it should be working, however the Flex does not transmit. It works ONLY if I make it transmit by pressing on my PTT foot pedal for my microphone.

    My Flex setup:

    software version is v3.3.32

    I have tried both DIGU and USB

    I have tried both AF input sources as ACC and BAL (mic)

    I have the +ACC on

    DataPoint v 1.1.6 connected to RM via hardware comport.

    CP connected to DataPoint (DP) via DPs virtual comport.

    --I do not seem to have an issue with the software trying to transmit, receives fine, same issues when using the Maestro, no difference in issue.


    Cable supplied from NVIS Communications, non-terminated.

    My wiring is below; All wires come from the ENDpoint 4 cable.

    DB25F--> COLOR <--DB15

    1 --- BLACK (GND) --- 10 OR 5

    2 --- RED (AUD1_RX+)---- 2

    3 --- ORANGE (AUD1_TX+) --- 1

    5 --- GREEN (AUD_KEY1_OC) --- 11 have also tried GRAY

    14 -- BLUE (AUD1_RX-) --- 7

    15 -- PURPLE (AUD1_TX-) --- 6

    18 -- GRAY (AUD_PTT_IN1) --- 11 have also tried GREEN


  • k7rfh.rich
    k7rfh.rich Member ✭✭

    I am also interested in this as well. I have a 6400 and will be getting a RM2 modem shortly.


  • Glenn Depp
    Glenn Depp Member ✭✭
    edited August 2022

    I now have it working. RM2 Wiring into the Flex 6600 is:

    PIN 1 - ORANGE (AUD1_TX+)

    PIN 2 - RED (AUD1_RX+)

    PIN 6 - PURPLE (AUD1_TX-)

    PIN 7 - BLUE (AUD1_RX-)

    PIN 5 - BLACK (GND)

    PIN 11 - GRAY (AUD_PTT_IN1)

    PIN 14 - GREEN (AUD_KEY1_OC)


  • Glenn Depp
    Glenn Depp Member ✭✭

    Now that I am able to transmit properly I am seeing issues with how the FLEX 6600 utilizes this accessory port. I have heard this before from others, however, I now see it as well.

    1. The audio being sent out of the flex for use with external 3rd party hardware is using the same audio I listen to with my powered speakers. This means that the audio drive levels for my speaker in the SMART SDR software ALSO controls how much audio is sent to my third party device. This means I have to have the audio set to MAX in the top right speaker control bar of Smart SDR, Max to near max in the slice audio control, the AF gain needs to be set near max to have the required audio level drive high enough for the 3rd party hardware device to have the audio drive levels needed.
    2. Another issue is the mute function for each individual slice you are using on the accessory port ALSO mutes audio going to the device. So you have to have the slices un-muted. This requires using the external speakers to control all audio for your listening rather than simply muting the slice or what have you.
    3. Another issue is your microphone connected at-least to the BAL mic input is also HOT every-time you transmit via modem on the accessory input. This means you cannot have background noise or it is transmitted along with the data signal. I have not tried the MIC input as of yet and do not know if it is also effected or not.
    4. If the DAX is turned OFF then the microphone is also hot continuously, just not transmitted unless the modem keys radio. If the DAX is selected then the BAL MIC is not hot. Not sure if this occurs for everyone or my setup.
    5. This may be non-related and simply a local issue, I know of one other currently who is experiencing this, When I transmit my speakers have interference during transmission. I have not yet put any ferrites on any cables and my modem is sitting directly on top of the radio.

    If I find any other issues I will post.

    I will be looking at purchasing a DR-7800 P4dragon PACTOR 4 Modem next year and hoping to find a way to split the accessory connector. I would like to find a switch to move back and forth between multiple modem types. I am thinking a standard monitor selector with modifications would likely work.

  • Alan
    Alan Member ✭✭✭✭


    I am not familiar with the DR-7800, but am experienced in Flex interfacing.

    I understand you observation when using the Flex accessary connection for AF in and Out.

    Another approach would be to use either of the DAX applications. There are Windows, Mac and Linux versions available.

    Use TX DAX to send audio (TX Streaming) to the Flex AF in, and use RX DAX to receive audio from any of the slices you have open.

    This now makes the PC that is running DAX, the audio in and audio out source. Make your wire connection to the DR-7800 to/from your PC. You will no longer see the issues you describe above. AF in and out levels are adjusted on the PC, not on Smart SDR.

    Alan. WA9WUD

  • Glenn Depp
    Glenn Depp Member ✭✭
    edited August 2022


    DAX is not an option with 3rd party Hardware devices.

    What I was refering to is the Accessory port on the back of the radio. There is no internal sound looping for external hardware devices.



  • Alan
    Alan Member ✭✭✭✭

    I understand.

    Use DAX to make your PC the sound device.

    Hard wire the PC sound in/out to your device.


  • Arizona Mike
    Arizona Mike Member ✭✭

    Glenn wrote:

    "Another issue is your microphone connected at-least to the BAL mic input is also HOT every-time you transmit via modem on the accessory input. This means you cannot have background noise or it is transmitted along with the data signal. I have not tried the MIC input as of yet and do not know if it is also effected or not."


    I find that adjusting the DEXP can filter out much of the background noise if needed. Not sure how this will work with the RM-2 situation as I am still afraid to spend that much vig on a device that may not completely interface cleanly.


  • Mark NS9N
    Mark NS9N Member ✭✭

    Hi Glenn,

    For those of us who are interested in leaning everything we can about Ham Radio, and may not understand what you are trying to accomplish, can you give us a breif explanation of what you will be able to do with your RapidM RM2? I have a fully remote 6600 station using a Raspberry Pi remote access control I built and then run the standard Flex SW for both remote PC or the Apple App. But it sounds like you are trying to accomplish more?

    Thanks for a learning experience.

  • Glenn Depp
    Glenn Depp Member ✭✭

    So the RM2 is not going to fulfill much in amateur radio. In the HF spectrum only 60 meters frequencies are authorized for use of the data modes this modem utilizes. Outside of amateur radio these modes are much more common, many utilize software versions of the modem and a sound card interface. The RM2 is a hardware version, there is no direct access to a sound card interface, it is a direct wire via 15 pin connection on the accessory port. The bad part is the audio gong to this port is derived from the audio out to powered speakers and not a clean audio with no modification such as the software EQ when using USB therefore DIGU is the preferred method, which then also limits the ability to use the EQ for transmitted voice audio to increase quality. I have found the RM2 rmuch better than our current version software modem which does use the DAX. DAX has zero effect and is not usable in anyway with the hardware modems. Also any filtering can also effect the received signal and cause processing issues so no filtering is always best for digital.

    Other than how the audio is supplied this modem is working great. Once again only useful for those not operating only in the amateur radio bands.

  • Arizona Mike
    Arizona Mike Member ✭✭

    If and when there is a solution to the audio issue, I will order a Rapid M - RM2 modem. I am itching to dump the software DMT modem and all it's issues.

  • Glenn Depp
    Glenn Depp Member ✭✭

    Arizona Mike,

    It really isnt bad. I so far love this modem. Works very well. The only thing is you MUST have the main computer audio, slice audio level and the slice rf drive or af drive also set to 95 to get the required audio levels to the modem. Other wise it is great. You also need external speakers connected to radio and utilize its speaker levels for you to listen to.

    I recommend it at this point. I would like to see some changes on flex's side to the audio issue, but still very good.

  • John WA7UAR
    John WA7UAR Member ✭✭✭

    @Glenn Depp - do you think it would be possible some how to set the RM2 up locally to a Flex but control it remotely? Possibly using TeamViewer on a local PC connected to the physical audio ports on the Flex?

  • Arizona Mike
    Arizona Mike Member ✭✭

    What I was thinking about is this;

    A simple multi channel software or studio mixer routing Audio from one of the unused channels with the proper levels into the RM2 might work. This would allow the desktop speaker or headphones to be adjusted separately from the RM2.

    I currently do this with my studio mic. The mic is plugged into a preamp which is then routed for use v=by Zoom, etc. I activate Output Channel 5 and use a balanced cable into the Flex 6600 Line In. Allows gain staging from the preamp, and from the mixer fader as well as within SSDR.

  • Glenn Depp
    Glenn Depp Member ✭✭


    I would only assume you would have to be remoted in via something like team-viewer to utilize the RapidM modem as it is controlled directly from the computer it is physically attached to and does not use any virtual connections other than to the data source.

  • Arizona Mike
    Arizona Mike Member ✭✭

    Just wondering if the RM2 is still working well with your Flex.

  • Glenn Depp
    Glenn Depp Member ✭✭

    Yes. I love it. Way better than any other software M110 Modem I have used. Which has been the only 2 I know of that exists.

  • Glenn,

    I have a 6400 & RM2 unterminated cable; I followed your pin outs and initially it worked but now NOT. The radio will show TX (red light on) but the watt shows no RX going out. Audio setting i suspect; RapidM says it requires 600 ohm balanced.
    Any suggestions?


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