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CW RF Drop Out



  • Roger G3LDI
    Roger G3LDI Member ✭✭

    All comments noted. As for Len KD0RC saying he would try to understand what leads up to this fault, **** chance! It's either there or it's not. Intermittent problems are the worst to track down and I don't see how this can be. The only way that might be fruitful is for the software authors to look at the CW module in version 2.4.10 because that is the ONLY one that is free from this fault. If it is a subroutine or similar, then place that in the latest software, but it probably is not that simple.

    I have three videos here of the problem. They are well defined, but long. They are impossible to send as attachments. If anybody would like to see them, please email me [email protected] and I will let you know how you can download them. I shall be using WETRANSFER. I have to upload them and you have to download them. I shall email Ken Wells as I think he might like to see them.

    73 de Roger, G3LDI

  • Martin_G4ENZ
    Martin_G4ENZ Member ✭✭

    I note the topic here is CW drop out but I would like to suggest a possible link to another issue that I have long seen discussed in the community and that is VOX dropout. The release notes for 3.4.21 suggest that a VOX issue has been fixed.

    VOX Fixes: Fixed intermittent VOX hanging in RX issue (SMART-8919, SMART-9154)

    But I am still seeing it in 3.4.21. This morning on our daily 10m SSB net I tentatively starting using Vox again. I ran the excellent Flex Meter to monitor output power and what I see sounds very similar to what is being reported with CW drop outs.

    You can see the regular excursions to 0W as I pause and allow the receiver to come in. You can see the unwanted drop out in output power at 09:04:02 which is only reset after the next time the radio goes to receive at 09:04:05. I would be interested if someone could put up a similar picture of the CW drop out. I am noticing that with the Vox issue, the power change is a fade rather than a cut and it appears to fall to a very low power level rather than zero.

  • Mal G3PDH
    Mal G3PDH Member ✭✭

    Hi Martin

    Thanks for your input. I have never really used VOX in anger on the Flex so unable to confirm about experiencing that. However I had noted that intermittent VOX reports had been made and that the latest release had supposedly addressed that issue so I was interested to see if those changes had impacted the CW RF drop out problem. I am not familiar with the internal relationships between these things but there could be a connection. I have also just discovered that when the CW RF drop out happens the PTT line out to my linear amp fails which could also be part of the problem.

    We are working with Ken Wells on behalf of Flex to carry out more testing in order to narrow this very random intermittent fault down. It could be useful to know if the PTT line fails on the VOX problem too. The CW RF drop out is definitely an immediate drop to zero not a fade. I do have a copy of Flex Meter on my PC and will try to incorporate in the testing that I plan to carry out tomorrow.

    73 Mal G3PDH

  • K0FG_Fred
    K0FG_Fred Member ✭✭

    My problem sounds somewhat different than the ones here. I have been playing in the ARRL DX CW contest. Made 11 contacts and finally gave up because the keying is so erratic. I had to repeat call or exchange at least on half the 11 contacts I just made. But my problem is that the radio just does not key. My callsign ends in FG and several times the macro from WriteLog sent AE O , or TE W. And the same thing happens when using paddles or straight keys so it's not the Writelog program.

    But others have reported no problems when using macros. Over the past year, since I bought my first Flex I have reported this problem several times. I have a paddle connected to the key jack in the back of the 6400M and I have 3 straight keys connected to the DB9 acc jack. I have problems with all 4 keys, and several other keys also. When I send a string of dits and dahs sometimes a character is not seen by the radio. For example if I send an H then one or more of those dits just does not key the radio, it might come out as e i or maybe s or such cuz one or more of the key presses is not seen by the radio. Tried sending at 5 wpm so I can tell exactly which dit did not key the radio. Tried sending at 15, 20, 30 wpm with the same results but it is harder to recognize when the failure happens when using higher speeds. When I say the radio is not keyed I mean there is no side tone, no RF output, no lighting of the MOX button, sometimes the key input is just not seen by the radio.

    I finally gave up on the CW contest cuz I was making a fool of myself when the macro, or the paddle, could not send my callsign correctly. Several times the k0fg was replied with k0teo or k0fw or such, and yes that is what my radio sent.


    ver 3.3.33

    running speeds from 5 to 30wpm

    running 15-100 watts, with and without KPA500 amp

    using several different paddles, bugs, cooties and straight keys

    never tried CWX

    TX delay varied from small to large

    running iambic B with paddles and breakin with the straight keys.

    plugged a straight key into the key jack and turned off iambic, same problem

    Fred, K0FG

  • Jeff_W4DD
    Jeff_W4DD Member ✭✭

    I'm not so sure this is a CW only problem. About once every 100 or so transmissions I have a similar problem on SSB. Both PTT (footswitch) and audio go directly into the back of the radio. When I PTT, the radio goes into Tx, the audio level meter on the Flex bounces as I speak and hits -10. However, the RF power output on the Flex Tx panel stays at zero, as does the external watt meter. The other station never hears my transmission. It will remain in that condition as long as I stay in PTT, but if I release the footswitch and start again, everything is normal. I haven't found anything that causes this to happen. It appears totally random. The 6600 is presently on version 3.2. This sounds somewhat similar to the missing CW drop out problem.

  • K0FG_Fred
    K0FG_Fred Member ✭✭

    I just installed ver 3.4.21 and it may have helped the CW missing dits and dahs problem. Have only made 10-12 contacts with the new ver but all the cw seemed to be fine so far.

    Except. Now every time I xmit cw the cw speed goes to 22-24wpm. No matter what I set it to as soon as I xmit the speed goes back to 22-24 and it xmits at that speed and then stays at that speed until I crank it to a different speed.

    What fun we are having.

    Fred, K0FG

  • Lasse SM5GLC
    Lasse SM5GLC Member ✭✭✭

    Fred, do you by any chance have a logging program running? If it has the ability to send CW messages it usually can set the speed, and thus be in conflict with speed setting through SSDR.

    /Lasse SM5GLC

  • Chris Long
    Chris Long Member
    edited February 20
    I am seeing the same issue, with both CW (paddle) and SSB. I am running 3.4.21 as of today, but saw the issue in 3.3.33. I can reproduce the CW drop every time, without fail, by sending a series of dots. It will transmit them for a period of time depending on the CW speed setting, then the RF output will go to zero, but the MOX is still lit and the sidetone is still running. At 15 WPM, the drops happens after 20 seconds. At 20 WPM it is 16s, at 25 WPM it is 13s, at 30 WPM it is 11s, at 35 WPM it is 9s, and at 40 WPM it is 7s. This is dead repeatable. Interestingly, if you alternate dots and dashes, the time increases to 18s at 25 WPM, with similar times related to CW speed as with just dots. I have to drop the keying to let the radio return the Rx mode, then it will start putting out power again, as others have observed. The issue happens with either the barefoot rig into a dummy load, or with the PGXL into a load, or over the air, at any power level. The antenna is a DB18E at 60 feet, about 150 feet from the operating point. I key the Maestro in SmartControl mode using a set of paddles. On SSB I have not found a speech pattern that causes this to happen consistently, but the behavior is the same - RF output goes to zero but every other indicator is that the radio is still transmitting. I am using an external RF power meter to confirm the power drops. CW is set for breakin, iambic, and a delay of 200. The drop time stays the same regardless of the delay setting. I tested a delay range from 1 to 400, and the drop times stayed the same. I have not yet tested this using the CWX macros. Whatever this is is really consistent based on the paddle input, as far as I have been able to determine. Hope that this helps find the bug.

    Chris, N1CL
  • K9SO
    K9SO Member ✭✭

    I also have been experiencing this issue. I have an open ticket #57277 regarding the problem



  • K9SO
    K9SO Member ✭✭

    As mentioned before, the fault appears here randomly. It is associated with manual keying (external keyer) and is associated with speed of that keyer. If TX delay is set high (40mS or so) when the issue appears, keying speeds are limited to 15 wpm or so. Faster speeds and we get RF dropouts.

    I have sent an audio file to Ken in association with my ticket (57277). Decreasing the TX delay allows faster CW keying so those two settings are correlated.

    While playing with those settings, the problem mysteriously went away. But it will return.

    One must listen to the transmitted signal on another radio to identify the problem since the local sidetones sound just fine. Rebooting and/or restarting has no effect.


    K9SO (or sometimes K9SM or N9ST when sending on my 6600)

  • Chris Long
    Chris Long Member
    edited February 20
    I too have this issue, starting at least on 3.3.33, when I started doing more CW. I am running 3.4.21 and the issue remains. I can make it happen every time by sending an unbroken string of dots. The MOX will drop, sidetone drops, no output present in the waterfall, RF output goes to zero (confirmed with power meter). The radio appears to be in Rx mode, and will not recover until keying is stopped for a moment. Keying done through Maestro in SmartControl mode, paddles into the Maestro. Power does not make a difference: 1w to 100w on the radio, 1KW on the PGXL, on-air, or dummy load, same behavior. I have not observed this to happen using the CWX macros (mine are pretty short, <5s), but have not tested this extensively.

    The PC is running Windows 11, with the latest updates (as of 2/19/2023).

    Further testing shows a direct relationship between the CW keying rate and the time it takes for this dropout to occur. Furthermore, using alternating dot-dash increases the time to increase by just about 50%. The following shows the time to drop vs. CW rate, in seconds, for just dots and alternating dot-dash:

    WPM Dots Dot-Dash
    10 31 46
    15 21 32
    20 16 24
    25 13 19
    30 11 16
    35 9 14
    40 8 12

    Changing the delay has no effect. I tested delays from 1 to 400, no change. Here are some other things tested/observed and the results:

    Frstack3 running or not, same behavior

    Iambic on/off has no effect

    DAX on/off on Rx has no effect

    Sidetone on/off has no effect

    Tx timeout tested from 0 to 1000, no effect

    CW a or b, no effect

    CWU or CWL, no effect

    CWX sync on/off, no effect

    Mute local audio when remote disabled, no effect

    CW filter low latency or sharp, no effect

    Network monitor shows no packets dropped or change in stats when issue happens

    Spots disabled, no effect

    Disconnect Maestro and re-enter in SmartControl mode, no effect

    Doing a complete hard reboot of the Maestro, no effect

    Show Tx in waterfall enabled/disabled, no effect

    In SSB, a very similar issue is present, but the behavior is slightly different. Here, using VOX mode, the MOX will stay on, audio input is showing on the meter, but the RF output goes to zero, and no Tx signal shows in the waterfall. You must drop the VOX for a moment and then re-VOX to get the RF output back. I have not been able to find a speech pattern that will generate the same precise time to drop as in CW, but having the vox disengage for a split second a few times in a row appears to make it happen more quickly.

    Hopefully this will help the collective find a solution to the very annoying issue.

    Chris, N1CL
  • KD0RC
    KD0RC Member, Super Elmer Moderator

    Hi Chris, I tried your experiment without a Maestro and can't get it to drop any characters.

    My setup:
    Flex 6400 at 1 watt to a dummy load on Ant 2
    Speed 25 - 100 WPM
    Delay 0 - 2000 ms
    Paddles to Key line on the back of the radio
    External keyer connected to pins 4 & 5 of the accessory jack on the radio
    External keyer using the API to key the radio via the ethernet cable

    All three keying methods give exactly the same results with or without the sidetone engaged.

    I did this experiment to help narrow down Maestro vs radio issues.

    Is your Maestro on your LAN or connected remotely using SmartLink?

  • Chris Long
    Chris Long Member
    It is on my LAN.
  • K0FG_Fred
    K0FG_Fred Member ✭✭

    To answer your question Lasse yes I do have a logging program running and I was sending messages from Writelog when the change in cw speed occurred. Writelog can change the speed at which it sends cw to the computer and to the radio, but I did not know that it could change the wpm display on the 6400M.

    I set the speed to 30wpm on the Flex and the display briefly shows 30wpm. Then I send a message using Writelog and the message speed is set at 22wpm. Writelog sends at 22wpm, as it should and the radio xmits at 22wpm, as it should. But if I touch the cw speed knob on the radio it now shows 22wpm. I did not know that Writelog would change the speed setting displayed on the radio. Evidently the Flex driver for Writelog is very tightly integrated with the radio.

    I believe all is working as it should, my concern was how did the speed knob on the radio get set to 22wpm?

    Fred, K0FG

  • Mal G3PDH
    Mal G3PDH Member ✭✭

    Fred, I think you will find that when sending macros from a logging program the speed is determined by that. It is the same when using N1MM, the radio CW speed control has nothing to do with it, only if using the internal keyer with manual keying. They keying problem that you described on an earlier post during a contest does not sound like this issue but something very amiss with the keying function for whatever reason. Apart from the RF drop out I have no issues with the actual keying characteristics of my Flex 6500.

    There have been a lot of responses now regarding this RF drop out problem and I have also been feeding back to Ken Well for Flex. However, my situation is that with the latest 3.4.21 software I only experience the RF drop out very infrequently and am having difficulty in recreating the fault in order to carry out testing and therefore unable to feed much back. Hopefully the post from Chris N1CL will assist Flex in finding the fault as he seems to be able to recreate it on demand, even with the latest software.

    It’s a real mystery and I know mine will do it again eventually but despite several long CW QSO’s I just cannot seem to bring it on at the moment.

    73 de Mal G3PDH

  • K1ESE
    K1ESE Member ✭✭✭

    If I am using an external keyer connected to the accessory port, does the Speed slider on the "P/CW" box of the control panel make any difference?

    The manual says -

    "In CW mode, the FSK/Key input on the rear panel accessory connector (pin 4) can be used as a straight key input. This is useful if you wish to attach an external keyer, such as a K1EL WinKeyer, microHAM microKEYER, or another contest-oriented interface. This input is always active and is not affected by the FLEX-6000 internal keyer settings."


  • Mal G3PDH
    Mal G3PDH Member ✭✭

    Just a further note having read the post from Chris N1CL in more detail. Chris seems to state that the keyed sidetone also drops. When the CW RF drop happens with my set up the sidetone definitely keeps going in line with the keying and that is why the drop out is not noticed easily unless spotted on the rig or other power meter. Also, in the drop out state the radio does not seem to be in proper RX mode as the S meter does not show any RX signal. The radio seems to be in a semi-RX state and does not go int proper RX mode until the delay time setting kicks in.

    Mal G3PDH

  • Lasse SM5GLC
    Lasse SM5GLC Member ✭✭✭

    As I am sticking to 2.4.10 I have not much to add. But if the problem is less frequent on 3.4.21 I guess one way would be to start looking at other versions that have more frequent incidents i.e. 2.8.1. This way it would be easier to isolate the core reason and then verify on 3.4.21. But not beeing a s/w guy I'm just rambling :)

    /Lasse SM5GLC

  • K9SO
    K9SO Member ✭✭

    In my case, I was sending a series of 'dahs' from an external keyer as a test. I was using that keying input to assert PTT (or break-in MOX). As I increased keyer speed, I started to get RF dropouts.

    I was also using Ethernet to assert PTT to a PowerGenius.

    I did not see the dropouts when asserting PTT via an external mode like a footswitch so that was a clue.

    There seems to be two interacting settings that may be causing this:

    Under settings>>radio setup>>TX, the TX delay setting delays the actual RF by that amount. In my case, the setting was at 30mS.

    On the P/CW panel on the main screen, there is a slider labeled DELAY. This slider only appears when in CW mode and should be more appropriately labeled HANG TIME. It does not delay the CW, but rather it holds the PTT (MOX) after sending is complete (like a VOX function). CW becomes more 'semi-break-in' rather than full. When I was experiencing the RF dropout problem, I had that DELAY (i.e, HANG TIME) setting below 30mS

    An interesting situation arises at high speed CW (again external keyer only). The contact closure at the radio keying input may actually be released before the RF is finished sending. For example, a 'dit' may be only 30mS long at high speed and if TX delay is at 30mS, the software needs to hold MOX until the actual transmission is actually complete. If the DELAY setting in the P/CW panel is too low, a protection algorithm may be triggered.

    Add in the additional confusion of Ethernet PTT to the amplifier and this timing issue rapidly gets complex. A miss key of the amplifier may also trigger a protection.

    I seem to have solved this by asserting PTT to the amplifier via an RCA jack (with zero delay), setting TX DELAY in settings to 30mS, and DELAY in the P/CW panel to >200mS. I also noticed that there may be a persistence issue and SmartSDR may need to restart after making these adjustments.

    I wonder if anyone else can confirm this.


    Fred, K9SO

  • Ken Wells
    Ken Wells Community Manager admin
    edited February 23


    If you are using an external keyer connected to either the AUX port or the Key Input port, the CW Speed control on the P/CW has no effect on the Keying speed.

    HOWEVER, there are two "zones" in the CW Speed control that set the CW signal Rise-time and Decay time.

    Below 31 WPM, the rise & fall time of the CW signal is about 8 ms.

    31 and above WPM the rise and fall times are set to about 6 ms.

    (These rise & fall times are also set the same way when using the internal keyer)

    (This is the current status in version 3.4.1 and previous versions for several years)

  • K1ESE
    K1ESE Member ✭✭✭

    @Ken Wells

    I think you are saying it makes no difference whether you plug an external keyer into either the AUX port or the Key Input port in any way.

    The only parameter for CW that changes with an external keyer is how you set the Speed control in SSDR and only then for CW rise and fall timing.

    Thanks for the clarification.


  • John, G3WKL
    John, G3WKL Member ✭✭

    Just to add that I also have experienced this problem and agree with the Flex configurations when it can occur. I've posted this as I use a 6700 and like Roger, v2.8.1

    73 John, G3WKL

  • Keith - N8CEP
    Keith - N8CEP Member ✭✭
    edited February 27


  • Keith - N8CEP
    Keith - N8CEP Member ✭✭

    I find the fact that these problems have not been adressed (or fixed yet) very troubling. Should I wait for a fix or sell my Flex?

  • Trucker
    Trucker Member ✭✭✭

    Unless you are unhappy with other parts of your radio, and CW is not the only mode you use, I would not personally, want to sell my radio in that case. There are other things in the radio that work just fine. And other things that need attention. That is not uncommon with any radio, SDR or otherwise.



  • k3Tim
    k3Tim Member ✭✭✭

    Running a 6500 while trying to recreate this CW problem but unable. Paddle plugged into front panel jack sends perfectly.

    A manual key / bug connected to the CW-FSK (pin 4) on the rear panel is a different story. Sometimes the 6500 does not xmit even though the key/bug had grounded this pin. A VOM confirmed the pin was grounded but no RF. Someone had posted this behavior previously but I can't find it. Using a "BUG DESCRATCHER III" to connect the manual keys to pin-4 fixed this problem. The descratcher is an electronic circuit to remove contact bounce. A search of the term (in caps) will lead to a complete description. It would seem the logic to debounce pin 4 needs refinement or the user side must generate a de-bounced signals. Interestingly, the front panel paddle jack does not display this behavior. 

    Tested using low RF out, Full-break-in, no delay, 250m-sec hang-timed, FDX, HDX, 20-WPM, 35 WPM, barefoot/no-amp.

    SW information:

    Smart SDR Version

    MS Windows 10 Pro

     10.0.19045 N/A Build 19045


    k3Tim / 7

  • Mark K0LO
    Mark K0LO Member ✭✭
    edited March 1
    Here's an additional bit of data to add. I noticed that this same problem also occurs when operating on FT4 or FT8. I normally operate with a separate receive antenna that is far enough from the transmit antenna that my transmitter doesn't overload the receiver. So I can see other stations transmitting while I'm transmitting.
    Occasionally during an FT4/FT8 transmission I would see my carrier drop out briefly and then come back on. It was not that frequent of an occurrence; most transmissions would last the full 7.5 or 15 second transmit interval without dropout. But it occurred often enough to be noticeable.

    So this problem may not be limited exclusively to CW operation.
  • Mark K0LO
    Mark K0LO Member ✭✭
    To add to this discussion, besides CW being affected, I've also noticed this effect when operating on FT4/FT8. I normally operate with a separate receive antenna that is far enough from the transmit antenna that it doesn't overload the receiver. While transmitting, I can see my own signal as well as other stations in the passband.
    Occasionally I see my transmit signal drop out for a few hundred milliseconds during the 7.5 /15 second transmit interval. It's relatively infrequent; most transmissions complete without dropout. But it happens often enough to get your attention.
    So perhaps this issue is not limited to only CW.
  • K0FG_Fred
    K0FG_Fred Member ✭✭

    For the cw contest over the weekend my 6400M was sending cw so erratically I had to turn it off and bring out the Elecraft K3S, which sends code perfectly.

    Have paddles plugged into key jack and 3 straight keys plugged into the acc plug on pins 4 and 10.

    Sometimes the closure of the key does not generate xmit on the radio, regardless of which key input I am using. And sometimes it inserts a space between the cw elements, sent my callsign 3 times to one station as my radio twice xmited 'e r' rather than f when using the F1 key. Was not caused by my poor fist.

    Judging by the comments on this board it sounds like this has been a problem for quite some time. And Flex either cannot or will not fix the problem. Is cw used by so few ops that Flex has little incentive to fix this? I talked to someone at Flex a few months ago and they said this problem is not on their short list of problems to be addressed. Gives me little incentive to keep the radio.

    Name another brand of radio in the ham market that does not send good cw. Would Flex jump on this problem if it were an FT8 issue?

    Since cw is my primary mode I guess I will have to get rid of my 6400M and keep the Elecraft. Too bad cuz I really like learning the Flex and all it's possibilities but at my age I am more interested in learning to use and operate the radio than I am in listening to excuses.

    The cw issue and the issue with losing tx profiles are large detractions from the love of this radio.

    The 6400M will soon be posted on the swap meet section of this board. I hope nobody wants to buy it to work cw.

    Fred, K0FG

  • Mal G3PDH
    Mal G3PDH Member ✭✭

    Fred, The problem that you are describing is something totally different to the intermittent CW RF drop out problem. There is something obviously fundamentally wrong somewhere in your station set up which sounds very unusual. The Flex rigs send nice CW and I have no issue about the actual keying which is perfect. It is just the intermittent RF drop out which needs fixing and hopefully they are now working on it. Unfortunately it is difficult to simulate as it is so random. So do not judge the radio on the problem that you are experiencing as I am sure that can be tracked down and fixed. The radio itself is excellent.


    Mal G3PDH

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