6600M transmitter stops intermittently on CW

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  • Problem
  • Updated 3 months ago
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My 6600M running the latest version of V 3.x software started exhibiting intermittent transmit failures during the SKCC WES CW contest yesterday.  Specifically, I would be sending and during a dash (key down, transmitter transmitting) the RF output from the 6600M would drop to zero.  Letting the key up and then pressing it down again to sent the next character caused the transmitter to come back on.  However, as long as I held the key down, the RF would stay off.

My setup is a 6600M driving an Ameritron ALS 1306 amp driving a dipole.  I have a tuner between the amp and the antenna but it is usually in bypass.  

There is an EA4TX remote antenna switch and a logging PC connected to the 6600M via  USB cables.  Neither the switch nor the PC seem to be doing anything when the problem occurs. 

The 6600M is limited to 50 watts output and I have measured that with a separate meter. It's built-in ATU is in bypass, no ALC connection or other feedback to the 6600M is present, the SWR between the 6600M and the amp is about 1.1:1.  SWR to the antenna is 1.3:1.  No measurable common mode current in the shack.  The ambient temp in the shack is about 68F and the 6600M air vents are completely clear and power is steady.  No alarms, lights or error messages appear.

The problem is hard to trap because it occurs only every several hundred characters and the 6600M keeps the amp keyed on so its "transmit light" stays on, just no RF comes out of the 6600M.  It does not matter whether or not the amp is on.  I observed the problem on 20m and 40m bands.  Others weren't tested.

Although it is not very new, the last thing added to the shack is the EA4TX switch and it connects to the 6600M via a USB cable.

I would like some help fixing this because people say I'm missing the occasional letter.
Regards,
Jaimie "Jim" Charlton   AD0AB
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James Charlton

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Posted 3 months ago

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Michael Pitre

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I am having the exact same problem with my Flex6500. Has this been resolved?
(Edited)
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Bill -VA3WTB

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Is the radio running all by itself or is there any other software being used with the radio.?
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Tom W3FRG

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I am also having a similar problem, happens very intermittently, when using SSB with my 6600M, or 6300, running V 3.1.8 SSDR.
RF power out will just shut down with no errors from 6600M, LP-700 or RF Kit Amp.
I have to re-click the VOX, or MOX, buttons to get back to normal operation.


Tom W3FRG
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Tom W3FRG

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I neglected to comment during this anomaly, that the Receive signal also dropped down in level significantly during this RF Power drop out.
However, both Tx & Rx returned when either the VOX or MOX buttons were clicked.
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James Charlton

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In my case with a 6600m, the radio is running all by itself with no other software involved except an N3FJP logger that reads the freq from the radio. It does not key the radio, but it can change the radio's set frequency and mode by clicking on the spotter.

I normally use a paddle with a Winkeyer, but the problem seems to occur even when I'm using a straight key plugged directly into the radio.

The radio drives an Ameritron ALS 1306 amp which drives a tuner that goes through an antenna selector to finally get to the antenna. 

I mention the setup, but I don't think it has anything to do with the problem.

It is almost impossible to trap the problem as it is very rare, but here's what seems to happen.

I am sending CW when on a key down, there is no RF output.  I do know that there is no RF out of the 6600m because its meter indicates that and an external meter also indicates zero output.

The SWR as measured by the transceiver is about 1.2:1 and that is the same as measured on an external meter so, the 6600m is well matched to the amplifier.  The Transceiver's output is set at about 50 watts.

Nothing is hot and the transceiver's fan is not running at full speed.

The RF output from the transceiver will stay at zero as long as the key is held down, but letting it up and pressing it down again - even extremely quickly - will restore normal operation.

That's all I have been able to discover except there is no equivalent issue when operating on SSB.

Jim Charlton   AD0AB

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Michael Pitre

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I am experiencing the exact same problem with or without logger running or other software, the only difference being my radio is a Flex6500 running same version of SmartSDR. It is much less noticeable or non-existent with cw QSK delay set to zero. This happens with or without amplifier running, or whether using internal or external keyer.  I have tried going back to SmartSDR 2.0 with no improvement. 
(Edited)
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Lasse Moell

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Open a ticket so Flex understand the severity of this issue! A number of us have reported this already.
I noticed this more than 7 months ago....
" This issue has been logged as defect number: G7759
At this time the only workaround is to stop sending and allow the radio to transition to RX and then start resending "
See threads:
https://community.flexradio.com/flexradio/topics/i-have-a-problem-with-my-flex-6600-and-power-drop-o...
and
https://community.flexradio.com/flexradio/topics/spuruious-no-power-output



(Edited)
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Lasse Moell

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I have yet to see this happen when using  CWX or letting logging program send. Only when I key using a paddle attached to the radio.
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Tim - W4TME, Customer Experience Manager

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Official Response
This is defect G7759 and it is currently being investigated by the software team.  At this time the workaround is to stop sending and allow the radio to transition to RX and then start resending.
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Mal G3PDH

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Yes,  I have also experienced this intermittently over many months.  It gets tedious constantly watching the power meter to check that power is still going out.  I have had instances in a CW QSO where the other station has started to reply thinking that I have passed it over to him after an abrupt halt to my transmission.  t has nothing to do with antennas, SWR's etc.  I am currently trying to check if it happen whilst operating with the Maestro rather than the PC.  
Using 6500 and PC with Windows 10.
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Tom -WA2TP

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Prospective 6600M buyer. Following.
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Joe N3HEE

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I can confirm that this issue is far worse when hand sending CW with a mechanical key.  I was operating SKCC WES this past weekend with a bug and side swiper and the transmitter dropped out at least a dozen times over my relatively short period of operation.  It made operating more difficult as I had to constantly watch the meters for RF drop outs.

This issue rarely happens when using N1MM to send CW.  It happens occasionally when using the electronic keyer built into the radio.

Looking forward to the next release to fix this defect !