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Low Power Output? 6300 or 6500

Steve N4LQSteve N4LQ Member
edited June 23 in SmartSDR for Windows
With  both my 6300 and 6500 they struggle to produce over 85 watts. 
Using the same DC supply and watt meter my other rigs easily do 100 watts. 
So am I the only one or have others noticed this?

I'm not interested in how small the DB difference is either. I just want to know.

Completed · Last Updated



  • Jim GilliamJim Gilliam Member
    edited September 2018
    if you have a calculator it is 10*log80/100. This will be a negative number and the number of dB down it would be. My calculator gives -.969 dB. almost 1 dB down.
  • Jim GilliamJim Gilliam Member
    edited September 2018

    My 6500 reads 105 Watts out. My Bird Watt meter reads 108 Watts forward and about 5 Watts reflected which means the output power of the transmitter is 103 Watts. This is without the tuner.


  • KY6LA_HowardKY6LA_Howard La Jolla, CA. Paris and Sablet FranceMember ✭✭✭
    edited January 2017

    I easily get 100W out of my 6700 but I use a 50A power supply and very short 8 gauge power cables.

    Have you measured the voltage at the INPUT to your 6500 under transmit conditions.

    I suspect that you have too low a supply voltage at the input and/or your voltage drop in your cables is causing your issue.

  • Barry IsseksBarry Isseks Member ✭✭
    edited July 2015
    My 6300 and 6500 both put out full power.. 100w+/-  into low SWR loads.
  • Steve N4LQSteve N4LQ Member
    edited September 2015
    I'm measuring 13.55 volts at the rig, key down at full output, 88 watts. Shouldn't that be enough? 
  • KY6LA_HowardKY6LA_Howard La Jolla, CA. Paris and Sablet FranceMember ✭✭✭
    edited January 2017
    12V DC is usually defined as meaning actually 13.8V
  • Duane_AC5AADuane_AC5AA Member ✭✭
    edited May 2018
    Steve, my readings checked tonight with 6500 -> PowerMaster -> Palstar HF-Auto (bypassed) -> Dummy load:

    A = PowerMaster reading (set for full forward power reading), 
    B = Palstar HF-Auto power meter:

    Band        A          B     
    --------     -----     ------
    160m     98.3      90
      80m     98.9      92
      40m     95.0      89
      30m   101         92
      20m     97.7      92
      17m   103       101
      15m     88.6      87
      12m     96.6      99
      10m    92.3       89
        6m     n/a      104*

    * probably inaccurate at this freq.

    Hope this helps. My 6500 is almost exactly a year old.

       73, Duane

  • W5XZ - danW5XZ - dan Member ✭✭
    edited June 2019
    you're not the only one, my 6500 is a little soft of 100w also, w a 35 amp pwr supply..

    seems odd, since the rd100's are good for 100 w a piece...and there's a pair, in push pull..

    i know there's hardware rf negative feedback, but suspect the calibration routine..

    I'd be a happy camper if mine put out 125 w easy, all bands..

  • k3Timk3Tim Member ✭✭
    edited June 2
    The DC power spec says:
    • Power Supply Requirements:  +13.8V DC nominal ±15%
    At this station we run 14.0V with a 8" pigtail (12 gauge) and see 100 watts consistently on the meter.

  • Ed, K0KCEd, K0KC Member
    edited September 2017
    When measuring the DC at the input to the radio, it is difficult to make contact with the PowerPole connectors with DMM probes. My solution was to use a couple of sewing needles to make contact and then touching the needles with the DMM probes.

    It is hard to believe, but I will have had my 6700 for two years next month (probably means I will experience a non-warranty failure this summer). I noticed the low power output issue early on and it was cured by a short vacation in Austin for a re-calibration.

    The length and gauge of the power cables are certainly important, but another factor to consider is the resistance of a PowerPole connector; it is even worse if you use some distribution system such as a RigRunner.

    Ed, K0KC
  • Steve N4LQSteve N4LQ Member
    edited September 2015
    I can just see me chopping off my power lead to 8". 
  • Greg LeberGreg Leber Member
    edited May 2015
    Had the same problem with a different rig found there was a voltage drop in my MFJ power ****. Connected straight to power supply an back to full power!
  • wb4dwdwb4dwd Member
    edited December 2018
    80-82 watts is all my 6300 will do.  Tried every band and a 20 and a 45 amp power supply and a dummy load. .   My ACOM amp can't tolerate more than 30-50 watts, so I haven't bothered with it. 
  • DrTeethDrTeeth Member ✭✭
    edited August 2016
    Similar here. Never seen 100W even with 14v when txing, into a 1:1 swr antenna.
  • PatrickPatrick WH6HI Member ✭✭✭
    edited June 2016
    Queation:  Are these measurements being done with a good Resistive Load or antenna?  No antenna is purely resistive and the reactive parts have a bearing on the output of the transmitter. 
  • Steve N4LQSteve N4LQ Member
    edited September 2015
    Doesn't matter. 50 ohm resistive or reactive, it's always low. 
    No it's not the power supply....Same one for other rigs.
    No it's not the cable....Checked with DVM

  • Steve N4LQSteve N4LQ Member
    edited September 2015
    So we're "calibrating" rigs now so we can get rated power? 
    Can't it calibrate itself? I claims to be doing that when I turn it on. 
  • Ed, K0KCEd, K0KC Member
    edited May 2015

    The "calibration" that I mentioned above was completed at the Flex facility in Austin after several conversations with Dudley in Technical Support. The calibration that the radio performs on startup is something different as far as I know.

    Ed, K0KC
  • George Molnar, KF2TGeorge Molnar, KF2T Member ✭✭✭
    edited February 2019
    Did some experimenting. Yes, the input voltage is the culprit (at least here). If at all possible, shorten your leads as much as you can. Check connectors. With a single cleanup of one not-so-expertly installed PowerPole, I came back up to 100w on the button.
  • Bill -VA3WTBBill -VA3WTB Member ✭✭✭
    edited February 2018
    George, it must be something like what you say, most people are getting 100W   I am
  • Steve N4LQSteve N4LQ Member
    edited December 2018
    I'm using the power cable that came with the 6500. Before that I used the power cable that came with the 6300. Both have low power. At one point Flex stated that a firmware update would cure the problem. It helped a little but not much. Again. I'm getting 13.55v at the radio. I might be able to adjust the PSU up to 13.8. Is it really that critical on these rigs?  You would think there would be some wiggle room.
  • Reggie-k6xrReggie-k6xr Member
    edited April 28
    I have 14.0 volts delivered to the connector on back of flex 6500. 80 to15 is 85 watts. 17=100,  21 to 28=95. into dummy load and on air.

  • DrTeethDrTeeth Member ✭✭
    edited August 2016
    Changing the supplied voltage a few 1/10V does not change anything much. I just experiemneted for those who mentioned the voltage drop on key down condx.
  • Steve N4LQSteve N4LQ Member
    edited December 2018
    From reading these post I now believe there must be at least 50% out there with low power. 
    Wonder what the problem really is? Can it be fixed in software? What is "calibration"? 
  • Jim GilliamJim Gilliam Member
    edited September 2018

    Have you double checked your power output with an external power meter? It could be the readings on the internal meter are software-driven and could be giving erroneous readings. Also, the tuner will exhibit some loss. Remember if you have an SWR that the power delivered by the source (transmitter) is the forward power minus the reflected power.

    Jim, K6QE

  • DrTeethDrTeeth Member ✭✭
    edited August 2016
    Let's hope that the 'calibration' is not keeping the output the same but making the meter read 100W, hi hi.

    FWIW, I use the voltage readout from DDUtil which takes into account cable length and resistive connections.
  • Steve N4LQSteve N4LQ Member
    edited September 2015
    Believe us. It's low. 
  • k3Timk3Tim Member ✭✭
    edited December 2016

    Hi Burt,


    Yes - the plural -  The?/My? XYL just passed General Class exam.  Extremely proud of her as she is Business Major in College and by profession.  She passed Tech with a lot of study but seems over the basics now and passed General w/o as much effort it seems (although a lot of study non the less).  97% passing score on both exams.  She's now going for Extra Class....

    Sharing the station (6500) with her, of course, hence "we".  Maybe time for a 6700 with dial receiver.  

    Best Regards,

  • DrTeethDrTeeth Member ✭✭
    edited August 2016

    Mni congrats to the XYL. Sharing a rig won't last for long...then there will be the mutual RFI/QRM. Opened a can of worms, Hi hi?
  • Steve K9ZWSteve K9ZW Member ✭✭✭
    edited December 2018

    Early on with the Flex-6700 I found unexplained lower output times.  The power supply "should" have not been the issue, as it was above spec and metering didn't indicate it as the issue.

    Switching to a slightly larger power supply 100% corrected the issue.  Suspicion centers on the apparently marginal power supply slightly dropping voltage - drooping if you prefer - at the key up moment, which the radio was sensitive to enough to limit output.

    The oversized power supply corrected low output of the Flex-6700.

    Mobile with the Flex-6300 I have used another oversized power supply with no noted issues.





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