6500 power

  • 6
  • Question
  • Updated 3 years ago
  • Answered
The power meter on my 6500 shows a maximum of 85W. I checked with LS2K4 Wattmeter that is a little bit more accurate than a bird and tha value is correct. Power supply gives 13,53V. Why my Flex doesn't give full power ouput? The specifications says 100W if am not wrong. I read some posts on the same matter but I didn't undestood if this is a general problem, there is a fault on my 6500 or what else. 15W missing on 100W it's a lot...
Photo of Stefano - W2WTZ

Stefano - W2WTZ

  • 82 Posts
  • 20 Reply Likes

Posted 3 years ago

  • 6
Photo of K3ZJ - Dave

K3ZJ - Dave

  • 41 Posts
  • 5 Reply Likes
FACT CHECK.  Amateur transceivers using 13.8v devices can and do produce 100 watts output with cleaner signals than the Flex-6700 at its lesser power.  Identical testing at the ARRL Lab demonstrates this fact. The Elecraft K3 ARRL test running 100 watts on 14 MHz is at figure 2 in the K3 QST product review published January, 2009. The same test for the Flex-6700 is at 87 watts on 14 MHz at figure 5 in the QST product review published April, 2015.  The K3 tested is a 2008 K3, years before the 2015 synthesizer improvements.  The original K3 transmitter is about 14 dB better at 2 kHz than the Flex, and maintains a clear advantage throughout the 10 kHz shown (5 kHz either side of the signal).  It's misleading (at best) to state or suggest otherwise. (In the ARRL review, the note on p.51 under "Transmitter", Power output", clearly states that spec is 100 watts output but that in the ARRL lab output varied between 87-99 watts; on 6 meters it was 82 watts.  You can compare these charts with any other radio reviewed recently by the ARRL.  The facts are in the measurements and charts.
Photo of Gerald - K5SDR

Gerald - K5SDR, Employee

  • 822 Posts
  • 1476 Reply Likes
[I am posting this in two places because there are two references to the same comparison]

It is important to note that CW keying sidebands (Figure 2) have nothing to do with PA linearity or power output.  CW and RTTY are not linear modes and can even be run in Class C with no problem.  CW keying sidebands are generated strictly by the rise time characteristics of the keying waveform.  The faster the rise time, the wider the bandwidth.   Since the ARRL review was done we have slowed the rise time down based on recommendations from Rob Sherwood so QST review is totally out of date.  The CW rise time and wave shape is strictly a software controlled function and can easily be changed.  

For linear operation (SSB, PSK, etc.) you need to compare the "Third-order intermodulation distortion (IMD) products" under the Transmitter section.  Note that the K3 was shown to be adjustable to 116W.  That is what I mean by letting the control go above 100W, which we could do to without re-calibration.

The direct comparison for IMD between the K3 and 6700 are copied below from the respective QST reviews for for the worst case band 3rd/5th/7th/9th order TX IMD are:

K3: -29/-43/-46/-51
6700: -32/-51/-52/-52

This is the relevant comparison for the context of power output vs IMD.  CW keying bandwidth is a totally different subject.

Gerald
Photo of k3Tim

k3Tim

  • 865 Posts
  • 170 Reply Likes
IMD :  -45
The IMD of 6500 at this station, using 100W to dummy load and digital two tone s/w program driving the DaX channel is is -45dB .  The FDX mode of 6500 was used to capture the test results.

FYI - a Special Event station in VK-land provided an unsolicited "great audio"
(Edited)
Photo of Stefano - W2WTZ

Stefano - W2WTZ

  • 82 Posts
  • 20 Reply Likes
David.....ARRL lab uses unsophisticated intruments in the hand of unsophisticated EE. Now II am glad that if my 6500 is in reality 100W,my 991 is 115W. Only Flex takes care of purity emissioni, rest of unsophisticated producer of 100W radios don't know that it's impossibile to reach this power with a clean radio.Flex knowing we are not prepared to accept this truth, avoid to indicate in the catalogue, read only by unsophisticated buyer, whose money is not so unsophisticated.
Photo of Walt - KZ1F

Walt - KZ1F

  • 3040 Posts
  • 644 Reply Likes
You do realize, don't you that colloquially unsophisticated equals rube.
Photo of HCampbell  WB4IVF

HCampbell WB4IVF

  • 220 Posts
  • 53 Reply Likes

The K3 has exceptionally clean keying sidebands, among the best if not the best from what I read, but there was much more to the ARRL tx testing.  I would also consider the other test results. 

 For another perspective, here’s a link to Adam Farson/AB4OJ’s test report site, which contains his Flex 6700 test report (note that tx testing was conducted at 100W):

http://www.ab4oj.com/test/reports.html

BTW, Adam also has a new presentation on the site (under Test Methods and Procedures): A New Look at SDR [receiver] Testing

Update:

I just did a quick search here and found this very interesting discussion:

 https://community.flexradio.com/flexradio/topics/flex-6700-v-elecraft-k3-cw-bandwidth-measurements

 

(Edited)
Photo of Gerald - K5SDR

Gerald - K5SDR, Employee

  • 822 Posts
  • 1476 Reply Likes
[I am posting this in two places because there are two references to the same comparison]

It is important to note that CW keying sidebands (Figure 2) have nothing to do with PA linearity or power output.  CW and RTTY are not linear modes and can even be run in Class C with no problem.  CW keying sidebands are generated strictly by the rise time characteristics of the keying waveform.  The faster the rise time, the wider the bandwidth.   Since the ARRL review was done we have slowed the rise time down based on recommendations from Rob Sherwood so QST review is totally out of date.  The CW rise time and wave shape is strictly a software controlled function and can easily be changed.  

For linear operation (SSB, PSK, etc.) you need to compare the "Third-order intermodulation distortion (IMD) products" under the Transmitter section.  Note that the K3 was shown to be adjustable to 116W.  That is what I mean by letting the control go above 100W, which we could do to without re-calibration.

The direct comparison for IMD between the K3 and 6700 are copied below from the respective QST reviews for for the worst case band 3rd/5th/7th/9th order TX IMD are:

K3: -29/-43/-46/-51
6700: -32/-51/-52/-52

This is the relevant comparison for the context of power output vs IMD.  CW keying bandwidth is a totally different subject.

Gerald
Photo of HCampbell  WB4IVF

HCampbell WB4IVF

  • 220 Posts
  • 53 Reply Likes

If Flex goes to “11”, someone is likely to notice/report increased IMD the next time the radio is tested, and here we go again.  My vote would be to keep it as is, and maybe expand a little in the documentation, as has been suggested.  Not a big deal to me either way.  Other future updates are much more important to me. 

Photo of Bill -VA3WTB

Bill -VA3WTB

  • 3178 Posts
  • 706 Reply Likes
More companies should take Flex lead on this. I hardly think this is effecting sales. I can't prove this, but I bet 95% of owners care less about it as most use an amp anyways. But this has given a few a reason to take Gerald to task over it.
Photo of W5XZ - dan

W5XZ - dan

  • 564 Posts
  • 83 Reply Likes
Gerald, can I send my radio in and get it cranked up to 150w?  I very rarely use ssb or digi modes...99.5% cw here...using old fashioned, low gain, grounded grid, tube finals..

unless i'm mis-reading the spec sheet for the RD100HHF ( VERY possible ), these things should be good for 100w a piece, right?  I do appreciate there is negative feedback from drains to gates, but there are 2 devices in push pull.

or, maybe, 'a few lines of code', to put the final in class C on cw, maybe ??

regards, dan, W5XZ
(Edited)
Photo of Gerald - K5SDR

Gerald - K5SDR, Employee

  • 822 Posts
  • 1476 Reply Likes
Dan, in a word no.  That would take you into total saturation at 13.8V, which would be more like class D.  You would need to run the parts at higher voltage than allowed for the rest of the radio, which is limited to 16V max.  
Photo of W5XZ - dan

W5XZ - dan

  • 564 Posts
  • 83 Reply Likes
ok, then here's a vote for "110" ( or more ), from software.

thanks, gerald
 
Photo of Ken - NM9P

Ken - NM9P, Elmer

  • 4067 Posts
  • 1266 Reply Likes
Gerald, I would cast my vote to keep the TX Cleaner, even at the expense of a few Watts...  at least until adaptive predistortion makes it possible to tweak a little more power out cleanly (If that is possible).  If the dial goes to "11" there are going to be those who will always run full throttle no matter what the effect upon their signals, or their neighbors.  That would be bad for the hobby, and bad for the reputation of Flexradio.
Photo of Ken - NM9P

Ken - NM9P, Elmer

  • 4067 Posts
  • 1266 Reply Likes
Gerald, I would cast my vote to keep the TX Cleaner, even at the expense of a few Watts...  at least until adaptive predistortion makes it possible to tweak a little more power out cleanly (If that is possible).  If the dial goes to "11" there are going to be those who will always run full throttle no matter what the effect upon their signals, or their neighbors.  That would be bad for the hobby, and bad for the reputation of Flexradio.
Photo of Stefano - W2WTZ

Stefano - W2WTZ

  • 82 Posts
  • 20 Reply Likes
DDutil gives me 13,9V, on front display of 6500 the first two numbers I read are 13.62 - 13.46. Which is the correct voltage that arrives at the radio? What represents all the numbers I see on display?
Gerald, thank you once more for your contribute. Pls evaluate to leave the adjustments as they are and instead modify the technical specifications in the way they are written.
Photo of Tim - W4TME

Tim - W4TME, Customer Experience Manager

  • 9153 Posts
  • 3495 Reply Likes
The first voltage value is the voltage before the main fuse.  The second voltage is after the main fuse.  Always expect the 2nd voltage value to be less than the first.
Photo of Gerald - K5SDR

Gerald - K5SDR, Employee

  • 822 Posts
  • 1476 Reply Likes
The first voltage value is the one that is closest (but not exact due to IR drops) to the value seen by the PA transistors.  This is after the 30A fuse on the input of the PA.  the second number is after the 5A fuse on the transceiver board.
Photo of Stefano - W2WTZ

Stefano - W2WTZ

  • 82 Posts
  • 20 Reply Likes
Thank you boh for explanation. If I well understood, I should read 13,8v in the first field in order to get full power from PA board right? I wish to supply correct voltage to PA, then place the radio in FM and pressing ptt, power out a dummy load with swr less than 1,03:1.My wattmeter has an accuracy of +/- 5% in worst case. This means that if I read a power out of about 90/92W in all the bands, my Flex works well and it's not necessary to open any ticket I hope.