6500 power

Bill -VA3WTB

Good point Steve,  Technically challenged?

Walt - KZ1F

That's why the intent was pejorative. IMHO. But who's counting?

HCampbell WB4IVF

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

 

Gerald-K5SDR

[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review was done we have slowed the rise time down based on recommendations from Rob Sherwood so QST review is totally out of date.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

Gerald-K5SDR

[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

k3Tim

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"

HCampbell WB4IVF

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. 

Gerald-K5SDR

@Salvador

In reference to your post.

I only need about 10 to 20w to drive my expert amps... am I better of running a dedicated PSU at 15v even if I only want 20w out of the Flex than a 13.8v PSU?

If you are running low power drive, the added voltage won't much if any difference.  It does make a difference when you are running into compression at full power output. 

Bill -VA3WTB

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.

W5XZ - dan

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

Gerald-K5SDR

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.  

W5XZ - dan

ok, then here's a vote for "110" ( or more ), from software.

thanks, gerald
 

Stefano - W2WTZ

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.

Ken - NM9P

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.

Ken - NM9P

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.

Tim - W4TME

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.

Gerald-K5SDR

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.

Stefano - W2WTZ

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.